Question

Описать мейотическое деление( по фазам), отличие митоза от мейоза, биологическое значение митоза и мейоза.

Answer 1

Митотический цикл клетки
1.Интерфаза:
G1-подготовка(подготовка к синтезу ДНК,усиленно образуется РНК и белки,повышается активность ферментов
S-синтез(редупликация ДНК или ее удвоение)
G2-подготовка2(подготовкак митозу,синтез белков,удвоение центриолей,завершение роста клетки
МИТОЗ
1.Профаза-спиралезуются хромосомы,центриоли расходятся к полюсам,формируются нити веретена деления(диплоидный набор хромосом)
2.Метофаза-хромосомы выстраиваются по экватору,нити веретена деления прикрепляются к центромерам хромосом.
3.Анафаза-нити веретена деления сокращаются,хроматиды расходятся к разным полюсам
4.Телофаза-нити веретена деления исчезают,хромосомы диспиралезуются,формируется ядро,центромера делится на 2 части,формируются 2 дочерние клетки.
В результате митоза происходит точное распределение генетической информацией между дочерними клетками.
1 клетка-диплоидный набор,после чего формируются две дочерние клтки с таким же диплоидным набором 2n.
В результате МЕЙОЗА из одной дочерней клетки с диплоидным набором хромосом 2n образуются 4 клетки с гаплоидным набором 1n хромосом.Так же в МЕЙОЗЕ в отличие от митоза происходят двойной деление за счет Коньюгации и Кроссирговера

Answer 2

Meiotic Division and Phases

Meiotic division is a type of cell division that occurs in sexually reproducing organisms. It involves the formation of gametes (sperm and eggs) with half the number of chromosomes as the parent cell. Meiosis consists of two successive divisions, known as meiosis I and meiosis II. Each division is further divided into several phases.

Meiosis I: 1. Prophase I: This is the longest phase of meiosis and can be further divided into five subphases: leptotene, zygotene, pachytene, diplotene, and diakinesis. During prophase I, homologous chromosomes pair up and undergo genetic recombination through a process called crossing over. 2. Metaphase I: Homologous chromosome pairs align at the equatorial plate of the cell. 3. Anaphase I: Homologous chromosomes separate and move towards opposite poles of the cell. 4. Telophase I: Chromosomes reach the poles of the cell, and the cytoplasm divides, resulting in two daughter cells.

Meiosis II: 1. Prophase II: Chromosomes condense, and the nuclear envelope breaks down. 2. Metaphase II: Chromosomes align at the equatorial plate of the cell. 3. Anaphase II: Sister chromatids separate and move towards opposite poles of the cell. 4. Telophase II: Chromosomes reach the poles of the cell, and the cytoplasm divides, resulting in the formation of four haploid daughter cells.

Difference between Mitosis and Meiosis

Mitosis and meiosis are both types of cell division, but they have distinct differences:

1. Number of Divisions: Mitosis consists of one division, resulting in the formation of two identical daughter cells. Meiosis consists of two divisions, resulting in the formation of four genetically diverse daughter cells. 2. Chromosome Number: Mitosis produces daughter cells with the same number of chromosomes as the parent cell (diploid). Meiosis reduces the chromosome number by half, producing haploid daughter cells. 3. Genetic Variation: Mitosis does not involve genetic recombination, so the daughter cells are genetically identical to the parent cell. Meiosis involves crossing over and independent assortment, leading to genetic variation among the daughter cells. 4. Purpose: Mitosis is involved in growth, repair, and asexual reproduction. Meiosis is specifically for the production of gametes and sexual reproduction.

Biological Significance of Mitosis and Meiosis

Mitosis: - Growth and Development: Mitosis plays a crucial role in the growth and development of multicellular organisms. It allows for the production of new cells to replace damaged or old cells. - Tissue Repair: Mitosis enables the regeneration of tissues and the healing of wounds by replacing damaged cells. - Asexual Reproduction: Some organisms, such as bacteria and plants, reproduce asexually through mitosis, allowing for the rapid production of genetically identical offspring.

Meiosis: - Production of Gametes: Meiosis is responsible for the formation of gametes (sperm and eggs) in sexually reproducing organisms. It ensures that the offspring receive a combination of genetic material from both parents, leading to genetic diversity. - Genetic Variation: Meiosis introduces genetic variation through processes like crossing over and independent assortment. This variation is essential for the survival