What is a nondisjunction?

Question

View Available Hint(s)for Part A

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell
An error in which a diploid cell or organism has an extra chromosome of one type, producing a chromosome number of 2n + 1
An error in which a diploid cell or organism lacks a chromosome of one type, producing a chromosome number of 2n - 1
None of the above
Part B
When can nondisjunction occur? Choose the best answer.
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In meiosis, when homologous chromosomes fail to separate
In meiosis, when sister chromatids fail to separate
In mitosis, when sister chromatids fail to separate
All three answers are correct.
Part C
Which syndrome is characterized by the XO chromosome abnormality?

Trisomy X
Klinefelter syndrome
Turner syndrome
Down syndrome
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Part D
What kind of cell results when a diploid and a haploid gamete fuse during fertilization?
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A triploid cell
A monosomic cell
A trisomic cell
A monoploid cell
Part E
Of the following chromosomal abnormalities, which type is most likely to be viable in humans?
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Monosomy
Triploidy
Trisomy
Haploidy
Part F
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?
View Available Hint(s)for Part F

No error occurred; these are normal gametes.
A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.
A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell.
A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.
Part G
If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred?
View Available Hint(s)for Part G

A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.
A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell.
No error occurred; these are normal gametes.
A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

Answer 1

Here are the answers for each part of your questions regarding nondisjunction and related concepts:

Part A: What is a nondisjunction?

• Answer: An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell.

Part B: When can nondisjunction occur? Choose the best answer.

• Answer: All three answers are correct.

Part C: Which syndrome is characterized by the XO chromosome abnormality?

• Answer: Turner syndrome

Part D: What kind of cell results when a diploid and a haploid gamete fuse during fertilization?

• Answer: A triploid cell

Part E: Of the following chromosomal abnormalities, which type is most likely to be viable in humans?

• Answer: Trisomy

Part F: If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?

• Answer: A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

Part G: If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred?

• Answer: A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

If you have further questions or need clarification on any of these topics, feel free to ask!