Question

question 21 nondisjunction or failure of chromosomes to separate can occur. a during mitosis of sex cells. b during meiosis i or ii of sperm or egg cells. c during meiosis i only of sperm or egg cells. d during meiosis ii of sperm or egg cells. e during meiosis i or ii in egg cells only. question 22 1 point which of the following human chromosomes usually does not exchange dna during meiosis? a x chromosome b y chromosome c chromosome 1 d chromosome 12 e chromosome 17

Explanation:

• Question 21: Nondisjunction occurs during meiosis (not mitosis) of sperm or egg cells. It can happen in meiosis I (homologous chromosomes fail to separate) or meiosis II (sister chromatids fail to separate).
• Question 22: The Y chromosome has a very small region of homology with the X chromosome, and most of its DNA does not participate in crossing - over (DNA exchange) during meiosis compared to autosomes (chromosome 1, 12, 17) and the X chromosome which has more regions for potential genetic exchange.

Answer:

• Question 21: B. during meiosis I or II of sperm or egg cells.
• Question 22: B. Y chromosome.