5. he importance of Morgan\'s fly experiments was that he discovered A, what a B
ID: 271150 • Letter: 5
Question
5. he importance of Morgan's fly experiments was that he discovered A, what a Barr bodv was. B. the basis of sex determination C. that some genes are sex linked D. what the cause of Klinefelter's syndrome is E. the phenomenon of non-disjunction 6.Cri du chat results from A. trisomy 13 B. trisomy 21 C. a deletion in chromosome 5 D. a translocation 7. Both males and females have Barr bodies in their mitochondria. (T/F) 8. Most cases of Down syndrome are due to nondisjunction in meiosis I.(T/F) 9. Nondisjunction can occur during A. meiosis I E meiosis II C. both A and B D. mitosis only 10. The probability of crossing over between two linked genes is greatest when the genes are A located on separate chromosomes B. close together on the same chromosome C, further apart on the same chromosome D. dominant
Explanation / Answer
5. B. The basis of sex determination.
Chromosomal theory of sex determination is based on the Morgan’s experiments with flies.the long X chromosome is responsible for femaleness and short Y chromosome is responsible for maleness.
6. C. Deletion in chromosome 5.
Deletion in p arm of chromosome number 5 result in cry-do-chat. It is also called as 5p syndrome or 5p deletion syndrome. Infant with 5p deletion has cat like high pitched cry.
7. false.
Barr body is a heterochromatic inactive X chromosome. Hence one Barr body is present in normal female (XX) because one X chromosome is inactivated. No Barr body is present in normal male (XY).
8. true.
Non disjunction in meiosis I is commonly observed in most cases of down syndrome.
9. C. Both A and B
Nondisjunction can occur during meiosisI or meiosis II. In any case it leads to ploidy.
10. A. Located on the separate chromosome.
Frequency of recombination is greatest in case of linked gene when the genes are on separate chromosome.
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