This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Chromosomal Theory of Inheritance”.
1. The chromosomal theory of inheritance was proposed by ____________
a) Mendel
b) Watson and Crick
c) Darwin
d) Sutton and Boveri
View Answer
Explanation: The chromosomal theory of inheritance was unknown in Mendel’s and Darwin’s time. It was proposed by Sutton and Boveri while Watson and Crick gave the structure of the DNA.
2. Which of the following doesn’t agree with the chromosomal theory of inheritance?
a) The genes are located on the chromosome
b) The genes on the same chromosome are always passed together
c) The genes are located linearly on the chromosomes
d) The distance between two genes can be mapped
View Answer
Explanation: Genes from the same chromosome can show independent assortment as well by recombination. However, very close gene tend to be linked and are passed on together.
3. If you cross a white eyed female drosophila with a red eyed male drosophila, what will be the colour of eyes for their male and female offspring?
a) Both red eyed
b) Both white eyed
c) Red eyed daughter and white eyed son
d) Red eyed son and white eyed daughter
View Answer
Explanation: The eye colour of Drosophila is an X linked gene. So as the female is homozygous recessive white and the male has on red allele and one Y chromosome, sons will only get Y chromosomes from father. Sons will thus be white eyed while daughters will be red eyed.
4. If there is a non-disjunction in the X chromosome, the progeny being XXY, what will be the constitution of the chromosome(s) in the gamete?
a) X and Y
b) X and XY
c) XX and Y
d) XXY with no separation
View Answer
Explanation: The non-disjunction results in the production of XXY. Then these alleles separate as X and XY respectively. The male progeny in this case will be XYY and the females XXY but the XXX dies due to no gene compensation.
5. The chromosomal theory of inheritance violates which of the following laws?
a) Law of dominance
b) Law of segregation
c) Law of independent assortment
d) None
View Answer
Explanation: The chromosomal theory of inheritance violated none of Mendel’s laws as the only difference was the genes being present in the chromosome, other than that the laws are as they were.
6. You observe a genetic trait which is a common occurrence in the male of a particular pedigree, this is possibly a ______________
a) X linked
b) Y linked
c) X linked recessive
d) Y linked dominant
View Answer
Explanation: If the gene has a sex bias it is certainly sex linked. In this case, it is a common occurance in the males only in a pedigree so it must be Y linked gene. There is no dominant recessive as Y is always hemizygous.
7. If you cross a red eyed pure breeding female Drosophila with a white eyed male, then the F1 males so produces were crossed with white eyed male, what will be the eye colour of their daughters and sons in F2?
a) Both daughters and sons red eyed
b) Daughters with both eye colour while sons with white eye
c) Both daughters and sons with both eye colours
d) Daughters with red eye and sons with white eyes
View Answer
Explanation: Eye colour is a sex linked trait. In this following case, the F1 male progeny was red eyed, as the father only gave the Y chromosome and not X which determines eye colour. Then similarly the F2 sons would be white eyed by allele from their mother, female will be red eyed as they get both allels.
8. If the genes are located in a chromosome as A—B—C—D—E—O—-T. Which of the gene pairs will have least probability of being inherited together?
a) C and D
b) A and T
c) A and B
d) O and T
View Answer
Explanation: Longer is the distance, lesser will be the probability of the two genes being inherited together as then there will be a greater chance of recombination.
9. If a gamete has 16 chromosomes, what will be the number of chromatids before anaphase 1?
a) 8
b) 16
c) 32
d) 64
View Answer
Explanation: There are 32 chromosomes but they are in duplicate chromatids so 64 is the number of chromatids before anaphase 1.
10. Which of the following can result from non-disjunction?
a) XY and XO
b) YY and XY
c) X and Y
d) XY and XXY
View Answer
Explanation: Non-disjunction in the male will produce XY and XO respectively. The other options are not suitable results of non-disjunction. In this case some part having XY will develop a male character with the parts with XO will have female characters.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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