Please only help if you will be detailed. I\'m so lost and vague answers are not
ID: 302921 • Letter: P
Question
Please only help if you will be detailed. I'm so lost and vague answers are not helpful. If you could be detailed/help explain, I would appreciate it a lot. Thank you.
QUESTION #3 [10 pts] Mitosis and meiosis are both processes of cell division involved in reproduction. The following questions compare and contrast meiosis with mitosis. (For Parts A D only) a) The ploidy of daughter cells as a result of meiosis is different than that of the parental cell. Briefly explain what this statement means. Specify what phase during meiosis this change occurs. [2 pts] b) Just as in mitosis, cohesin is an important protein that keeps chromatids together during meiosis and is similarly targeted by separase as well. In the context of meiosis, however, there are multiple variants of cohesin with different qatnry structures. Why do you think this is necessary? [2 pts] c) Homologous recombination is a unique feature of meiosis whose purpose is to increase genetic diversity during reproduction. What does the process of homologous recombination entail, and how does this process achieve the purpose of increasing diversity? When does homologous recombination occur? [2 pts] d) Define independent assortment within the framework of meiosis. What impact does homologous recombination have on the principle of independent assortment? [3 pts]Explanation / Answer
a) In genetics, ploidy means the number of chromosomes occurring in the nucleus of a cell. In normal somatic cells, the chromosomes exist in pairs and is called diploidy. During meiosis the cell produces gametes, or germ cells, each containing half the normal or somatic number of chromosomes. Meiosis produces 4 haploid cells whereas Mitosis produces 2 diploid cells. The old name for meiosis was reduction/ division. Meiosis I reduces the ploidy level from 2n to n (reduction) while Meiosis II divides the remaining set of chromosomes in a mitosis-like process (division).
Occurs only in gametocyte stages of the germ cells. In meiosis, two cell divisions result in 4 new cells. Each of the 4 new cells receives only one chromosome of each original pair of chromosomes present in the primary gametocyte. Each of the 4 new cells contains a haploid number (n) of chromosomes and haploid (n) genetic content.
b) Cohesion is needed so that homologous targets can be found for repair of these breaks (either at sister chromatids during mitosis or at homologous chromosomes in meiosis).Cohesin is a protein complex that regulates the separation of sister chromatids during cell division, either mitosis or meiosis. Cohesins hold sister chromatids together after DNA replication until anaphase when removal of cohesin leads to separation of sister chromatids.
Homologues of the cohesin subunits have been identified in a variety of eukaryotic organisms from yeast to humans. Higher eukaryotes have three homologues of Scc3 termed SA1, SA2, and SA3, also known as STAG1, STAG2, and STAG3. SA1/STAG1 and SA2/STAG2 are present in mitosis while SA3/STAG3 is specific to meiosis. Both SA1 and SA2 associate with the other cohesin subunits to create a diverse group of cohesin complexes in vertebrates. Two mammalian homologues of Smc1 are termed SMC1?, found in both mitosis and meiosis, and SMC1?, which is specific to meiosis.
c) General recombination is also called as homologous recombination, allows large sections of the DNA double helix to move from one chromosome to another, and it is responsible for the crossing-over of chromosomes that occurs during meiosis in fungi, animals, and plants.
Recombination is an integral part of the pairing of homologous chromosomes. It occurs between non-sister chromatids during the pachytene stage of meiosis I (the first stage of meiosis) and possibly before, when the homologous chromosomes are aligned in zygotene.
Genetic variability is produced by genetic recombination through the process of crossing over when the chromosomes pair during meiotic prophase. Parental homologous chromosomes exchange segments during crossing over to produce recombinant chromosomes. It is most widely used by cells to accurately repair harmful breaks that occur on both strands of DNA, known as double-strand breaks. Accurate DNA replication and repair of DNA damage are essential to maintaining genetic information and ensuring its accurate transmission from parent to offspring. From the standpoint of evolution, however, it is also important to generate genetic diversity. The combination of the genes on the genome may change due to such DNA rearrangements. In a population, this sort of genetic variation is important to allow organisms to evolve in response to a changing environment.
d) The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop. During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes is random.
Principle of segregation is the generalization that a sexually reproducing organism has two "determinants" or genes for each characteristic, and these two copies segregate (or separate) during the production of gametes. Independent Assortment occurs in metaphase I. Segregation occurs in anaphase I. The principles of genetic inheritance are based on unique features of meiosis. Synapsis of homologous chromosomes and the separation of the homologous pairs during anaphase I cause the segregation of alleles. Crossing over and the random separation of chromosomes cause independent assortment.