Genetics: In a large metropolitan hospital, cells from newborn babies are collec

Question

Genetics:

In a large metropolitan hospital, cells from newborn babies are collected and examined microscopically over a 5-year period. Among approximately 7500 newborn males, six have one Barr body in the nuclei of their somatic cells. All other newborn males have no Barr bodies. Among 7500 female infants, four have two Barr bodies in each nucleus, two have no Barr bodies, and the rest have one.

What is the cause of the unusual number of Barr bodies in a small number of male and female infants?

Select the six correct statements.

1. The unusual females with two Barr bodies result from a normal egg fusing with a sperm containing an X and a Y chromosome (nondisjunction during meiosis II in the father).
2. The unusual females with no Barr bodies result from fusion of a normal sperm containing an X chromosome with an egg that has no sex chromosomes (nondisjunction during meiosis I or II in the mother).
3. The unusual males with two X chromosomes result from an egg that has no sex chromosomes (nondisjunction during meiosis I or II in the mother) fusing with a sperm containing two X chromosomes (nondisjunction during meiosis I in the father).
4. The unusual females with no Barr bodies result from a normal egg fusing with a sperm containing no sex chromosomes (nondisjunction during meiosis I or II in the father).
5. The unusual females with two Barr bodies result from a normal egg fusing with a sperm containing two X chromosomes (nondisjunction during meiosis II in the father).
6. The unusual females with two Barr bodies result from fusion of a normal sperm containing an X chromosome with an egg containing two X chromosomes (nondisjunction during meiosis I or II in the mother).
7. The unusual males with two X chromosomes result from fusion of a normal sperm containing a Y chromosome with an egg containing two X chromosomes (nondisjunction during meiosis I or II in the mother).
8. The unusual males with two X chromosomes result from a normal egg fusing with a sperm containing an X and a Y chromosome (nondisjunction during meiosis I in the father).

Explanation / Answer

The correct statements are 2,4,5,6,7,8.

2. The unusual females with no Barr bodies result from fusion of a normal sperm containing an X chromosome with an egg that has no sex chromosomes (nondisjunction during meiosis I or II in the mother).

4. The unusual females with no Barr bodies result from a normal egg fusing with a sperm containing no sex chromosomes (nondisjunction during meiosis I or II in the father).
5. The unusual females with two Barr bodies result from a normal egg fusing with a sperm containing two X chromosomes (nondisjunction during meiosis II in the father).
6. The unusual females with two Barr bodies result from fusion of a normal sperm containing an X chromosome with an egg containing two X chromosomes (nondisjunction during meiosis I or II in the mother).
7. The unusual males with two X chromosomes result from fusion of a normal sperm containing a Y chromosome with an egg containing two X chromosomes (nondisjunction during meiosis I or II in the mother).
8. The unusual males with two X chromosomes result from a normal egg fusing with a sperm containing an X and a Y chromosome (nondisjunction during meiosis I in the father).

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