In cell division, why is meiosis often referred to as reduction division?

Introduction / Context:
Cells divide by two main processes: mitosis and meiosis. Mitosis produces genetically similar daughter cells with the same chromosome number as the parent, while meiosis produces cells with half the chromosome number. Meiosis is especially important in sexual reproduction because it forms gametes such as sperm and ova. For this reason, meiosis is often called reduction division. This question asks you to explain the basis for that term.

Given Data / Assumptions:

• The process under discussion is meiosis, not mitosis.
• We are asked why it is called reduction division.
• Options suggest different types of reductions (chromosome number, cell size, gene number, organelles, metabolic rate).
• We assume a diploid organism, where the parent cell has a full set of paired chromosomes.

Concept / Approach:
Meiosis consists of two successive divisions: meiosis I and meiosis II. In meiosis I, homologous chromosomes pair up and then separate, so that each daughter cell receives only one chromosome from each pair. This reduces the chromosome number from diploid (2n) to haploid (n). Meiosis II then separates sister chromatids, similar to mitosis, but the chromosome number remains haploid. As a result, meiosis produces gametes with half the chromosome number of the parent germ cell. When fertilisation occurs, two haploid gametes fuse to restore the diploid number. Thus, the key reduction is in chromosome number, not in cell size, organelles, or genes.

Step-by-Step Solution:
Step 1: Recall that the parent germ cell entering meiosis is usually diploid, having two sets of chromosomes (2n). Step 2: During meiosis I, homologous chromosomes pair, exchange segments (crossing over), and then separate into different cells. Step 3: After meiosis I, each daughter cell has only one member of each homologous pair, so the chromosome number becomes haploid (n). Step 4: Meiosis II separates sister chromatids but does not change the haploid number. Step 5: At the end of meiosis, four haploid cells are produced from one diploid parent cell. Step 6: This halving of chromosome number is the reason meiosis is called reduction division.

Verification / Alternative check:
Genetics and cell biology texts repeatedly define meiosis as a type of division that reduces the chromosome number to half in the resulting gametes. They explain that this reduction is essential so that when two gametes fuse during fertilisation, the offspring have the correct diploid number rather than double. No reputable source describes meiosis primarily in terms of reducing cell size or organelle count. This confirms that reduction refers to chromosome number.

Why Other Options Are Wrong:
Because it reduces the size of the cell to half of the original cell: Cell size can vary and is not the defining feature of meiosis. Because it reduces the number of genes present in the genome: The set of genes remains essentially the same; only the number of chromosome sets changes. Because it reduces the number of cell organelles to half in each division: Organelles may be distributed, but this is not the primary reason for the term reduction division. Because it reduces the rate of all metabolic reactions by half: Meiosis is not defined based on metabolic rate changes.

Common Pitfalls:
Students sometimes think reduction means shrinking of the cell or loss of genes, which is misleading. Another frequent confusion is between meiosis and mitosis, especially in terms of chromosome number changes. To avoid these errors, focus on the key genetic concept: meiosis reduces the chromosome number from diploid to haploid, ensuring genetic stability across generations.

Final Answer:
The correct answer is: Because it reduces the chromosome number in daughter cells to half of the parent cell.