As a result of division, 4 haploid cells are formed. §23
3. Task 5 No.12322
Establish a correspondence between the features of cell division and its type.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
4. Task 5 No.17806
Establish a correspondence between the type of cell and the method of its formation.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
5. Task 5 No.19831
Establish a correspondence between the events occurring with cell nuclei in mitosis and meiosis.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
6. Task 5 No.21641
Establish correspondence between processes, occurring during cell division, and methods of division. For each position given in the first column, select the corresponding position from the second column.
Write down the selected numbers in the table under the corresponding letters.
| A | B | IN | G | D | E |
7. Task 5 No.21683
Establish a correspondence between the processes occurring on different stages life cycle cells: for each position given in the first column, select the corresponding position from the second column.
Write down the selected numbers in the table under the corresponding letters
| A | B | IN | G | D | E |
8. Task 5 No.21867
Establish a correspondence between the processes occurring on different stages life cycle of a cell, and the stages in which these processes occur: for each position given in the first column, select the corresponding position from the second column.
| PROCESSES | LIFE CYCLE STAGES |
|
| A) DNA replication B) formation of a fission spindle B) ribosome assembly |
Meiosis is the division that produces sex cells (in plants, spores). Biological significance of meiosis:
- recombination(mixing of hereditary information)
- reduction(reduction in the number of chromosomes by 2 times).
Differences between meiosis and mitosis based on the results
Tests and assignments
All of the terms below are used to describe meiosis. Define two terms that “fall out” from general list, and write down in the numbers under which they are indicated.
1) bivalents
2) reduction division
3) cloning
4) fertilization
5) crossing over
Answer
1. Establish a correspondence between the methods of cell division and their characteristics: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the correct order.
A) reduction division
B) ensures growth, regeneration
B) daughter cells are identical to the parent
D) four haploid cells are formed
D) increases genetic diversity
E) indirect division
Answer
2. Establish a correspondence between the processes occurring during cell division and the methods of division: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the correct order.
A) ensures the growth and development of the body
B) as a result of division, somatic cells are formed
C) maintains the constancy of the number of chromosomes in the cells of individuals of the same species during sexual reproduction
D) underlies combinative variability
D) is the basis of vegetative reproduction
E) bivalents are formed during fission
Answer
3. Establish a correspondence between the characteristics of the processes and the method of cell division: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the correct order.
A) formation of germ cells in mammals
B) body growth
B) division of the zygote
D) conjugation and crossing over
D) reducing the number of chromosomes by half
Answer
4. Establish a correspondence between the processes and the method of cell division: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the correct order.
A) somatic cell division occurs
B) the chromosome set is halved
C) a new combination of genes is formed
D) conjugation and crossing over occur
D) bivalents are located along the equator of the cell
Answer
5. Establish a correspondence between the processes and methods of division: 1) meiosis, 2) mitosis. Write numbers 1 and 2 in the correct order.
A) bivalents are formed
B) formation of diploid cells occurs
B) the number of chromosomes changes
D) crossing over occurs
D) the content of genetic material does not change
E) there is a divergence of bichromatid chromosomes to the poles of the cell
Answer
6. Establish a correspondence between the characteristics of cell division and its type: 1) Mitosis, 2) Meiosis. Write numbers 1 and 2 in the correct order.
A) occurs in two stages
B) after division, diploid cells are formed
C) the resulting cells have a set of chromosomes and DNA 2n2c
D) accompanied by chromosome conjugation
D) the resulting cells have a set of chromosomes and DNA nc
E) crossing over occurs
Answer
7. Establish a correspondence between the type of cell division and biological significance: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the order corresponding to the letters.
A) genetic stability
B) combinative variability
B) regeneration
D) body growth
D) asexual reproduction
E) sexual reproduction
Answer
8. Establish a correspondence between the characteristics of the process and the methods of cell division: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the order corresponding to the letters.
1) pairs are formed homologous chromosomes
2) homologous chromosomes diverge to the poles
3) conjugation and crossing over occur
4) there is a reduction in the number of chromosomes
5) at the end of the process, two daughter cells are formed
6) the identity of the hereditary information of new cells to the mother cell is maintained
Answer
9. Establish a correspondence between the characteristics of the process and the methods of cell division: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the order corresponding to the letters.
A) cells with the chromosome set nc are formed
B) bichromatid chromosomes diverge to the poles
B) conjugation and crossing over occur
D) the number of chromosomes remains unchanged
D) at the end of the process, four daughter cells are formed
E) reduction in the number of chromosomes
Answer
10. Establish a correspondence between the characteristics and methods of cell division: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the order corresponding to the letters.
A) reduction in the number of chromosomes in a cell
B) the formation of cells identical to the mother
B) formation of somatic cells
D) formation of gametes in animals
D) ensuring the growth of organisms
E) formation of spores in plants
Answer
COLLECTING 11:
A) retains the karyotype of the original cell
Choose the one that suits you best correct option. During meiosis, bichromatid chromosomes move to the poles of the cell in
1) anaphase I division
2) anaphase II division
3) prophase of division I
4) prophase of division II
Answer
Choose one, the most correct option. The first meiotic division is different from the second meiotic division
1) divergence of daughter chromatids into resulting cells
2) divergence of homologous chromosomes and the formation of two haploid cells
3) division into two parts of the primary constriction of chromosomes
4) the formation of two diploid cells
Answer
All of the following characteristics, except two, can be used to characterize the processes and biological significance of meiosis. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) formation of cells with double the number of chromosomes
2) formation of haploid cells
3) formation of bivalents
4) the emergence of new gene combinations
5) appearance more somatic cells
Answer
Look at the picture of cell division and determine (A) its type, (B) the number of chromosomes in the cell shown on the left, and (C) what specific cells are formed in animals as a result of such division. For each letter, select the corresponding term from the list provided.
1) mitosis
2) transcription
3) diploid
4) meiosis
5) direct
6) haploid
7) gamete
8) somatic
Answer
Choose three options. What signs characterize meiosis?
1) the presence of two divisions following one after another
2) the formation of two cells with the same hereditary information
3) divergence of homologous chromosomes into different cells
4) formation of diploid daughter cells
5) absence of interphase before the first division
6) conjugation and crossing over of chromosomes
Answer
1. Establish the sequence of processes occurring during meiosis
1) arrangement of pairs of homologous chromosomes in the equatorial plane
2) conjugation, crossing over of homologous chromosomes
3) location in the equatorial plane and divergence of sister chromosomes
4) formation of four haploid nuclei
5) divergence of homologous chromosomes
Answer
2. Establish the sequence of processes of the first meiotic division. Write down the corresponding sequence of numbers.
1) chromosome conjugation
2) crossing over
3) arrangement of pairs (bivalents) of homologous chromosomes at the equator of the cell
4) divergence of homologous chromosomes, consisting of two chromatids, to opposite poles of the cell
5) spiralization of chromosomes with the formation of bivalents
6) formation of nuclei, division of the cytoplasm - the formation of two daughter cells
Answer
3. Establish the sequence of processes occurring in meiosis.
1) divergence of homologous chromosomes to the poles of the cell
2) divergence of sister chromosomes (chromatids) to the cell poles
3) gene exchange between homologous chromosomes
4) education four cells with a haploid set of chromosomes
5) conjugation of homologous chromosomes
Answer
4. Establish the sequence of meiotic processes. Write down the corresponding sequence of numbers.
1) arrangement of pairs of chromosomes along the equator of the cell
2) divergence of sister chromatids to opposite poles of the cell
3) conjugation and crossing over
4) formation of nuclei with a set of chromosomes and DNA nc
5) divergence of bichromatid chromosomes to opposite poles of the cell
Answer
5. Establish the sequence of processes occurring during meiotic division of an animal cell. Write down the corresponding sequence of numbers.
1) the formation of two cells with a haploid set of chromosomes
2) divergence of homologous chromosomes
3) conjugation with possible crossing over of homologous chromosomes
4) location in the equatorial plane and divergence of sister chromosomes
5) arrangement of pairs of homologous chromosomes in the equatorial plane of the cell
6) formation of four haploid nuclei
Answer
Look at the picture depicting cell division and determine A) the type of division, B) the set of chromosomes in the original cell, C) what specific cells are formed. Write down three numbers (numbers of terms from the proposed list) in the correct order.
1) mitosis
2) transcription
3) diploid
4) meiosis
5) direct
6) haploid
7) gamete
8) somatic
Answer
Choose one, the most correct option. Spores in flowering plants, unlike bacterial spores, are formed in the process
1) adaptation to life in unfavorable conditions
2) mitosis of haploid cells
3) meiosis of diploid cells
4) sexual reproduction
Answer
Choose one, the most correct option. DNA duplication and the formation of two chromatids during meiosis occurs in
1) prophase of the first meiotic division
2) prophase of the second division of meiosis
3) interphase before the first division
4) interphase before the second division
Answer
Look at the picture of cell division and determine (A) its phases, (B) the set of chromosomes in the daughter cells, and (C) what specific cells are formed as a result of such division in plants.
2) somatic
3) diploid
4) prophase 2, metaphase 2, anaphase 2, telophase 2
5) prophase 1, metaphase 1, anaphase 1, telophase 1
6) haploid
7) dispute
8) first meiotic division
Answer
Look at the picture depicting cell division and determine: A) what phases of division are depicted, B) the set of chromosomes of cells in each phase, C) what specific cells are formed in plants as a result of such division. Write down three numbers (numbers of terms from the proposed list) in the correct order.
1) prophase, metaphase, telophase
2) interphase
3) diploid
4) prophase 2, metaphase 2, anaphase 2
5) prophase 1, metaphase 1, anaphase 1
6) haploid
7) dispute
8) somatic
Answer
All of the characteristics listed below, except two, are used to describe the cell shown in the figure. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) homologous chromosomes are present
2) each chromosome contains one DNA molecule
3) the cell lacks a cell center
4) the formation of a mitotic spindle occurs
5) a metaphase plate has formed
Answer
All of the following characteristics, except two, can be used to describe the processes of the first meiotic division. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) formation of two haploid nuclei
2) divergence of single-chromatid chromosomes to opposite poles of the cell
3) formation of four cells with a set of nc
4) exchange of sections of homologous chromosomes
5) chromosome spiralization
Answer
Choose one, the most correct option. In the first division of meiosis,
1) polyploid cells
2) diploid cells
3) gametes
4) haploid cells
Answer
Choose one, the most correct option. During sexual reproduction, the maintenance of the constancy of the chromosome set in a series of generations of the species is ensured
1) recombination of genes in chromosomes
2) the formation of identical daughter cells
3) divergence of sister chromosomes
4) a decrease in the number of chromosomes in gametes
Answer
How does prophase of the first division of meiosis differ from prophase of mitosis? In response, write down the numbers of two correct options out of the five proposed.
1) the nuclear membrane disappears
2) chromosome spiralization occurs
3) chromosome conjugation occurs
4) chromosomes are arranged randomly
5) crossing over occurs
Answer
All but two of the characteristics listed below are used to describe the phase of meiosis shown in the figure. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) chromosome bivalents are located at the equator of the cell
2) homologous chromosomes, consisting of two chromatids, diverge to opposite poles
3) daughter chromatids diverge to opposite poles of the cell
4) there is a reduction in the number of chromosomes
5) chromosome set in the n2c cell at each cell pole
Answer
Look at the picture and determine (A) the type of division, (B) the phase of division, (C) the amount of genetic material in the cell. For each lettered cell, select the appropriate term from the list provided. Write down the selected numbers in the order corresponding to the letters.
1) anaphase II
2) n2c (at each cell pole)
3) metaphase
4) meiosis
5) 2n2c
6) mitosis
7) anaphase I
Answer
How many spermatozoa are formed as a result of spermatogenesis from one diploid primary germ cell? Write down only the corresponding number in your answer.
Answer
All but two of the following characteristics can be used to describe meiosis. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) two diploid cells are formed
2) four haploid cells are formed
3) one division occurs, consisting of four phases
4) two divisions occur, each of which consists of four phases
5) homologous chromosomes containing two chromatids diverge to the poles of the cell
Answer
All of the following characteristics, except two, can be used to describe the processes that occur in the prophase of the first meiotic division. Identify two characteristics that “drop out” from the general list, and write down the numbers under which they are indicated in your answer.
1) formation of two nuclei
2) divergence of homologous chromosomes
3) bringing together homologous chromosomes
4) exchange of sections of homologous chromosomes
5) chromosome spiralization
Answer
Select three features of mitotic cell division.
1) bichromatid chromosomes diverge to the poles
2) sister chromatids move towards the poles
3) double chromosomes appear in daughter cells
4) as a result, two diploid cells are formed
5) the process takes place in one division
6) as a result, haploid cells are formed
Answer
Select three differences between the first meiotic division and the second
1) pairs of homologous chromosomes are located at the equator of the cell
2) there is no telophase
3) conjugation and crossing over of chromosomes occurs
4) there is no conjugation and crossing over of chromosomes
5) sister chromatids diverge to the cell poles
6) homologous chromosomes diverge to the cell poles
Answer
What processes occur during meiosis?
1) transcription
2) reduction
3) denaturation
4) crossing over
5) conjugation
6) broadcast
Answer
The biological essence of meiosis is:
1) the emergence of a new nucleotide sequence;
2) the formation of cells with double the number of chromosomes;
3) formation of haploid cells;
4) recombination of sections of non-homologous chromosomes;
5) new combinations of genes;
6) the appearance of a larger number of somatic cells.
Answer
Choose three correct answers out of six and write down the numbers under which they are indicated. During the process of meiosis occurs
1) formation of germ cells
2) formation of prokaryotic cells
3) reducing the number of chromosomes by half
4) preservation of the diploid set of chromosomes
5) formation of two daughter cells
6) development of four haploid cells
Answer
Establish a correspondence between the characteristics and phases of cell division: 1) metaphase of mitosis, 2) anaphase of mitosis, 3) prophase I of meiosis. Write numbers 1-3 in the order corresponding to the letters.
A) exchange of chromosome sections
B) alignment of chromosomes along the equator of the cell
B) formation of the spindle
D) set of chromosomes and number of DNA molecules in a cell – 4n4c
D) division of chromosome centromeres
Answer
Establish a correspondence between the feature of the process and the phase of meiosis for which it is characteristic: 1) anaphase I, 2) anaphase II, 3) telophase II. Write numbers 1-3 in the order corresponding to the letters.
A) divergence of sister chromosomes to different poles of the cell
B) formation of four haploid nuclei
B) divergence of bichromatid chromosomes to opposite poles
D) doubling the number of chromosomes in a cell when sister chromatids diverge
D) independent divergence of chromosomes from each homologous pair
Answer
Establish a correspondence between the characteristics and phases of meiosis: 1) prophase of the first division, 2) anaphase of the second division. Write numbers 1 and 2 in the order corresponding to the letters.
A) conjugation of homologous chromosomes
B) formation of bivalents
B) chromatid separation
D) reduction of spindle microtubules
D) dissolution of the karyolemma
Answer
1) anaphase
2) metaphase
3) prophase
4) telophase
5) mitosis
6) meiosis I
7) meiosis II
Answer
Determine the phase and type of division shown in the figure. Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
1) anaphase
2) metaphase
3) prophase
4) telophase
5) mitosis
6) meiosis I
7) meiosis II
Answer
Determine the phase and type of division shown in the figure. Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
1) anaphase
2) metaphase
3) prophase
4) telophase
5) mitosis
6) meiosis I
7) meiosis II
Answer
Determine the phase and type of division shown in the figure. Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
1) anaphase
2) metaphase
3) prophase
4) telophase
5) mitosis
6) meiosis I
7) meiosis II
Answer
© D.V. Pozdnyakov, 2009-2019
1. How many daughter cells and with what set of chromosomes are formed from one diploid cell as a result of: a) mitosis; b) meiosis?
Two haploid, two diploid, four haploid, four diploid.
a) As a result of mitosis - two diploid cells.
b) As a result of meiosis, there are four haploid cells.
2. What is chromosome conjugation? In what phase of meiosis does crossing over occur? What is the significance of this process?
Chromosome conjugation is observed in prophase of meiosis I. This is the process of bringing together homologous chromosomes. During conjugation, the chromatids of homologous chromosomes intersect in some places. Crossing over also occurs in prophase of meiosis I and is an exchange of regions between homologous chromosomes. Crossing over leads to recombination of hereditary material and is one of the sources of combinative variability, due to which descendants are not exact copies of their parents and differ from each other.
3. What events occurring in meiosis ensure that the number of chromosomes in daughter cells is halved?
A decrease in the chromosome set occurs in anaphase I of meiosis due to the fact that not sister chromatids (as in anaphase of mitosis and anaphase II of meiosis), but bichromatid homologous chromosomes diverge to different poles of the dividing cell. Consequently, from each pair of homologous chromosomes only one will end up in the daughter cell. At the end of anaphase I, the set of chromosomes at each pole of the cell is already haploid (1n2c).
4. What's it like biological significance meiosis?
In animals and humans, meiosis leads to the formation of haploid germ cells - gametes. During the subsequent process of fertilization (fusion of gametes), the organism of the new generation receives a diploid set of chromosomes, which means it retains its inherent this species organisms karyotype. Therefore, meiosis prevents the number of chromosomes from increasing during sexual reproduction. Without such a division mechanism chromosome sets would double with each subsequent generation.
In plants, fungi and some protists, spores are formed through meiosis.
The processes occurring in meiosis (crossing over, independent divergence of chromosomes and chromatids) serve as the basis for the combinative variability of organisms.
5. Compare mitosis and meiosis, identify similarities and differences. What is the main difference between meiosis and mitosis?
The main difference is that as a result of meiosis, the set of chromosomes in daughter cells decreases by 2 times compared to the mother cell.
Similarities:
● They are methods of dividing eukaryotic cells and require energy.
● Accompanied by an accurate and uniform distribution of hereditary material between daughter cells.
● Similar processes of cell preparation for division (replication, doubling of centrioles, etc.).
● Similar processes occurring in the corresponding phases of division (spiralization of chromosomes, disintegration of the nuclear membrane, formation of the division spindle, etc.) and, as a consequence, the same names of the phases (prophase, metaphase, anaphase, telophase). The second division of meiosis proceeds by the same mechanism as mitosis of a haploid cell.
Differences:
● As a result of mitosis, daughter cells retain the set of chromosomes inherent in the mother cell. As a result of meiosis, the set of chromosomes in daughter cells decreases by 2 times.
● Mitosis is one cell division, and meiosis is two successive cell divisions (meiosis I and meiosis II). Therefore, as a result of mitosis, two daughter cells are formed from one mother cell, and as a result of meiosis, four are formed.
● Unlike mitosis, meiosis involves conjugation of homologous chromosomes and crossing over. Note: in fact, mitotic crossing over also exists (discovered by K. Stern in 1936), but its study is not included in the school curriculum.
● In anaphase of mitosis, sister chromatids diverge to different poles of the cell, and in anaphase I of meiosis, homologous chromosomes diverge.
And (or) other significant features.
6. A birch root cell contains 18 chromosomes.
1) The diploid cell of the birch anther has undergone meiosis. The resulting microspores divided by mitosis. How many cells were formed? How many chromosomes does each of them contain?
2) Determine the number of chromosomes and total chromatids in birch cells during meiotic division:
a) in the equatorial plane of the cell in metaphase I;
b) in metaphase II;
c) at each cell pole at the end of anaphase I;
d) at each cell pole at the end of anaphase II.
1) The birch root cell is somatic, which means that birch has 2n = 18. As a result of meiosis, 4 cells are formed from one mother cell with a halved set of chromosomes. Consequently, 4 haploid microspores (n = 9) were formed from the diploid anther cell.
Each microspore then divided by mitosis. As a result of mitosis, two daughter cells with the same set of chromosomes were formed from each microspore. Thus, a total of 8 haploid cells were formed.
Answer: 8 cells were formed, each containing 9 chromosomes.
2) The formula of the hereditary material located in the equatorial plane of the cell in metaphase I is 2n4c, which for birch is 18 chromosomes, 36 chromatids. A cell in metaphase II has a set of 1n2c - 9 chromosomes, 18 chromatids. At the end of anaphase I, at each pole of the cell there is a set of 1n2c - 9 chromosomes, 18 chromatids, and at the end of anaphase II - 1n1c - 9 chromosomes, 9 chromatids.
Answer: a) 18 chromosomes, 36 chromatids; b) 9 chromosomes, 18 chromatids; c) 9 chromosomes, 18 chromatids; d) 9 chromosomes, 9 chromatids.
7. Why is meiosis not observed in organisms that do not have sexual reproduction?
In the development cycle of all organisms that are characterized by sexual reproduction, the process of fertilization takes place - the fusion of two cells (gametes) into one (zygote). In fact, fertilization doubles the chromosome number. Therefore, there must also be a mechanism that reduces the number of chromosomes by 2 times, and this mechanism is meiosis. Without meiosis, chromosome sets would double with each successive generation.
Organisms that do not reproduce sexually do not undergo fertilization. Therefore, they do not have meiosis, there is no need for it.
8. Why is the second division of meiosis necessary, since a decrease in the number of chromosomes by 2 times has already occurred as a result of the first division?
Daughter cells formed as a result of the first meiotic division have a set of 1n2c, i.e. are already haploid. However, each chromosome of such a cell does not consist of one chromatid, as it should be in a young cell entering a new cell cycle, and of the two - as in a mature cell, ready to divide. Consequently, cells with the 1n2c set will not be able to normally go through the cell cycle (and, above all, replication in the S period). Therefore, almost immediately after the first meiotic division, the second begins, during which sister chromatids diverge with the formation of “normal” single-chromatid chromosomes, characteristic of young daughter cells.
In addition, as a result of meiosis, gametes are formed in animals and humans, and spores are formed in plants. Due to the fact that meiosis is not one, but two successive divisions, the number of gametes (or spores) formed increases by 2 times.
Catalog of tasks.
Cell life cycle/mitosis/meiosis
Return to task catalog
Version for printing and copying in MS Word
For each division feature animal cell determine whether it is characteristic of mitosis (1) or meiosis (2):
| A | B | IN | G | D | E |
Explanation.
Only in meiosis there are two divisions; in prophase, crossing over occurs and gametes with a single set of chromosomes are formed.
Answer: 122121.
Anastasia Lonchakova (Komsomolsk-on-Amur) 01.03.2013 01:42
Only in meiosis there are 2 divisions; in prophase, crossing over occurs and gametes with a single set of chromosomes are formed.
Your answer: 122112. Correct answer: 122121
Isn't crossing over in meiosis1?
Natalia Evgenievna Bashtannik
The explanation says that in meiosis there are 2 (two in number) divisions. Conjugation, crossing over and exchange of homologous regions occur in the first division of meiosis.
The question asks to distribute between mitosis - number 1 and meiosis - number 2, and not between the first and second meiotic divisions.
Daniil Efanov 19.03.2019 23:06
in meiosis, conjugation will necessarily occur, but crossing over is not at all necessary. therefore "E" is suitable for both answer options
Anatoly Stepura
Daniil, “crossing over does not necessarily occur” and “crossing over does not occur” are formulations with different meanings. "Crossing over does not occur" - this means " at all there is no crossing over."
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
Explanation.
Under the letters B, D, D - mitosis - indirect cell division, the most common method of reproduction of eukaryotic cells. The biological significance of mitosis is the strictly identical distribution of chromosomes between daughter nuclei, which ensures the formation of genetically identical daughter cells and maintains continuity in a number of cell generations.
Under the letters A, B, E - meiosis, or reduction cell division - division of the nucleus of a eukaryotic cell with a halving of the number of chromosomes.
Answer: 212112.
Guest 28.05.2013 15:40
Why does meiosis maintain a constant number of chromosomes if the explanation says: “division of the nucleus of a eukaryotic cell with a halving of the number of chromosomes.”?
Natalia Evgenievna Bashtannik
maintains the constancy of chromosomes over generations... during meiosis, the set of chromosomes is halved, and after fertilization it is restored
Malikova Anastasia 22.10.2016 15:07
According to the reference book N.V. Chebysheva, G.S. Guzikova, Yu.B. Lazarev and S.N. Larina mitosis ensures the constancy of the chromosome set over a number of cell generations, and meiosis prevents the doubling of the number of chromosomes in each new generation.
Natalia Evgenievna Bashtannik
Mitosis "in a series of cell generations" ...
I do not justify the writers of the assignment :(
but in the wording as it is presented in the assignment it is not indicated that we're talking about about one cell, they talk about generations... that’s why meiosis is suggested in the answers
Establish a correspondence between the features of cell division and its type.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
Explanation.
Under the letters B, C - mitosis - indirect cell division, the most common method of reproduction of eukaryotic cells. The biological significance of mitosis is the strictly identical distribution of chromosomes between daughter nuclei, which ensures the formation of genetically identical daughter cells and maintains continuity in a number of cell generations.
Under the letters A, D, D, E - meiosis, or reduction cell division - division of the nucleus of a eukaryotic cell with a halving of the number of chromosomes.
Answer: 211222.
Answer: 211222
Establish a correspondence between the type of cell and the method of its formation.
| A | B | IN | G | D | E |
Explanation.
Method of formation: mitosis: moss sperm, sunflower egg, fern archegonium cell. Method of formation: meiosis: moss spores, monkey sperm, poppy microspores. Spores in plants are formed by meiosis, and gametes by mitosis. In animals, gametes are formed by meiosis.
Answer: 212121.
Answer: 212121
Natalia Evgenievna Bashtannik
At the top male plants moss contains the genital organs, in which motile germ cells (gametes) develop - spermatozoa(from Greek words"sperm" - seed, "zoon" - living creature and "eidos" - species).
Microspore poppy (from micro... and spore) - haploid cells of heterosporous higher plants, formed in microsporangia as a result of meiotic division of maternal (archesporial) cells. In seed plants they are transformed into pollen grains; in spore plants, during germination they give rise to the male gametophyte.
Establish a correspondence between the events occurring with cell nuclei in mitosis and meiosis.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
Explanation.
Mitosis under the letters: B) formation of diploid cells; B) in anaphase, single-chromatid daughter chromosomes are formed at the cell poles; D) the content of genetic material does not change. Meiosis I under the letters: A) formation of bivalents; D) crossing over occurs; E) in anaphase, bichromatid chromosomes diverge to the poles of the cell.
Answer: 211212.
Answer: 211212
Establish a correspondence between the processes occurring during cell division and the methods of division. For each position given in the first column, select the corresponding position from the second column.
| A | B | IN | G | D | E |
Explanation.
Mitosis under the letters: A) ensures the growth and development of the organism; B) as a result of division they are formed
somatic cells; D) is the basis of vegetative propagation. Meiosis under the letters: B) maintains the constancy of the number of chromosomes in the cells of individuals of the same species during sexual reproduction; D) underlies combinative variability; E) bivalents are formed during fission.
Answer: 112212.
Answer: 112212
Establish a correspondence between the processes occurring at different stages of the cell life cycle: for each position given in the first column, select the corresponding position from the second column.
Write down the selected numbers in the table under the corresponding letters
| A | B | IN | G | D | E |
Explanation.
Interphase under the letters: A) intensive metabolism; C) doubling the number of organelles; E) DNA replication. Mitosis under the letters: B) spiralization of chromosomes; D) formation of a fission spindle; D) arrangement of chromosomes along the equator of the cell.
Answer: 121221.
Alexandra Mokina 13.03.2018 06:14
The doubling of the number of organelles occurs in cytokinesis, which occurs in parallel with the telophase of mitosis in general case. Therefore, the correct answer is: 122221
Anatoly Stepura
Cytokinesis is the process of cytoplasmic division, during which the formation of organelles does not occur. Cell growth and an increase in the number of all organelles occur in interphase.
Establish a correspondence between the processes occurring at different stages of the cell life cycle and the stages in which these processes occur: for each position given in the first column, select the corresponding position from the second column.
Write down the selected numbers in the table under the corresponding letters
| A | B | IN | G | D | E |
Explanation.
Interphase under the letters: A) DNA replication; B) assembly of ribosomes; D) duplication of centrioles. Mitosis under the letters: B) formation of the spindle; D) chromatid divergence to the poles; E) disappearance of the nuclear membrane.
Answer: 121212.
Note.
Interphase is the period between two cell divisions, the time from the last division until the cell dies or loses the ability to divide. During this period, the cell grows and doubles its DNA, as well as mitochondria and plastids. In interphase, protein and other organic compounds are synthesized. The synthesis process occurs most intensively in the synthetic period of interphase. At this time, nuclear chromatids are doubled, energy is accumulated that will be used during division. The number of cellular organelles and centrioles also increases.
Answer: 121212
Natalia Evgenievna Bashtannik
Centrioles double during the synthetic period of interphase.
Establish a correspondence between the processes and phases of mitosis shown in the figures: for each position given in the first column, select the corresponding position from the second column.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
Explanation.
1) prophase: A) divergence of centrioles to the poles of the cell; D) chromosome spiralization;
2) metaphase: B) attachment of spindle filaments to chromosomes; D) alignment of chromosomes in one plane (at the equator);
3) anaphase: B) shortening of the spindle filaments; E) movement of chromosomes to the poles of the cell.
Note.
During mitosis, chromosomes are compacted, and a special apparatus is formed, which is responsible for uniform distribution hereditary information between cells that are formed as a result of this process.
The phases of mitosis are characterized by the following features:
prophase - the nuclear membrane disappears. In this phase, centrioles diverge to the poles of the cell, spindle filaments are formed, and chromosomes condense (compact);
metaphase - characterized by the placement of maximally compacted chromosomes, which consist of two chromatids, at the equator (in the middle) of the cell. This phenomenon is called the metaphase plate. It is during this period that chromosomes can be clearly seen under a microscope. In the metaphase of mitosis, some ends of the spindle filaments are also attached to the centromeres of the chromosomes, and other ends to the centrioles;
anaphase - during this period, the chromosomes are divided into chromatids (they diverge to different poles). In this case, the chromatids become separate chromosomes, which consist of only one chromatid strand;
telophase - characterized by the decondensation of chromosomes and the formation of a new nuclear envelope around each chromosome. The filaments of the spindle disappear, and nucleoli appear in the nucleus.
Answer: 132213.
Establish a correspondence between the characteristics of mitosis and its phases: for each position given in the first column, select the corresponding position from the second column.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
Explanation.
1) anaphase: B) set of chromosomes and number of DNA molecules in the cell - 4n4c; D) separation of chromatids at the centromere
2) prophase: A) chromosome spiralization; B) disappearance of the nucleolus; D) destruction of the nuclear membrane; E) divergence of centrioles towards the poles
Answer: 221212
Note.
During mitosis, chromosomes are compacted, and a special apparatus is formed, which is responsible for the uniform distribution of hereditary information between the cells that are formed as a result of this process.
The phases of mitosis are characterized by the following features:
prophase - the nuclear membrane disappears. In this phase, centrioles diverge to the poles of the cell, spindle filaments are formed, and chromosomes condense (compact);
metaphase - characterized by the placement of maximally compacted chromosomes, which consist of two chromatids, at the equator (in the middle) of the cell. This phenomenon is called the metaphase plate. It is during this period that chromosomes can be clearly seen under a microscope. In the metaphase of mitosis, some ends of the spindle filaments are also attached to the centromeres of the chromosomes, and other ends to the centrioles;
anaphase - during this period, the chromosomes are divided into chromatids (they diverge to different poles). In this case, the chromatids become separate chromosomes, which consist of only one chromatid strand;
telophase - characterized by the decondensation of chromosomes and the formation of a new nuclear envelope around each chromosome. The filaments of the spindle disappear, and nucleoli appear in the nucleus.
Answer: 221212
Section: Reproduction and individual development of organisms
Establish a correspondence between the processes and stages of mitosis: for each position given in the first column, select the corresponding position from the second column.
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
Explanation.
1. Prophase: A) DNA compaction; D) disappearance of the nuclear membrane; E) formation of the fission spindle.
2. Metaphase: B) alignment of chromosomes along the equator.
3. Anaphase: B) divergence of chromatids to the poles of the cell; D) shortening of the spindle filaments.
Answer: 123131.
Note.
During mitosis, chromosomes are compacted, and a special apparatus is formed, which is responsible for the uniform distribution of hereditary information between the cells that are formed as a result of this process.
The phases of mitosis are characterized by the following features:
Prophase - the nuclear membrane disappears. In this phase, centrioles diverge to the poles of the cell, spindle filaments are formed, and chromosomes condense (compact);
Metaphase - characterized by the placement of maximally compacted chromosomes, which consist of two chromatids, at the equator (in the middle) of the cell. This phenomenon is called the metaphase plate. It is during this period that chromosomes can be clearly seen under a microscope. In the metaphase of mitosis, some ends of the spindle filaments are also attached to the centromeres of the chromosomes, and other ends to the centrioles;
A) compaction of chromosomes
B) divergence of chromosomes to the poles
B) chromosomes contain one chromatid
D) exchange of sections between chromosomes
E) a set of chromosomes and DNA molecules - 2n2c
E) formation of bivalents
1) prophase I
2) anaphase II
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D | E |
Explanation.
Correspondence between characteristics and stages of meiosis:
A) divergence of monochromatid chromosomes
B) shortening of the spindle filaments
B) conjugation of homologous chromosomes
D) disappearance of the nuclear membrane
D) formation of the spindle
1) prophase I of meiosis
2) anaphase II of meiosis
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
Write down the numbers in your answer, arranging them in the order corresponding to the letters:
| A | B | IN | G | D |
Explanation.
Correspondence between characteristics and stages of the cell cycle:
1) metaphase of mitosis: B) chromosomes line up along the equator of the cell; E) spindle filaments are attached to the centromeres of chromosomes;
2) interphase: A) chromosome doubling; B) formation of new organelles; D) chromosomes in an untwisted state.
Answer: 22121.
Answer: 22121
Take tests on these tasks
1. How many daughter cells and with what set of chromosomes are formed from one diploid cell as a result of: a) mitosis; b) meiosis?
During mitosis, 2 daughter cells with a diploid set of chromosomes are formed. As a result of meiosis, 4 haploid cells are formed.
2. What is chromosome conjugation? In what phase of meiosis does crossing over occur? What is the significance of this process?
Conjugation is the process of bringing homologous chromosomes together. During conjugation, the chromatids of homologous chromosomes intersect in some places. Between some chromatids of homologous chromosomes, an exchange of corresponding sections can occur - crossing over. Crossing over occurs in prophase I and prophase I of meiosis.
3. What events occurring in meiosis ensure that the number of chromosomes in daughter cells is halved?
In anaphase I, homologous chromosomes (and not sister chromatids, as in mitosis) move away from each other and are stretched by spindle filaments to opposite poles of the cell. Consequently, from each pair of homologous chromosomes, only one will end up in the daughter cell. Thus, at the end of anaphase I, the set of chromosomes and chromatids at each pole of the dividing cell is 1n2c - it has already been halved.
4. What is the biological significance of meiosis?
In animals and humans, meiosis leads to the formation of haploid germ cells - gametes. During the subsequent process of fertilization (fusion of gametes), the organism of the new generation receives a diploid set of chromosomes, which means it retains the karyotype inherent to this type of organism. Therefore, meiosis prevents the number of chromosomes from increasing during sexual reproduction. Without such a division mechanism, chromosome sets would double with each subsequent generation. In plants, fungi and some protists, spores are formed by meiosis. The processes occurring during meiosis serve as the basis for the combinative variability of organisms.
5. Compare mitosis and meiosis, identify similarities and differences. What is the main difference between meiosis and mitosis?
After mitosis, somatic cells (body cells) are obtained, and after meiosis, germ cells are obtained (gametes - sperm and eggs; in plants, after meiosis, spores are obtained). After mitosis, the number of chromosomes in daughter cells remains the same as it was in the mother cell, and after meiosis it decreases by 2 times (the number of chromosomes is reduced).
6. A birch root cell contains 18 chromosomes. 1) The birch anther diploid cell has undergone meiosis. The resulting microspores divided by mitosis. How many cells were formed? How many chromosomes does each of them contain? 2) Determine the number of chromosomes and the total number of chromatids in birch cells during meiotic division: a) in the equatorial plane of the cell in metaphase I; b) in metaphase II; c) at each cell pole at the end of anaphase I; d) at each cell pole at the end of anaphase II.
1) As a result of division of the anther cell, 8 cells were formed and each had 9 chromosomes.
2) a) metaphase I – 2n4c = 18 chromosomes 36 chromatids b) metaphase II – 1n2c = 9 chromosomes 18 chromatids c) anaphase I – 1n2c = 9 chromosomes 18 chromatids d) anaphase II – 1n1c = 9 chromosomes 9 chromatids
7. Why is meiosis not observed in organisms that do not have sexual reproduction?
Haploid cells participate in sexual reproduction. If an organism is not characterized by sexual reproduction, then they do not need meiosis, which results in the formation of haploid cells.
8. Why is the second division of meiosis necessary, since a decrease in the number of chromosomes by 2 times has already occurred as a result of the first division?
Thanks to the second division of meiosis, haploid cells (sex cells - gametes) are formed. As a result of their further fusion, an organism is formed with a diploid set of chromosomes, which means that the karyotype inherent to this type of organism is preserved. The second division prevents the number of chromosomes from increasing.