Question

Which of the following is one of the very important differences between mitosis and meiosis? a. Chromosomes align midway between spindle poles only in meiosis. b. Homologous chromosomes pair up only in meiosis. c. DNA is replicated only in mitosis. d. Sister chromatids separate only in meiosis. e. Interphase occurs only in mitosis.

Short answer

Option b: Homologous chromosomes pair up only in meiosis.

Step-by-step solution

Understanding Mitosis and Meiosis

Mitosis is a type of cell division that results in two genetically identical daughter cells, while meiosis leads to four genetically diverse daughter cells. One key feature of meiosis is the pairing of homologous chromosomes, which does not occur in mitosis.

Evaluate Each Option

Consider each option to see if it describes a unique feature of meiosis as compared to mitosis. - Option a: Chromosomes align midway in both mitosis and meiosis. - Option b: Homologous chromosomes pair only in meiosis. - Option c: DNA is replicated during interphase before both processes. - Option d: Sister chromatids separate in both processes. - Option e: Interphase precedes both mitotic and meiotic divisions.

Identifying the Most Correct Option

Based on the evaluation: - The pairing of homologous chromosomes is unique to meiosis and does not happen in mitosis. Thus, Option b is correct, because pairing up of homologous chromosomes is a key difference specific to meiosis.

Key concepts

Cell Division

Cell division is a fundamental process by which cells reproduce, enabling organisms to grow, develop, and repair tissues. There are two primary types of cell division: mitosis and meiosis.
Mitosis is used for growth and repair, producing two genetically identical daughter cells from one parent cell. Each daughter cell has the same number of chromosomes as the parent cell, ensuring continuity of genetic information.
Meiosis, however, is specialized for sexual reproduction. Unlike mitosis, it creates four daughter cells, each with half the number of chromosomes of the parent cell. This reduction is crucial, as it allows for the fusion of male and female gametes during fertilization, restoring the full chromosome count in the offspring.
Both processes start with the replication of DNA during interphase, but what follows distinguishes them significantly. Mitosis includes phases like prophase, metaphase, anaphase, and telophase, completed with cytokinesis. In contrast, meiosis consists of meiosis I and II, each encompassing similar phases but leading to genetic diversity through crossing over and independent assortment.

Homologous Chromosomes

Homologous chromosomes are pairs of chromosomes, one from each parent, that are similar in shape, size, and genetic content. They carry alleles for the same genes at corresponding locations, but the alleles may differ between homologs.
In mitosis, homologous chromosomes do not pair up. Instead, each chromosome duplicates and sister chromatids are separated to form two identical daughter cells.
In meiosis, however, homologous chromosomes undergo a crucial event known as synapsis during prophase I. This pairing allows for crossing over, where homologous chromosomes exchange segments of DNA. This recombination generates genetic variation among the resulting gametes, which is not possible in mitosis.
Understanding how homologous chromosomes function in meiosis, versus their role in mitosis, highlights the unique mechanisms that contribute to genetic diversity and the propagation of traits from one generation to the next.

Genetic Diversity

Genetic diversity refers to the variety of genes within a species. It is vital for populations to adapt to changing environments and resist diseases. Meiosis plays a critical role in enhancing genetic diversity through two main mechanisms.
First, during prophase I of meiosis, homologous chromosomes exchange genetic material through crossing over. This process shuffles genes and creates new combinations, ensuring that gametes have different genetic make-ups.
Second, meiosis includes a phenomenon called independent assortment. During metaphase I, homologous chromosome pairs align randomly along the cell equator. This random orientation determines which homologous chromosome ends up in each daughter cell, adding to the genetic variation among gametes.
These meiotic processes ensure that each sperm or egg cell is genetically unique, contributing to the genetic diversity observed in sexually reproducing populations. This diversity is essential for the survival and evolution of species as it enhances the chances for individuals to adapt over generations.