Nondisjunction can result in __________.
the number of cells produced being more than four
cells in which crossing-over did not occur
mitosis occurring instead of meiosis
cells with abnormal numbers of chromosomes
answer is cells with abnormal numbers of chromosomes
Nondisjunction can result in cells with abnormal numbers of chromosomes.
To understand why nondisjunction can lead to abnormalities in chromosome numbers, let's explain the process of nondisjunction and its consequences.
Nondisjunction is an error that can occur during cell division, specifically during the separation of chromosomes. It happens when chromosomes fail to separate properly, either in meiosis (the process that produces sperm or eggs) or mitosis (the process that produces new cells for growth and repair).
During meiosis, pairs of chromosomes line up in the center of the cell and are supposed to separate evenly to produce haploid cells (cells with half the normal chromosome number). In mitosis, chromosomes line up and separate to produce two genetically identical diploid cells (cells with the normal chromosome number).
However, in the case of nondisjunction, the chromosomes may not separate correctly. This can result in several possible outcomes:
1. Cells with abnormal numbers of chromosomes: If nondisjunction occurs in meiosis, it can lead to gametes (sperm or eggs) with an incorrect number of chromosomes. For example, instead of producing four haploid cells (each with one copy of each chromosome), nondisjunction can result in gametes with an extra copy of a particular chromosome (trisomy) or a missing copy (monosomy). When these abnormal gametes are involved in fertilization, the resulting zygote will have an abnormal number of chromosomes, which can lead to genetic disorders like Down syndrome (trisomy 21) or Turner syndrome (monosomy X).
2. The number of cells produced being more than four: During meiosis, if nondisjunction occurs and one pair of chromosomes fails to separate, it can lead to an uneven distribution of chromosomes. As a result, one cell may receive an extra set of chromosomes while another cell receives fewer chromosomes. This can lead to the production of more than four cells with abnormal chromosome numbers.
3. Cells in which crossing-over did not occur: Crossing-over is the exchange of genetic material between homologous chromosomes during meiosis. It helps in increasing genetic diversity. However, if nondisjunction happens before or during crossing-over, it can result in cells that lack this genetic exchange process.
In summary, nondisjunction can result in cells with abnormal numbers of chromosomes, leading to genetic disorders. It can also lead to an uneven distribution of chromosomes or affect the occurrence of crossing-over during meiosis.