Which one of the following never occurs during mitotic cell division ?...
Mitotic cell division, also known as mitosis, is a process where a cell duplicates its genetic material and divides into two identical daughter cells. During mitosis, the chromosomes condense, the nuclear envelope breaks down, and the spindle apparatus forms to segregate the chromosomes.
However, the pairing of homologous chromosomes occurs during a different type of cell division called meiosis, which is responsible for the production of gametes (sex cells). In meiosis, homologous chromosomes pair up during prophase I and undergo genetic recombination. This process increases genetic diversity and results in the formation of haploid cells. In mitosis, there is no pairing of homologous chromosomes; instead, each chromosome replicates and forms sister chromatids that separate during anaphase.
Which one of the following never occurs during mitotic cell division ?...
Explanation:
Mitotic cell division is a process by which a single cell divides into two identical daughter cells. It is an essential process for growth, development, and tissue repair in multicellular organisms. During mitosis, several events occur, such as movement of centrioles towards opposite poles, coiling and condensation of chromatids, and attachment of spindle fibers to kinetochores of chromosomes. However, pairing of homologous chromosomes does not occur during mitotic cell division. Here is a detailed explanation of each of these events:
Movement of centrioles towards opposite poles:
- Centrioles are small cylindrical structures found near the nucleus of animal cells.
- They play a crucial role in organizing the spindle fibers that are responsible for separating the duplicated chromosomes during cell division.
- During mitosis, the centrioles duplicate, and the pairs of centrioles move towards opposite poles of the cell.
- This movement is facilitated by microtubules and motor proteins.
Pairing of homologous chromosomes:
- Pairing of homologous chromosomes occurs during meiosis, not mitosis.
- Meiosis is a specialized form of cell division that occurs in reproductive cells to produce gametes (sperm and egg cells).
- In meiosis, homologous chromosomes, which contain similar genes but may have different versions of those genes, pair up and undergo crossing over, leading to genetic recombination.
- In mitosis, however, homologous chromosomes do not pair up. Instead, the duplicated chromosomes align at the equatorial plane of the cell before being separated into two daughter cells.
Coiling and condensation of chromatids:
- Prior to cell division, DNA replicates to form two identical copies called chromatids.
- These chromatids are held together at a region called the centromere.
- As mitosis progresses, the chromatids coil and condense, becoming more tightly packed.
- This coiling and condensation allow the chromosomes to be easily separated during cell division.
Spindle fibers attach to kinetochores of chromosomes:
- Spindle fibers are long protein structures that help in the movement of chromosomes during cell division.
- They attach to specific regions on chromosomes called kinetochores.
- Kinetochores are protein complexes located at the centromere of each chromatid.
- The attachment of spindle fibers to kinetochores allows for the proper alignment and separation of chromosomes during mitosis.
In conclusion, pairing of homologous chromosomes does not occur during mitotic cell division. This event is specific to meiosis, where homologous chromosomes pair up and undergo genetic recombination.
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