Problem 13 - Biology of Humans: Concepts, Applications, and Issues

Question

The stage of meiosis during which sister chromatids separate is _______________.

Step-by-Step Solution

Answer

Anaphase II

Step 1: Understand Meiosis Stages

Meiosis occurs in two main stages: Meiosis I and Meiosis II. Each of these stages involves several sub-stages: Prophase, Metaphase, Anaphase, and Telophase.

Step 2: Identify Key Events

In Anaphase I of Meiosis I, homologous chromosomes separate, not sister chromatids. In Anaphase II of Meiosis II, sister chromatids separate.

Step 3: Determine the Specific Stage

Since the question asks about the separation of sister chromatids, focus on Anaphase II of Meiosis II. This is where the sister chromatids are pulled to opposite poles of the cell.

Step 4: Conclusion

Based on the analysis, the stage of meiosis during which sister chromatids separate is Anaphase II.

Key Concepts

sister chromatids

Sister chromatids are essentially identical copies of a single chromosome. They are formed during DNA replication in the S phase of the cell cycle. Each chromosome duplicates to ensure that each new cell will get a full set of chromosomes after cell division.

To dive deeper, a chromosome before replication consists of a single DNA molecule. After replication, each chromosome consists of two sister chromatids, joined at a region called the centromere. These chromatids remain attached until they are separated during cell division.

The concept of sister chromatids is crucial in understanding how genetic information is accurately passed from one cell generation to the next. Without the process of forming and eventually separating sister chromatids, cells wouldn't be able to distribute genetic material correctly during division.

Anaphase II

Anaphase II is a critical phase within Meiosis II. During this stage, sister chromatids finally separate from each other and move toward opposite poles of the cell.

To visualize: Imagine two parallel lines representing sister chromatids aligned in the center of the cell. During Anaphase II, these lines split and move in opposite directions, ensuring each new cell will receive a copy of each chromatid.

This step is distinct from Anaphase I of Meiosis I, where it is homologous chromosomes—not sister chromatids—that separate. The separation that occurs during Anaphase II helps ensure genetic diversity, as each resulting cell contains a unique set of genes.

Meiosis II

Meiosis II follows Meiosis I and is somewhat similar to mitosis, but with half the number of chromosomes.

Key steps in Meiosis II include:

• Prophase II: Chromosomes condense, and the nuclear envelope breaks down. New spindle fibers form.
• Metaphase II: Chromosomes align at the cell's equator, or metaphase plate.
• Anaphase II: Sister chromatids separate and move towards opposite poles.
• Telophase II: Nuclear membranes reform around the chromatids now called chromosomes, and the cell divides.

It's important to note that Meiosis II results in four genetically distinct haploid cells from the original diploid cell. Each of these resultant cells contains half the chromosome number compared to the original, maintaining genetic diversity. This process is essential for sexual reproduction in eukaryotic organisms.