They have a haploid set of chromosomes. Chromosome: concept, diploid and haploid chromosome sets

Have you ever thought about why a born and grown up child looks like his parents in appearance and habits? “Genetics is like that,” you might say. And many people know that parents and children have similar DNA. This is what the chromosomes contain. "What else is this?" - Nine out of ten people who encounter this concept will exclaim in bewilderment. There are several layouts. Today we will look at the haploid and diploid set of chromosomes. But let's first understand what it is.

Concept definition

The chromosome is a nucleoprotein structure, one of the components of the nucleus of a eukaryotic cell. It stores, implements and transmits hereditary information. Chromosomes can only be distinguished with a microscope at the time when mitotic or meiotic cell division occurs. The karyotype, as the totality of all the chromosomes of a cell is called, is a species-specific trait with a relatively low level individual variability. These DNA-containing structures in eukaryotic organisms are found in the mitochondria, nucleus, and plastids. In prokaryotes - in cells without a nucleus. And the chromosomes of viruses is a DNA or RNA molecule located in the capsid.

History of the concept

According to the most common version, chromosomes were discovered in 1882 by the German anatomist Walter Fleming. Although "discovered" is a loud word, he only collected and organized all the information about them. In 1888, the German histologist Heinrich Waldeyer first proposed calling the new structures chromosomes. It is difficult to answer when and by whom the first descriptions and drawings were made. A couple of years after Mendel's laws were discovered, it was suggested that chromosomes play an important role. genetic role. Chromosomal theory was confirmed in 1915 by the founders of classical genetics. They were G. Möller, K. Bridges, A. Sturtevant and T. Morgan. The last in 1933 was received Nobel Prize in the field of physiology and medicine for the fact that he substantiated the role of chromosomes in heredity.

Ploidy

The total number of identical chromosomes indicates their ploidy. There are haploid, polyploid and diploid sets of chromosomes. Now we will talk about the first and third.

Haploid set of chromosomes

Let's start with haploid. It is a cluster of completely different chromosomes, i.e. in a haploid organism there are several of these nucleoprotein structures that are unlike each other (photo). The haploid set of chromosomes is characteristic of plants, algae and fungi.

Diploid set of chromosomes

This set is such a collection of chromosomes, in which each of them has a double, i.e. these nucleoprotein structures are arranged in pairs (photo). The diploid set of chromosomes is characteristic of all animals, including humans. By the way, about the last one. At healthy person there are 46 of them, i.e. 23 couples. However, his sex is determined by only two, called sex, - X and Y. Their location is determined even in the womb. If the scheme of such chromosomes is XX, a girl will be born, but if they are arranged in the form of XY, a boy will be born. However, ploidy disturbances can also be observed, leading to negative changes in the physical and mental state organisms such as:

These diseases are genetic in nature and are incurable. Children and adults with one of these or many similar chromosomal syndromes lead dysfunctional lives, and some do not survive to adulthood at all.

Conclusion

See how important chromosomes are to all organisms. At various kinds animals and plants have a different number and number of sets of these nucleoprotein structures.

Concept definition

The chromosome is a nucleoprotein structure, one of the components of the nucleus of a eukaryotic cell. It stores, implements and transmits hereditary information. Chromosomes can only be distinguished with a microscope at the time when mitotic or meiotic cell division occurs. The karyotype, as the totality of all chromosomes of a cell is called, is a species-specific trait with a relatively low level of individual variability. These DNA-containing structures in eukaryotic organisms are found in the mitochondria, nucleus, and plastids. In prokaryotes - in cells without a nucleus. And the chromosomes of viruses is a DNA or RNA molecule located in the capsid.

History of the concept

According to the most common version, chromosomes were discovered in 1882 by the German anatomist Walter Fleming. Although "discovered" is a loud word, he only collected and organized all the information about them. In 1888, the German histologist Heinrich Waldeyer first proposed calling the new structures chromosomes. It is difficult to answer when and by whom the first descriptions and drawings were made. A couple of years after Mendel's laws were discovered, it was suggested that chromosomes play an important genetic role. The chromosome theory was confirmed in 1915 by the founders of classical genetics. They were G. Möller, K. Bridges, A. Sturtevant and T. Morgan. The last in 1933 received the Nobel Prize in Physiology or Medicine for the fact that he substantiated the role of chromosomes in heredity.

Ploidy

The total number of identical chromosomes indicates their ploidy. There are haploid, polyploid and diploid sets of chromosomes. Now we will talk about the first and third.

Haploid set of chromosomes

Diploid set of chromosomes

This set is such a collection of chromosomes, in which each of them has a double, i.e. these nucleoprotein structures are arranged in pairs (photo). The diploid set of chromosomes is characteristic of all animals, including humans. By the way, about the last one. A healthy person has 46 of them, i.e. 23 couples. However, his sex is determined by only two, called sex, - X and Y. Their location is determined even in the womb. If the scheme of such chromosomes is XX, a girl will be born, but if they are arranged in the form of XY, a boy will be born. However, ploidy disorders can also be observed, leading to negative changes in the physical and mental state of the body, such as:

Conclusion

See how important chromosomes are to all organisms. Different species of animals and plants have a different number and number of sets of these nucleoprotein structures.

) a set of chromosomes inherent in a mature germ cell, in which only one of each pair of chromosomes characteristic of a given biological species is present; in a person G. n. X. represented by 22 autosomes and one sex chromosome.

Big Medical Dictionary. 2000 .

See what the "haploid set of chromosomes" is in other dictionaries:

Haploid set of chromosomes- a set of chromosomes in gametes, which is equal to half of the diploid set of somatic cells ... Source: METHODOLOGICAL RECOMMENDATIONS PREDICTION, EARLY PRECLINICAL DIAGNOSIS AND PREVENTION OF INSULIN-DEPENDENT DIABETES MELLITUS (N 15) (approved ... ... Official terminology

haploid set of chromosomes- haploidinis chromosomų rinkinys statusas T sritis augalininkystė apibrėžtis Chromosomų rinkinys, į kurį ląstelių branduolyje įeina po vieną chromosomą iš kiekvienos homologinių chromosomų poros. atitikmenys: engl. haploid chromosome set rus.… … Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

HAPLOID SET OF CHROMOSOMES- the main (or initial) number of chromosomes observed after reduction division in the cells of the plant gametophyte ... Glossary of botanical terms

HAPLOID SET- Normal number of chromosomes in each gamege (sex cell: egg and sperm) a certain kind. Haploid set (which = 23 y Homo sapiens) is half the diploid set, the number of chromosomes in each somatic cell ... Dictionary in psychology

haploid set- (Greek gaploos single, eidos species) the normal number of chromosomes in each gamete (in humans - 23, until recently it was believed that there were 24 of them). Somatic cells contain twice the number of chromosomes, a diploid set (46 chromosomes). Other's… … encyclopedic Dictionary in psychology and pedagogy

Big Medical Dictionary

See Haploid set of chromosomes... Big Medical Dictionary

haploid- Characterizes an individual (cell) that has one set of chromosomes (n); normally haploid are gametes, gametophytes and males of some species with haploidy diploidy; haploid individuals can be formed as a result of induced ... ... Technical Translator's Handbook

Haploid haploid. Characterizes an individual (cell) that has one set of chromosomes (n); normally haploid are gametes, gametophytes and males of some species with haploidy diploidy ; Individuals can be haploid Molecular biology and genetics. Dictionary.

Haploid- (gr. single species) a single set of chromosomes of germ cells, constituting half of the diploid set of somatic cells ... Concepts modern natural science. Glossary of basic terms

Chromosomal sets of somatic cells of male and female individuals of each species differ in one pair of chromosomes. This pair is the sex chromosomes, or heterochromosomes. All other pairs of chromosomes that are the same in both sexes have common name- autosomes.

For example, in the human karyotype, pairs of chromosomes that are the same for women and men are autosomes. One pair - the twenty-third - in men and women determines the sex. Therefore, the chromosomes that make up it are called sex chromosomes. This pair in women is homologous (XX), and in men it is heterologous (XY). That is why sex chromosomes are also called heterosomes (from "hetero" - different).

Chromosome Rules

1. The rule of constancy of the number of chromosomes. The number of chromosomes in a cell is constant in every species. That is, the number of chromosomes and characteristics their structures are a species feature. For example, in humans - 46, chimpanzees - 48, fruit flies - 8 chromosomes ( general formula-2a).

2. The rule of chromosome pairing. Chromosomes in a diploid set form pairs. Those chromosomes that belong to the same pair are called homologous. These chromosomes are similar in size, shape, location of centromeres, and the set of genes they contain. In each pair, one chromosome is from the mother, the other is from the father.

3. The rule of individuality. Chromosomes of different pairs differ from each other: in size; form; the location of the constrictions; by striation, revealed by special coloring - DOC (differential staining of chromosomes); according to the set of genes they contain. The set of genes of one pair is no longer repeated in any other pair.

4. The rule of chromosome continuity. Each new generation has the same structure and shape of chromosomes as the previous one, i.e., chromosomes from generation to generation retain a relatively constant shape and structure. This is possible because DNA is capable of reduplication (self-doubling).

Thus, one more definition of a karyotype can be given: a karyotype is a set of chromosomes of a somatic cell, which is characterized by a constant number of chromosomes for the species, their size, shape and location of centromeres in them.

The only way the formation of new cells is the division of previous cells.

The life or cell cycle is the time from the appearance of a cell to its death or the formation of new cells from it, that is, it is its ontogeny.

The mitotic cycle is the life of a cell from the moment of its appearance to the end of its division with the formation of two new cells. (This is one of the variants of the cell cycle).

There are cells that life cycle coincides with the mitotic cycle. These are cells that are constantly dividing. For example, cells of the skin epidermis, testicles (renewable cell complexes). There are cells that do not have a mitotic cycle (stable cell complexes). These cells lose their ability to divide (eg erythrocytes, neurons). But it has been shown that such a state can be reversible. For example, if the nucleus is removed from the egg of a frog and the nucleus is transplanted there nerve cell, it starts to divide. Based on this, we can conclude that the cytoplasm of the egg contains substances that activate mitosis.

Described three ways of dividing eukaryotic cells:

Amitosis (direct division);

Mitosis (indirect division);

Meiosis (reduction division).

Amitosis is a division in which the interphase nucleus divides by constriction. There is no condensation of chromosomes. Sometimes, after nuclear fission, the cytoplasm does not divide and binuclear cells are formed. Amitosis described in cells skeletal muscles, cells of the skin epithelium, as well as in pathologically altered cells (tumor cells).

Mitosis is a division in which two cells with a diploid set of chromosomes are formed from one cell with a diploid set of chromosomes. This method of division is universal for eukaryotic cells. It underlies the asexual reproduction of organisms. Mitosis is the growth of tissues and the whole organism.

Mitosis is part of the mitotic cycle. The entire mitotic cycle consists of interphase (preparation of the cell for division) + mitosis (the actual division).

Interphase has three periods:

1. Presynthetic - in 1

2. Synthetic - B

3. Postsynthetic - 0 2

Presynthetic period - the cell grows, accumulates ATP, RNA, proteins necessary for the formation of cellular organelles. During this period, the cell acquires features characteristic of this tissue. In this period, the cell has 2n, 2s (n is the haploid set of chromosomes, c is the amount of DNA in one chromatid): i.e., a double set of single chromatid chromosomes.

Synthetic period - DNA reduplication occurs, RNA continues to be synthesized, histone proteins are synthesized. At the end of this period, the cell has 2n,4c: _ i.e., a double set of two-chromatid chromosomes. (The number of chromosomes does not change, but each chromosome already consists of two chromatids).

Postsynthetic period - RNA, proteins necessary for the fission process, ATP, mitochondrial DNA are synthesized. The number of mitochondria, plastids, and centrioles doubles. In this period, the cell has 2p, 4s.,

In interphase, the nucleus is rounded, with clear boundaries. One or more nucleoli are visible in it, Chromosomes - in the form of chromatin, are located in the karyoplasm.

Mitosis is divided into four main phases:

1. prophase;

2. metaphase;

3.anaphase;

4.telophase.

Prophase. The nucleus is markedly enlarged. The nucleoli are removed. Happens. spiralization (condensation, or stacking) of chromosomes: at the beginning of prophase they are thin and long, at the end they are thick and short. Centrioles diverge towards the poles of the cell, the spindle of division begins to form. At the end of prophase, each chromosome is seen to consist of 2 chromatids. Prophase is considered complete when the nuclear envelope breaks up into fragments and the chromosomes enter the cytoplasm. In this period, the cell has 2p, 4s. Each chromosome has two chromatids.

Prometaphase can also be distinguished between prophase and metaphase when chromosomes move towards the equator.

Metaphase. Chromosomes are located at the equator of the cell. A fission spindle thread is attached to each cromatid in the region of the centromere. The chromatids of each chromosome remain connected only in the region of the centromere. In this period, the cell has 2n, 4c (a diploid set of two-chromatid chromosomes).

Anaphase. The chromatids of each chromosome separate from each other at the centromere. The spindle fibers contract and stretch the chromatids (now called daughter chromosomes) to different poles of the cell. In this period, the cell has 4p, 4c (a tetraploid set of single chromatid chromosomes).

Rice. Phases of mitosis

Telophase. At the beginning of the phase, despiralization (unwinding) of chromosomes occurs. A nuclear envelope forms around each cluster of chromosomes. Nucleoli appear. The nuclei take the form of interphase nuclei. The spindle of division gradually disappears. At the end of telophase, cytokinesis occurs, or cytotomy (dividing the cytoplasm of the mother cell). Two daughter cells are formed from one mother cell. They enter the interphase state. In this period, each new cell has 2p, 2c (a double set of single chromatid chromosomes). That is, starting from the anaphase and up to the S-period of the interphase, each chromosome consists of one chromatid.

biological significance mitosis

1. Preservation of a constant number of chromosomes in daughter cells (each new cell has the same set of chromosomes as the original - 2p).

2. Uniform distribution of hereditary information between daughter cells.

3. Growth of a new organism at asexual reproduction through the production of new body cells.

4. Regeneration (recovery) of lost cells and organs.

Meiosis is a process consisting of two successive divisions. From one cell with a diploid set of chromosomes (2n, 4c), four haploid cells (n, c) are formed. That is, during meiosis, a reduction (decrease) in the number of chromosomes occurs in the cell.

In each of the divisions of meiosis, the same phases are distinguished as in mitosis: prophase (I and II), metaphase (I and II), anaphase (I and II) and telophase (I and II). But the duration of the individual phases and the processes occurring in them differ significantly from mitosis. The main differences are:

1. Prophase I is the longest. Therefore, it is divided into five stages:

Leptotena: chromosomes begin to spiral;

Zygotene: Homologous chromosomes are conjugated (tightly adjacent to each other along the entire length). Such pairs are called bivalents;

Pachytene: conjugation is complete. Between conjugating chromosomes, an exchange of homologous regions (containing the same genes) can occur - crossing over (or recombination). The sites of exchange are called chiasmata;

Diplotene: repulsive forces arise between homologous chromosomes, first in the centromere region, and then in other areas. It becomes noticeable that these figures consist of four elements. That is, bivalents turn into tetrads. Chromatids in tetrads are linked in the region of telomeres and chiasms;

Diakinesis: chromosomes are maximally spiralized, bivalents are isolated and placed along the periphery of the nucleus. Tetrads shorten, nucleoli disappear.

Meiosis resembles mitosis, but has its own characteristics:

a) In the prophase of the first meiosis, in contrast to mitosis, the conjugation of homologous chromosomes occurs. Between homologous chromosomes there is an exchange of homologous regions, genes (crossing over).

o) In metaphase I, at the equator of the cell, there are homologous chromosomes connected in pairs (one opposite the other) (Fig. 34, metaphase I).

c) During anaphase, it is not chromatids that diverge to the poles (as during mitosis), but two-chromatid homologues (Fig. 34, anaphase I). Therefore, after the first meiotic division, the daughter cells (oocyte II and one polar body during oogenesis and spermatocytes II during spermatogenesis) have a haploid set of chromosomes, but each chromosome consists of two chromatids.

d) Interphase II is very short, because DNA replication is not needed (chromosomes are two-chromatid).

The remaining phases of meiosis II pass quite quickly, not differing from mitotic division. In anaphase, paired sister chromatids separate one by one into daughter cells. Thus, during meiosis, four cells are formed from one original cell (2n, 4c), each with a haploid set of single-chromatid chromosomes (n, s).

The biological significance of meiosis

1. During meiosis, a haploid set of chromosomes is formed in new cells. And during fertilization (fusion of gametes), the diploid set of chromosomes is restored. Thus, in all organisms, the constancy of the number of chromosomes from generation to generation is preserved.

2. During time of two divisions of meiosis, recombination occurs

genetic material due to

a) crossing over;

b) independent divergence of paternal and maternal chromosomes. Combinative variability arises - this provides a variety of material for evolution.

3FEATURES OF THE STRUCTURE OF SEX CELLS (GAMETS)

The eggs are immobile, usually spherical in shape. They contain all the cellular organelles characteristic of somatic cells. But the eggs contain substances (for example, the yolk) necessary for the development of the embryo. Based on the amount of yolk, the eggs are divided into different types. For example, an isolecithal egg: there is little yolk in it and it is evenly distributed throughout the cytoplasm (the egg of a lancelet, a person). Reptiles and birds have a lot of yolk (telolecithal egg) and it is located at one of the poles of the cell. This pole is called vegetative (nourishing). The opposite pole, where there is little yolk, carries the cell nucleus and is called animal. The type of crushing of the zygote depends on the amount and distribution of the yolk.

The largest egg is in sharks (50 - 70 mm in diameter), in chickens - more than 30 mm (without protein coats), in cows - 100 microns, in humans - 130-200 microns.

The eggs are covered with membranes that perform protective and other functions (for example, in placental mammals - for the embryo to grow into the wall of the uterus).

Spermatozoa are small cells (in humans, they have a length of 50-70 microns) and consist of a head, neck and tail. The head contains the nucleus and a small amount of cytoplasm. The acrosome is located at the anterior end of the head. This is a modified Golgi complex. It contains enzymes that break down egg shells during fertilization. The neck contains mitochondria and centrioles. One centriole is proximal (near), it, together with the head, penetrates the egg. The other is distal (far), a tail is attached to it. The mitochondria of the neck provide it with energy. The tail contains microtubules.

Features of germ cells:

They have a haploid set of chromosomes.

In germ cells, compared with somatic cells, less intensive metabolism is noted. The egg cells accumulate substances necessary for the development of the embryo.

Spermatozoa never divide, and the egg, after the introduction of the sperm into it, separates the secondary polocyte (i.e., only now the second division of meiosis is completed in it).

In biology, the term "ploidy" is used to refer to the number of sets contained in a . At different organisms different number of chromosomes. Two types of cells are also diploid cells, the main difference of which is the number of sets of chromosomes in their nuclei.

Diploid cells are cells with two sets of chromosomes. In diploid organisms, each parent passes on one set of chromosomes, which combine into two sets in the offspring. Most mammals are diploid organisms, meaning that there are two homologous copies of each chromosome in the cells. Humans have 46 chromosomes. most diploid organisms, with the exception of (a) are diploid and contain two sets of chromosomes.

Diploid cells divide with the help of which a completely identical copy of the cell is formed. In humans, somatic cells (or non-sex cells) are all diploid cells. These include the cells that make up organs, muscles, bones, skin, hair, and any other part of the body other than eggs (in women) or sperm (in men).

diploid number

The diploid number of a cell is the number of chromosomes in the nucleus of the cell. This number is usually denoted as 2n, where n is equal to the number of chromosomes. For a person, this equation has next view 2n=46 . Humans have 2 sets of 23 chromosomes, for a total of 46 chromosomes:

Non-sex chromosomes: 22 pairs of autosomes.

Sex chromosomes: 1 pair of gonosomes.

The difference between haploid and diploid cells

The main difference between haploid and diploid cells is the number of sets of chromosomes contained in the nucleus. Ploidy is a biological term that characterizes the number of chromosomes in a cell. Therefore, cells with two sets are diploid, and cells with one set are haploid.

In diploid organisms such as humans, haploid cells are only used for reproduction, while the rest of the cells are diploid. Another difference between haploid and diploid cells is how they divide. haploid cells reproduce with help, while diploid cells go through mitosis.