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Chapter 2: Problem 14

Explain why meiosis leads to significant genetic variation while mitosis does not.

Short Answer

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Answer: Meiosis leads to significant genetic variation due to two important processes: crossing over and independent assortment of chromosomes, resulting in new combinations of genes and diverse sets of maternal and paternal chromosomes in the haploid cells. In contrast, mitosis creates genetically identical daughter cells with minor variation due to mutations. Therefore, meiosis is responsible for significant genetic variation, while mitosis is not.

Step by step solution

01

Meiosis Overview

Meiosis is a type of cell division that occurs in sexually reproducing organisms, in which one diploid (paired chromosome) cell divides into four haploid (single chromosome) cells. These haploid cells go on to form sex cells (gametes) like sperm and egg cells. One main characteristic of meiosis is that it introduces genetic variation through two significant events: crossing over and independent assortment.
02

Mitosis Overview

Mitosis, on the other hand, is a type of cell division that occurs in all organisms (both asexual and sexual). During mitosis, a single cell divides into two identical diploid cells, having the same number of chromosomes as the parent cell. Mitosis is mainly for growth, repair, and replacement of cells in an organism.
03

Crossing Over

Crossing over occurs during the prophase I of meiosis. Homologous chromosomes (pairs of matching chromosomes) come together and exchange genetic material by swapping equivalent sections of their DNA. This creates new combinations of genes in each chromosome, leading to genetic variation in the resulting haploid cells.
04

Independent Assortment

Independent assortment occurs during the metaphase I of meiosis. The homologous chromosomes align randomly along the center of the cell in a process called metaphase plate formation. This random alignment means that during the following anaphase I, the maternal and paternal chromosomes can be sorted randomly into the daughter cells. Consequently, there are many different combinations of maternal and paternal chromosomes (2^n, where n is the number of chromosome pairs) that can be passed on to the haploid cells - another source of genetic variation in meiosis.
05

Mitosis and Genetic Variation

In mitosis, there is no crossing over or independent assortment of chromosomes during the single cell division. Thus, the two resulting daughter cells are genetically identical copies of the parent cell. However, minor genetic variation may arise during mitosis due to mutations, but it is significantly lesser than that produced during meiosis.
06

Conclusion

Meiosis leads to significant genetic variation due to two important processes: crossing over and independent assortment of chromosomes. These processes generate new combinations of genes and diverse sets of maternal and paternal chromosomes in the resulting haploid cells. In contrast, mitosis creates genetically identical daughter cells with minor variation due to mutations. Therefore, meiosis is responsible for significant genetic variation, while mitosis is not.

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Most popular questions from this chapter

If one follows 50 primary oocytes in an animal through their various stages of oogenesis, how many secondary oocytes would be formed? How many first polar bodies would be formed? How many ootids would be formed? If one follows 50 primary spermatocytes in an animal through their various stages of spermatogenesis, how many secondary spermatocytes would be formed? How many spermatids would be formed?

In this chapter, we focused on how chromosomes are distributed during cell division, both in dividing somatic cells (mitosis) and in gamete- and spore- forming cells (meiosis). We found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, answer the following questions. (a) How do we know that chromosomes exist in homologous pairs? (b) How do we know that DNA replication occurs during interphase, not early in mitosis? (c) How do we know that mitotic chromosomes are derived from chromatin?

What is the probability that, in an organism with a haploid number of \(10,\) a sperm will be formed that contains all 10 chromosomes whose centromeres were derived from maternal homologs?

Contrast spermatogenesis and oogenesis. What is the significance of the formation of polar bodies?

Describe the role of meiosis in the life cycle of a vascular plant.
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