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Meiosis

1. Explain, in words and not diagrams, the outcome of meiosis I. Do the same for meiosis II. Do not describe the details of each stage of meiosis I nor meiosis II.

2. Explain how a trisomy can occur. Why is trisomy 21 the most common autosomal trisomy in live-born infants?

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Bunny Greenfelder
Bunny GreenfelderLv2
28 Sep 2019

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Related questions

Nondisjuction is a cell division error in which either homologous chromosomes or sister chromatids fail to separate and thus do not migrate to opposite poles. It is responsible for conditions such as monosomy (one member of a chromosome pair is missing) and trisomy (three copies of a chromosome is present rather than two).

Nondisjunction can occur during the first or second meiotic division.

Part A- Jill is heterozygous for gene A and is going to have a child with Jack, who is homozygous recessive for gene A.

Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an egg that had undergone nondisjunction in meiosis I?
Check all that apply.

1)AAa

2)Aaa

3)aaa

4)Aa

5)aa

6)a

I put AAa, Aaa, Aa, but it was not correct

Part B-

Which of the following offspring genotypes could result from fertilization of a normal haploid sperm with an oocyte that had undergone nondisjunction in meiosis II?

Check all that apply.

1)AAa

2)Aaa

3)aaa

4)Aa

5)aa

6)a

Part E-

If Jack and Jill have a child with an aaa genotype, during which meiotic division, and in which parent, could nondisjunction have occurred?

Check all that apply.

1) Meiosis I in the mother

2 Meiosis II in the mother

3) Meiosis I in the father

4) Meiosis II in the father

The answer is not Meisis I in the mother

While working in a pathology lab, you are presented with an ovine blood sample (2n=54) that is suspected to have a genetic abnormality. You decide to karyotype the sample and diagnose trisomy 24.

1. Assume two hypothetical genes A and B are located on chromosomes 24 and 25 respectively. How many alleles for each gene will be present in the Primary oocyte, secondary oocyte and ovum that produced the animal with the abnormal karyotype indicated above – Provide answers for all possible scenarios.

2. Describe the number of autosomal chromosomes and chromatids in the Primary oocyte, Secondary oocyte and ovum that produced the animal with the abnormal karyotype indicated above – Provide answers for all possible scenarios

3. Another two hypothetical genes P and Q are located on chromosome 1; with the dominant alleles (P and Q) in coupling phase, and recessive alleles (p and q) in coupling phase on homologous chromosomes. Suppose a single crossing over occurs between the two genes during meiosis. What is the probability that the ovum that gave rise to karyotypically abnormal animal contains a chromatid with dominant alleles P and Q in coupling phase?

4. Suppose the animal had an XXY karyotype instead of trisomy 24. Did non-disjunction occur in the male or female parent (or both) and at which division(s), meiosis I or meiosis II?

Dude, a chromosomally normal male, is married to Dudette, who is also chromosomally normal. Their son, Dudester, has Klinefelter syndrome.

Please indicate whether each of the following events could have produced the Dudester.

In each case, assume that ALL other phases of cell division occur normally. For example, if the non-disjunction occurs in meiosis I in Dude, this implies that meiosis II in Dude is normal, and so is meiosis I and II in Dudette.

a. Non-disjunction in meiosis I in Dudette

b. Non-disjunction in meiosis II in Dudette

c. Non-disjunction in meiosis I in Dude

d. Non-disjunction in meiosis II in Dude

I've heard that its b and c, just c, or just a so im a little confused. Please explain why or why not.

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