Question

Meiosis is a necessary part of sexual reproduction because it a. divides two nuclei into four new nuclei b. reduces the chromosome number for gametes c. produces clones that can cross over

Short answer

The correct answer is b. Meiosis reduces the chromosome number for gametes.

Step-by-step solution

Understanding Meiosis

Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. This process is crucial for sexual reproduction because it ensures genetic diversity and maintains a consistent chromosome number across generations.

Analyzing Option A

Option A states that meiosis divides two nuclei into four new nuclei. While meiosis does result in four cells, the key function of meiosis is not the mere division of nuclei but rather the reduction of chromosome number.

Examining Option B

Option B suggests meiosis reduces the chromosome number for gametes. This is correct because meiosis transforms a diploid cell (with two sets of chromosomes) into haploid gametes (with one set of chromosomes). This reduction is essential for generating eggs and sperm that, upon fertilization, restore the diploid chromosome number.

Evaluating Option C

Option C states that meiosis produces clones that can cross over. Meiosis does involve crossing over during Prophase I, which introduces genetic variation. However, the term 'clones' is misleading, as clones imply identical genetic material, whereas meiosis provides genetic variation rather than clones.

Choosing the Correct Answer

After reviewing the options, the correct answer is Option B: Meiosis reduces the chromosome number for gametes. This is the fundamental purpose of meiosis, aligning with the requirements of sexual reproduction for maintaining genetic consistency yet allowing variability.

Key concepts

Chromosome reduction

During meiosis, one of the main objectives is the reduction of chromosomes. Imagine our body cells; they typically contain two sets of chromosomes, which we call diploid. However, for sexual reproduction, a different approach is needed. Here's where meiosis plays its part.

• Diploid to Haploid: The cell begins as a diploid, meaning it has two sets of chromosomes, one from each parent.
• Reduction Division: Meiosis includes two division phases. The first phase reduces the chromosome number by half, resulting in cells with only one set of chromosomes, known as haploid.

This chromosome reduction is vital because it ensures that when an egg and sperm unite during fertilization, the resulting offspring have the correct number of chromosomes, thus maintaining genetic stability.

Gametes

Gametes are the specialized cells responsible for sexual reproduction. They come in two types: sperm and eggs. Generally, gametes are the result of meiosis, where their primary role is to carry genetic information to the next generation.

• Formation: As a product of meiosis, gametes arise with half the chromosome number of typical body cells.
• Function: These haploid cells play a crucial role in ensuring genetic continuity and variety. When gametes fuse during fertilization, they restore the diploid state of the new organism.

This entire process through gametes allows for the mixing of genetic material from two parents, which is essential for both creating offspring and allowing evolutionary processes.

Genetic diversity

Genetic diversity is the variation in genetic material present in a population that ensures adaptability and evolution. Meiosis plays a crucial role here by introducing variation through two key mechanisms.

• Crossing Over: During Prophase I of meiosis, homologous chromosomes exchange segments. This mixing of genes between chromosomes results in new genetic combinations.
• Independent Assortment: Chromosomes are distributed randomly into gametes. Consequently, each gamete contains a different set of genes. This random assortment results in a varied gene pool.

These mechanisms work together to ensure that each generation is genetically unique. Such diversity is invaluable for survival, as it enhances a population's ability to adapt to new environments or survive challenges like diseases.