Question

объясните, почему набор хромосом в клетках, образованных мейозом, изменяется. сколько дочерних клеток образуется?​

Answer 1

Мейоз - процесс деления половых клеток (гамет), вследствие чего получается 4 дочерние клетки.

Для примера можно взять сперматогенез, из сперматоцита 1 порядка (набор хромосом - 2n4c) получаются сперматоциты 2 порядка (набор хромосом - 1n2c), а из них - сперматоизоиды (1n1c)

Изменение набора хромосом от диплоидного 2n4с к гаплоидному 1n1c происходит для того, чтобы «на выходе» получалось большое количество различных и непохожих друг на друга генотипов. (Значение генотипа будет одинаково для всех дочерних клеток - 1n1c, но сами хромосомы будут отличаться, поэтому различные сочетания хромосом будут приводить к возникновению разных и непохожих признаков)

Чтобы понять этот процесс, нужно досконально изучить такие понятия, как меойз и митоз (+ и их фазы)

Удачи!

Answer 2

Explanation of Chromosome Changes in Cells Formed by Meiosis

During meiosis, the process of cell division that produces gametes (sperm and eggs), the arrangement of chromosomes in the resulting cells undergoes changes. This is important for genetic diversity and the formation of haploid cells. Let's explore why the chromosome set changes and how many daughter cells are formed.

Chromosome Set Changes: 1. Crossing Over: One of the key events in meiosis is crossing over, which occurs during prophase I of meiosis I. Homologous chromosomes exchange genetic material, resulting in the recombination of genes between the chromosomes. This process increases genetic diversity by creating new combinations of alleles on the chromosomes. 2. Independent Assortment: During metaphase I of meiosis I, homologous pairs of chromosomes align randomly at the cell's equator. This random alignment leads to the independent assortment of chromosomes, meaning that each pair of chromosomes can segregate independently of other pairs. As a result, the combination of chromosomes in the daughter cells is different from the parent cell. 3. Reduction Division: Meiosis consists of two rounds of cell division: meiosis I and meiosis II. Meiosis I is a reduction division, where the chromosome number is halved. Homologous chromosomes separate, resulting in two haploid cells with a single set of chromosomes. Each chromosome still consists of two sister chromatids joined by a centromere. 4. Equational Division: Meiosis II is an equational division, similar to mitosis. The sister chromatids of each chromosome separate, resulting in four haploid daughter cells, each with a single set of chromosomes.

Number of Daughter Cells Formed: During meiosis, four daughter cells are formed. These daughter cells are haploid, meaning they contain half the number of chromosomes compared to the parent cell. In humans, for example, the parent cell (a diploid cell) contains 46 chromosomes, while each daughter cell (haploid) contains 23 chromosomes.

In summary, the chromosome set changes in cells formed by meiosis due to crossing over, independent assortment, and the reduction and equational divisions of meiosis. These processes contribute to genetic diversity and the formation of haploid daughter cells. Meiosis results in the formation of four haploid daughter cells.