Question

3. Explain the importance of the reduction division, crossing over and independent assortment Introduction Write a short paragraph complaining the purpose of Mclosis and contrast it with the purpose of Mitosis. Then give the ways in which the chromosomal movements in Melosis and Mitosis are similar, and the ways h which they are different button store locomo Mno Understanding the Reduction Division. Draw the products of the each of the two divisions below (do not worry about independent assortment or crossing over yet, you will focus on those in the next simulations). Toitubonjol Parental Nucleus Pay close attention to the differences between artesanos DND SOM GEOSYN Snipriaislaxare 3575 Tonle E SA homologous chromosomes and si exterovom lemogororlog iniw dla swart vindt tristanit sent inwas sister chromatids, and the differences between how the chromosomes separate in oo000 Meiosis I and Meiosis II. 00 000 0000000 oooo After Meiosis ! After Meiosis II

Answer 1

3) Importance of reduction division

Meiosis is a reduction division that is necessary in sexually reproducing organisms to maintain the species number of chromosomes. Gametes, or sex cells must have half the chromosomes that the parent cell has. At fertilization, two gametes fuse together to form the offspring. If these gametes had the same number of chromosomes as the parent does, each generation would have double the chromosomes as the previous generation did. To prevent that, meiosis occurs in the gonads--ovaries or testes. If the ovary or teste cell is diploid(2n), the gametes or sex cells--sperm and eggs will be haploid(n)after meiosis occurs. For example, if a human teste or ovary cell has 46 chromosomes, replication occurs. The result will be 46 pairs or 92 chromosomes. Meiosis has two rounds of cell division--meiosis I and II. After meiosis I takes place, two daughter cells, each with 46 chromosomes are the result. After meiosis II occurs, each of these daughter cells divides and four haploid cells are the result. In this example, they will each have 23 chromosomes or the haploid amount. These can be used as gametes--sperm or egg cells during sexual reproduction. In the case of males, all four haploid cells will develop into sperm. In the case of females, only one becomes the ova or egg cell, and the other three are called polar bodies.

Importance of crossing over

Chromosomal crossover, or crossing over, is the exchange of genetic material during sexual reproduction between two homologous chromosome's non-sister chromatids that results in recombinant chromosomes. It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosisduring a process called synapsis. Synapsis begins before the synaptonemal complexdevelops and is not completed until near the end of prophase I. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome. Crossing over is essential for the normal segregation of chromosomes during meiosis.Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical.

Importance of independent assortment

The Law of Independent Assortment speaks of alleles of a geneseparating independently from alleles of another gene. Hence, the inheritance pattern of one trait will not affect the inheritance pattern of another. For instance, the gene for the eye color is inherited independently from the gene for hair color. That is, not all individuals with brown eyes will always have a black hair color; others may still have a different hair color. It is because the gene coding for the eye color separates independently (and randomly) from the gene coding for the hair color during formation of gametes (meiosis).
Independent assortment of genes is important to produce new genetic combinations that increase genetic variations within a population.