The term genome refers to the diploid set of chromosomes. Homologous chromosomes, diploid set of chromosomes. Diploid set of chromosomes
Children inherit from their parents not only material property, but also certain genes that make them look like relatives in the shape of their head, face, hands, eye and hair color, and sometimes even character.
The transmission of traits from parents to children occurs with the help of information encoded in deoxyribonucleic acid (DNA). All biological information is stored in chromosomes, which are DNA molecules covered with a histone (protein) shell. Depending on the type of cell and its phase of the life cycle, genetic information in the form of chromosomes can be found in several variants: haploid, diploid, and, less commonly, tetraploid.
The concept of a chromosome
The nucleus of a eukaryotic cell contains several types of components, one of which is a nucleoprotein structure called a chromosome. The theory of hereditary information was first put forward in the 19th century, but, based on actual data, it was fully formed only a century later.
With the help of DNA storage, implementation and transmission of hereditary information. Chromosomes can only be distinguished under a microscope during cell division. The totality of all structural and functional units contained in a cell is called a karyotype.
Nucleoprotein structures, storing hereditary information, in eukaryotes are located in the nucleus, as well as in mitochondria and plastids; in prokaryotes, the DNA molecule closed in a ring is located in the so-called nucleoid zone. In viruses, the only ones of their kind, the role of a carrier of genetic information can be performed by both DNA and RNA (ribonucleic acid) located in protein shells - capsids.
Usually, the genetic information in a cell is contained in a single copy, this state is called a haploid set. When a cell divides, the DNA is replicated, that is, doubled, so that each young cell receives a complete genetic set. This state of chromosomes is called diploid. Less commonly, during the formation of germ cells (eggs and spermatozoa), during the formation of spores and conidia in the life cycles of lower plants and fungi, as well as in case of genetic abnormalities, a quadruple set of genetic information can be found in the cell - tetraploid.
The diploid set of chromosomes is double karyotype, in which the elements are divided into pairs according to similar features. Such a set is observed in somatic cells and zygotes.
Human cells contain 46 chromosomes, which are divided into 23 pairs with their "double" in length and thickness. But the 45th and 46th units differ from others in that they are sex chromosomes, a certain combination of which affects the sex of the future person:
- a pair of identical units - XX - will lead to the birth of a female child;
- two different units - XY - to the birth of a boy.
The remaining structures are called autosomes.
The haploid chromosome set is a single set of structural and functional units that differ from each other in size. Haploid karyotypes contain 22 autosomes and 1 sex structure. Plants, algae, and fungi have nuclei with a single element set.
Diploid and haploid karyotypes can exist at the same time. This phenomenon is observed during sexual processes. During this period, the phases of the haploid and diploid sets alternate: with the division of the complete set, a single karyotype is formed, and then a pair of single sets merges, which are converted into a diploid karyotype.
Possible abnormalities in the karyotype
During the period of development at the cell level, failures and disturbances in the functioning of chromosomes are possible. With changes in chromosome sets, a person develops genetic diseases. Known diseases with abnormal karyotype are:
- Down syndrome. The disease is characterized by a failure in the 21st pair of structural and functional units, which are adjacent to exactly the same additional chromosome. The homologous element is redundant and results in an anomaly called a trisomy. With a violation of the 21st pair of the diploid set, the fetus may lag behind in development and die. If a child is born, then a violation in the cells will lead to a reduction in the future life of the baby. In mental development, he will lag behind. Unfortunately, this syndrome is incurable.
- Shereshevsky-Turner syndrome. With this disease, one of the reproductive structures in the 23rd pair of the karyotype is missing. People with this syndrome have characteristic anomalies in physical development, short stature and sexual infantilism.
- Edwards syndrome. Trisomy of the 18th chromosome, formed before fertilization, leads to a chromosomal disease characterized by a set of malformations.
- Patau Syndrome. A severe congenital disease is characterized by a number of body deformities that occur due to the appearance of an additional 13th chromosome in the cells. Usually, babies with this syndrome live only a few weeks, but there have been cases when children born with an incurable defect lived for several years.
- Klinefelter syndrome. The hereditary disease observed in the male sex can manifest itself in polysomy in different ways, but most often the second X element is attached to the XY pair, resulting in the formation of the XXY scheme. The presence of an anomaly in the chromosome set leads to disorders in the reproductive system and mental development, as well as to systemic diseases of the human body.
Since scientists have not yet found ways to protect cells from abnormalities in karyotypes, chromosomal changes lead to incurable diseases in which there is a low degree of viability, mental and sexual development abnormalities, and growth retardation.
With the help of numerous studies, scientists have found that changes in chromosome sets are affected by the influence of ecology, poor heredity, lack of sleep and an unhealthy lifestyle. But violations can also occur in people who lead an absolutely correct lifestyle and do not suffer from any diseases. At the moment, people cannot influence changes in karyotypes.
Video
This video compilation will help you better understand what a human chromosome set is.
Chromosomes are dense, intensely staining structures that are units of the morphological organization of the genetic material and ensure its precise distribution during cell division. The number of chromosomes in the cells of each biological species is constant. Usually in the nuclei of body cells (somatic) chromosomes are presented in pairs, in germ cells they are not paired. Vasilyeva V.I., Volkov I.M., Yarygin V.N., Sinelshchikova V.V. Biology. 2 book. Book. 1. M: Higher School, 2004. - 76-78s.
A single set of chromosomes in germ cells is called haploid (n), a set of chromosomes in somatic cells is called diploid (2n). The chromosomes of different organisms differ in size and shape. A diploid set of chromosomes in cells of a particular type of living organisms, characterized by the number, size and shape of chromosomes, is called a karyotype. In the chromosome set of somatic cells, paired chromosomes are called homologous, chromosomes from different pairs are called non-homologous. Homologous chromosomes are the same in size, shape, composition (one is inherited from the maternal, the other from the paternal organism). The chromosomes in the karyotype are also divided into autosomes, or non-sex chromosomes, which are the same in male and female individuals, and heterochromosomes, or sex chromosomes involved in sex determination and differing in males and females. The human karyotype is represented by 46 chromosomes (23 pairs): 44 autosomes and 2 sex chromosomes (the female has two identical X chromosomes, the male has X and Y chromosomes).
During sexual reproduction, the genomes of two parental germ cells combine to form the genotype of a new organism. All somatic cells of such an organism have a double set of genes received from both parents in the form of certain alleles. Thus, the genotype is the genetic constitution of the organism, which is the totality of all the hereditary inclinations of its cells, contained in their chromosome set - the karyotype.
Karyotypes of organisms of various species are shown in Figure 1.
Rice. one. Karyotypes of organisms of various species: I - skerds, II - Drosophila. III - human
Karyotype - a diploid set of chromosomes, characteristic of the somatic cells of organisms of a given species, which is a species-specific feature and is characterized by a certain number, structure and genetic composition of chromosomes (Fig. 3.67). Below are the numbers of chromosomes of somatic cells of some types of organisms.
If the number of chromosomes in the haploid set of germ cells is denoted by n, then the general karyotype formula will look like 2n, where the value of n is different in different species. Being a species characteristic of organisms, the karyotype may differ in individual individuals by some particular features. For example, representatives of different sexes have basically the same pairs of chromosomes (autosomes), but their karyotypes differ in one pair of chromosomes (heterochromosomes, or sex chromosomes). Sometimes these differences consist in a different number of heterochromosomes in females and males (XX or XO). More often, the differences relate to the structure of the sex chromosomes, denoted by different letters - X and Y (XX or XY). Vasilyeva V.I., Volkov I.M., Yarygin V.N., Sinelshchikova V.V. Biology. 2 book. Book. 1. M: Higher school, 2004. - 112 p.
Each type of chromosome in the karyotype containing a certain complex of genes is represented by two homologues inherited from parents with their germ cells. A double set of genes enclosed in a karyotype - a genotype - is a unique combination of paired alleles of the genome. The genotype contains the development program of a particular individual. - a complete haploid set of genes or chromosomes of a cell or organism.
(sex cells) are haploid cells formed by division through meiosis.
haploid number
The haploid number is the number of chromosomes in the nucleus, which makes up one set of chromosomes. This number is usually denoted as n, where n equals the number of chromosomes. For different organisms, the haploid number will be different. In humans, the haploid number is expressed as n=23.
Human haploid cells have 1 set of 23 chromosomes:
- Non-sex chromosomes: 22 autosomes.
- Sex chromosomes: 1 gonosome.
Human diploid cells contain 23 pairs or 46 chromosomes:
- Non-sex chromosomes: 22 pairs, consisting of 44 autosomes.
- Sex chromosomes: 1 pair, including 2 gonosomes.
Haploid cell reproduction
Haploid cells are produced during meiosis. In meiosis, it divides twice to form four haploid daughter cells. Before the start of the meiotic cycle, the cell replicates its DNA, increases its mass and quantity in a stage known as interphase.
When a cell divides through meiosis, it goes through two stages (meiosis I and meiosis II) of prophase, metaphase, anaphase, and telophase. At the end of meiosis I, the cell divides into two. separated, yet stay together. The cells then enter meiosis II and divide again.
At the end of meiosis II, sister chromatids separate each of the four cells with half the number of chromosomes relative to the parent (original) cell. In the process of sexual reproduction, haploid cells unite at fertilization and become diploid cells.
In organisms such as plants, algae and fungi, asexual reproduction is accomplished by the production of haploid spores.
These organisms have life cycles that can alternate between haploid and diploid phases. This type of life cycle is known as . In plants and algae, haploid to gametophyte structures without fertilization.
The gametophyte produces gametes and is considered the haploid phase in the life cycle. The diploid phase of the cycle consists in the formation of sporophytes. Sporophytes are diploid structures that develop from fertilized germ cells.
Chromosomes are located in the nucleus of the cell, they are the main components of the nucleus.
The chemical composition of chromosomes is 50% DNA and 50% protein.
The function of chromosomes is the storage of hereditary information.
A chromosome can be single (from one chromatids) and double (of two chromatids). Centromere(primary constriction) is the junction of two chromatids.
- A single chromosome becomes a double chromosome in the process of DNA doubling (replication, reduplication) in interphase.
- A double chromosome turns into two single ones (chromatids become daughter chromosomes) after the separation of the centromere connecting them (in anaphase of mitosis and anaphase II of meiosis).
Chromosome sets
The set of chromosomes can be:
- single (haploid, n), in humans 23
- double (diploid, 2n), in humans 46
- triple (triploid, 3n)
- quadruple (tetraploid, 4n), etc.
The haploid set is characteristic of gametes (sex cells, spermatozoa and eggs), as well as spores. The diploid set is characteristic of somatic cells (cells of the body).
- The haploid set turns into a diploid one during fertilization (two haploid gametes merge, a diploid zygote is obtained).
- The diploid set turns into haploid in the first division (an independent divergence of homologous chromosomes occurs, the number of chromosomes is halved).
The triploid set of chromosomes is characteristic of the endosperm of the seeds of flowering plants. In double fertilization, the following merge:
- haploid sperm and egg; a diploid zygote is obtained, from which an embryo is formed;
- haploid sperm and diploid central cell of the embryo sac; resulting in triploid endosperm.
Solving problems on the number of chromosomes:
1) You need to understand where given number of chromosomes:
- if in a gamete, then the number given in the problem is n
- if in a somatic cell, then 2n
- if in the endosperm, then 3n
2) Math-time, calculate n
- if 2n=24 then n=24/2=12
- if 3n=24 then n=24/3=8
3) Math-two: if n=24, then
- there will be n=24 in the gamete
- in a somatic cell will be 2n=2x24=48
- endosperm will have 3n=3x24=72
You can also try to understand
37 related tests
Choose one, the most correct option. Daughter chromatids become chromosomes after
1) separation of the centromere connecting them
2) alignment of chromosomes in the equatorial plane of the cell
3) exchange of sites between homologous chromosomes
4) pairing of homologous chromatids
Answer
Choose one, the most correct option. What set of chromosomes will the cells have after the first division of meiosis if the mother cell contained 12 chromosomes?
1) 6
2) 12
3) 3
4) 24
Answer
Choose one, the most correct option. A tetraploid organism produces gametes
1) haploid
2) diploid
3) triploid
4) tetraploid
Answer
Choose one, the most correct option. Consists of one nucleic acid molecule in combination with proteins
1) chloroplast
2) chromosome
3) gene
4) mitochondrion
Answer
Choose one, the most correct option. Storage tissue (endosperm) in flowering plants has a set of chromosomes
1) n
2) 2n
3) Zn
4) 4n
Answer
Choose one, the most correct option. The restoration of the diploid set of chromosomes in the zygote occurs as a result of
1) meiosis
2) mitosis
3) fertilization
4) conjugations
Answer
All of the features listed below, except for two, are used to describe the cellular structure depicted in the figure. Identify two signs that “fall out” from the general list, and write down the numbers under which they are indicated.
1) always have the shape of the letter "X"
2) are made up of DNA and proteins
3) when dividing, they are compact and clearly visible under a microscope
4) doubling occurs in interphase
5) when dividing, they are in the nucleus
Answer
Establish a correspondence between eukaryotic cells and sets of chromosomes in them: 1) haploid, 2) diploid. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) moss spores
B) pine sperm
B) frog leukocyte
D) human neuron
D) horsetail zygote
E) bee egg
Answer
SOMATIC - ENDOSPERM
1. There are 34 chromosomes in the karyotype of an apple tree. How many chromosomes will be contained in the cells of the endosperm of her seed? Write down the correct number for your answer.
Answer
2. The diploid set of corn is 20 chromosomes. What set of chromosomes do maize endosperm cells have? Write down only the number of chromosomes in your answer.
Answer
3. There are 14 chromosomes in rye leaf cells. What set of chromosomes does a rye endosperm cell have? Write down only the number of chromosomes in your answer.
Answer
4. There are 16 chromosomes in an onion leaf cell. What set of chromosomes do endosperm cells of onion seed have? Write down only the number of chromosomes in your answer.
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ENDOSPERM - SOMATIC
1. A cherry endosperm cell contains 24 chromosomes. What set of chromosomes does a leaf cell have? Write down only the number of chromosomes in your answer.
Answer
2. There are 36 chromosomes in lily seed endosperm cells. What set of chromosomes does a lily leaf cell have? Write down only the number of chromosomes in your answer.
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GAMETE - ENDOSPERM
1. There are 10 chromosomes in the sperm of a flowering plant. How many chromosomes do the endosperm cells of this plant contain? Write down only the number of chromosomes in your answer.
Answer
2. How many chromosomes does the endosperm cell of the seed of a flowering plant contain if there are 7 chromosomes in the sperm of this plant? Write down only the appropriate number in your answer.
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ENDOSPERM - GAMETE
There are 30 chromosomes in a corn seed endosperm cell. What set of chromosomes does a corn egg have? In response, write down only the number of chromosomes.
Answer
GAMETE - SOMATIC (PLANTS)
1. The set of chromosomes in maize sperm is 10. What set of chromosomes does the somatic cells of this organism have? Write down only the number of chromosomes in your answer.
Answer
2. How many chromosomes are in cucumber leaf cells if there are 7 chromosomes in cucumber sperm? Write down the correct number for your answer.
Answer
GAMETE - SOMATIC (ANIMAL)
1. There are 19 chromosomes in a domestic cat's egg, how many chromosomes are in her brain cell? In response, write down only the number of chromosomes.
Answer
2. A fish sperm contains 28 chromosomes. What set of chromosomes does a fish somatic cell have? Write down only the number of chromosomes in your answer.
Answer
3. The set of chromosomes of a pea egg cell is 7. What set of chromosomes do the somatic cells of this organism have? Write down only the number of chromosomes in your answer.
Answer
4. The set of chromosomes of potato germ cells is 24. What set of chromosomes does the somatic cells of this organism have? Write down only the number of chromosomes in your answer.
Answer
5. There are 48 chromosomes in a hedgehog egg. What set of chromosomes does a hedgehog skin cell have? Write down only the number of chromosomes in your answer.
Answer
6. How many chromosomes does a somatic cell of an animal have if gametes contain 38 chromosomes? Write down only the appropriate number in your answer.
Answer
SOMATIC - GAMETE (PLANTS)
1. A wheat somatic cell contains 28 chromosomes. What set of chromosomes does her sperm have? Write down only the number of chromosomes in your answer.
Answer
2. There are 14 chromosomes in the somatic cells of barley. How many chromosomes are in barley sperm. In response, write down only the number of chromosomes.
Answer
3. How many chromosomes does the gooseberry sperm nucleus have if the leaf cell nucleus contains 16 chromosomes. Write down the correct number for your answer.
Answer
SOMATIC - GAMETE (ANIMAL)
1. There are 38 chromosomes in a somatic cell of a cat. What set of chromosomes does the egg of this organism have? Write down only the number of chromosomes in your answer.
Answer
2. There are 34 chromosomes in the somatic cell of the fox. What set of chromosomes does the spermatozoon of this organism have? Write down only the number of chromosomes in your answer.
Answer
3. There are 56 chromosomes in the somatic cell of the fish body. What set of chromosomes does a fish spermatozoon have? Write down only the number of chromosomes in your answer.
Answer
4. There are 78 chromosomes in the somatic cell of a wolf. What set of chromosomes does the sex cells of this organism have? Write down only the number of chromosomes in your answer.
Answer
SOMATIC - SOMATIC
Strawberry stem cells have 14 chromosomes. What set of chromosomes does a strawberry embryo cell have? Write down only the number of chromosomes in your answer.
Answer
SOMATIC - ZYGOTE
1. The diploid set of a cockroach is 48 chromosomes. What set of chromosomes does a cockroach zygote have? Write down only the number of chromosomes in your answer.
Answer
2. There are 20 chromosomes in the nuclei of the cells of the intestinal mucosa of a vertebrate animal. What number of chromosomes will the nucleus of the zygote of this animal have? Write down the correct number for your answer.
Answer
3. The nucleus of a somatic cell of the human body normally contains 46 chromosomes. How many chromosomes are in a fertilized egg? Write down the correct number for your answer.
Answer
ZYGOTE - SOMATIC
1. How many chromosomes are contained in the nucleus of a skin cell if the nucleus of a fertilized human egg contains 46 chromosomes? Write down the correct number for your answer.
Answer
The mass of all DNA molecules in 46 chromosomes of one human somatic cell is about 6x10 -9 mg. What is the mass of all DNA molecules in a spermatozoon? In your answer, write down only the corresponding number without x10 -9.
Answer
SOMATIC - AFTER MEIOSIS
How many chromosomes are in the cell nucleus after meiosis if the diploid set contains 80 chromosomes? Write down only the appropriate number in your answer.
