Cytogenetics Questions and Answers – Sex Determination in Mammals

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This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Sex Determination in Mammals”.

1. Mammals have _______________ type of sex determination.
a) XX/ XY
b) XX/ XO
c) ZZ/ ZY
d) Genic
View Answer

Answer: a
Explanation: Like Drosophila mammals also have XX/ XY mode of sex determination. However, the mechanism of sex determination in this case is much different.
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2. In Drosophila an organism with the genetic composition AA+XXY will be a normal female. What will be the case for mammal?
a) Normal female
b) Normal male
c) Klinefelter
d) Turner
View Answer

Answer: c
Explanation: IN mammals unlike drosophila the presence of Y chromosome determines maleness, thus XXY will have male characters. Again the presence of additional X chromosome will give rise to some female characters resulting in klinefelter.

3. In mammals which of the following will be a Turner?
a) AA + XXY
b) AA+ XYY
c) AA + XO/ XY
d) AA+ XO
View Answer

Answer: d
Explanation: AA+ XO will be a turner. This condition the female characters are underdeveloped due to the absence of one X chromosome. AA+ XO/XY on the other hand is intersex.
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4. Human being with genetic combination AA+ XXX will be non-viable like Drosophila with the same combination.
a) True
b) False
View Answer

Answer: b
Explanation: In human beings unlike drosophila there is dosage compensation for the extra X chromosome. Due to this reason this person will be a viable female.

5. The gene for sex determination in mammals is _________ and it is located in ___________
a) MAT, Y
b) SRY, Y
c) MAT, X
d) SRY, X
View Answer

Answer: b
Explanation: SRY is the gene in Y chromosome that is necessary for the development of male characters. It is located in the Y chromosome. The MAT is sex determining factor for yeast.
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6. In an experiment, you add the short arm of Y chromosome to a cell line with composition AA+ XX. What will you see?
a) The cell rejects the Y chromosome
b) The cell develop female character
c) The cell develop male character
d) The cell develop neuter gender character
View Answer

Answer: c
Explanation: The short arm of the Y chromosome is carrying the SRY gene which determines the sex of the organism. Thus introduction of Y chromosome will promote the development of male characters.

7. Which of the following is wrong for sex chromosome?
a) X chromosome is larger than Y
b) Female human are homozygous
c) Y chromosome carries TDF
d) All genes present on Y chromosome are unique to it
View Answer

Answer: d
Explanation: There is a homologous region between the X and Y chromosome, and genes in Y chromosome in that area is not unique to it. TDF is another name used for SRC gene that is also located on Y chromosome.
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8. Klinefelter syndrome results due to ____________
a) Non-disjunction in the male gamete
b) Non-disjunction in the female gamete
c) Gradual loss of chromosome
d) Non-disjunction in any of the gametes
View Answer

Answer: d
Explanation: Klinefelter syndrome results from a genetic combination AA+ XXY; this can result from non-disjunction in either male or female gamete.

9. A person with a genetic composition AA+XYY composition. The non-disjunction is in the __________ parent and in _____________ meiotic division.
a) Male, 1st
b) Male, 2nd
c) Female, 1st
d) Female, 2nd
View Answer

Answer: b
Explanation: A female can never have Y chromosome to start with so the non-disjunction is in a male. If the non-disjunction was in 1st division improper segregation of X and Y will produce XY gamete. Here there is an improper 2nd division where 2Y generated in meiosis 2 moves to same pole giving YY gamete.
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10. A female with AA+ XXX can only result from female parental non-disjunction.
a) True
b) False
View Answer

Answer: b
Explanation: Both 1st and 2nd meiotic non-disjunction in female can give AA+ XXX combination. Also 2nd meiotic non-disjunction in male gamete where two X chromosome moves to same pole can also give this result.

11. The intersex is produced by ________________
a) Fusion of a male and female zygote
b) Loss of X chromosome from some cells
c) Loss of Y chromosomes from some cells
d) Gain of X or Y chromosome due to non-disjunction
View Answer

Answer: c
Explanation: Intersex has the combination AA+ XO/XY. Presence of Y chromosomes develops male character so AA+XY cells are male. Absence of Y gives female characters so AA+XO gives female, this is due to loss of Y chromosome from these cells. Overall it results in intersex.

Sanfoundry Global Education & Learning Series – Cytogenetics.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter