Question

Homologous chromosomes gets separate during (a) Metaphase-I (b) Anaphase-I (c) Anaphase-II (d) Telophase-I

Short answer

The homologous chromosomes separate during Anaphase-I, so the correct answer is (b) Anaphase-I.

Step-by-step solution

Understanding stages of Meiosis

Meiosis has two division stages: Meiosis I and Meiosis II. Each stage has four phases, namely Prophase, Metaphase, Anaphase and Telophase. During Meiosis I, homologous chromosomes pair up and exchange genetic material (in Prophase I), line up at the equatorial plane (in Metaphase I), and separate (in Anaphase I). During Meiosis II, sister chromatids separate.

Delay in Chromosomes Separation

In the Anaphase-I of Meiosis-I, the homologous chromosomes separate and move to opposite poles. Therefore, Anaphase-I is the phase of meiosis in which homologous chromosomes are separated.

Identifying the correct option

Looking at the options provided, option (b) Anaphase-I is where the homologous chromosomes are separated.

Key concepts

Homologous Chromosomes

Identifying homologous chromosomes is crucial in understanding the intricacies of meiosis. In diploid organisms, each cell contains pairs of chromosomes, one from the mother and one from the father. These pairs are called homologous chromosomes because they are similar in size, shape, and genetic content. However, they are not identical as they carry different versions of the same genes, known as alleles.

During meiosis, specifically in the Prophase I stage, these homologous chromosomes undergo a process called synapsis, where they pair up tightly. This allows for crossing over, where segments of DNA are exchanged between them, resulting in genetic variation. Understanding the role of homologous chromosomes is fundamental because their separation and subsequent distribution into gametes - sperm or eggs, depending on the sex of the organism - helps ensure genetic diversity within a species.

Anaphase-I

The precise timing of chromosome separation is integral to successful cell division. Anaphase-I marks a pivotal moment in meiosis I, the first division in the meiotic process. During this phase, each pair of homologous chromosomes, which were previously aligned along the metaphase plate, is pulled apart by spindle fibers. The key feature of Anaphase-I is that, unlike mitosis where sister chromatids separate, it is the homologous chromosomes themselves that are segregated to opposite poles of the cell.

To visualize this: imagine each chromosome being gently tugged away by these spindle fibers, moving like dancers to opposite sides of the cellular 'ballroom', ensuring that each resulting daughter cell receives just one chromosome from each original homologous pair. This stage is essential for genetic diversity as it ensures recombination has occurred and the resultant cells each have unique genetic combinations.

Chromosomes Separation

The separation of chromosomes is a central event in both forms of cell division: mitosis and meiosis. In the context of meiosis, chromosomes separation occurs during two distinct phases: Anaphase-I and Anaphase-II. As highlighted previously, Anaphase-I is characterized by the separation of homologous chromosomes. Each homologous pair is split up, with one chromosome migrating to one pole of the cell and its partner moving to the opposite pole. This process is facilitated by the shortening of spindle fibers which attach to a specific area, known as the centromere, on each chromosome.

During Anaphase-II, which is more akin to what happens during mitosis, the sister chromatids that made up each individual chromosome are pulled apart. This separation is vital for the formation of haploid cells, which contain only one set of chromosomes, ensuring proper distribution of genetic material in gametes. Any errors in this process can lead to gametes with an incorrect number of chromosomes, leading to disorders such as Down syndrome or infertility.

Stages of Meiosis

Meiosis can be seen as a choreographed spectacle that unfolds in several steps, making it important to understand each stage thoroughly. It occurs in two overarching rounds of division: Meiosis I and Meiosis II. Each round includes four stages: Prophase, Metaphase, Anaphase, and Telophase, and are succeeded by cytokinesis which divides the cell's cytoplasm.

In Meiosis I, homologous chromosomes separate - this is known as reductional division, as the cell is reduced from diploid to haploid in terms of chromosome number. Meiosis II resembles standard mitosis, with the separation of sister chromatids - termed equational division, as it maintains the haploid state. The division stages of meiosis are critical for sexual reproduction and genetic diversity, as they shuffle and halve the genetic material to be passed on, facilitating evolution and adaptation in life on Earth.