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Answer:
Sometimes during anaphase, chromosomes will fail to separate properly. This is called nondisjunction. Nondisjunction results in cells with abnormal numbers of chromosomes. Instead, one pair of sister chromatids failed to split, resulting in one cell with 5 chromosomes and one cell with 3 chromosomes.
Explanation:
To get ready for mitosis, a cell must first undergo DNA replication during interphase. This process duplicates every strand of DNA so that there are two copies of every chromosome. The two copies are called sister chromatids and are attached at the centromere.
Once DNA replication is complete, nuclear division proceeds in four stages:
Prophase: chromosomes become visible, nuclear envelope disappears, kinetochores and spindle fibers form.
Metaphase: chromosomes align in the center of the cell at the metaphase plate.
Anaphase: chromosomes move outwards, towards opposite poles of the cell.
Telophase: reverse of prophase.
Each sister chromatid of a chromosome has spindle fibers attached to it. These spindle fibers begin to shorten and pull the sister chromatids apart at the centromere. This process of is called disjunction. Now each chromatid is called a daughter chromosome or just a chromosome.
The spindle fibers continue to shorten and move towards opposite ends or poles of the cell. There are also two distinct sets of chromosomes now, and each daughter cell will get one set.
Sometimes during anaphase, chromosomes will fail to separate properly. This is called nondisjunction. Nondisjunction results in cells with abnormal numbers of chromosomes. Instead, one pair of sister chromatids failed to split, resulting in one cell with 5 chromosomes and one cell with 3 chromosomes.
If the sister chromatids did not split equally during the anaphase of mitosis, nondisjunction may be caused.
What do you mean by Sister chromatids?
Sisters chromatids may be referred to as identical copies of chromosomes that are formed during the process of DNA replication.
If this situation happens it will result in one daughter cell having more chromosomes than normal, while the other daughter cell has fewer chromosomes than normal. This leads to the cause of various disorders like Turner syndrome, Down syndrome, Klinefelter syndrome, etc.
Therefore, if the sister chromatids did not split equally during the anaphase of mitosis, nondisjunction may be caused.
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