This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Dynamic Mutation and Anticipation”.
1. Dynamic mutation is _________________
Explanation: Dynamic mutation is an unstable genetic phenomenon which can be passed to the next generation, so it is heritable.
2. Dynamic mutation depends on which of the following?
a) Presence of a gene
b) The number of repeats
c) The location of the gene
d) The methylation state of the gene
Explanation: Dynamic mutation is the function of the number of copies of a particular gene present in an individual. The replication product of a dynamic mutation will usually have a different likelihood of mutation than its predecessor.
3. Dynamic mutation is mainly due to _____________ nucleotide repeats.
Explanation: The tri-nucleotide repeat sequences determine the dynamic mutation. This is due to the slippage of the replication machinery during replication.
4. Anticipation is not seen in which of the following?
a) Fragile X chromosome
b) Duchenne muscular dystrophy
c) Myotonic dystrophy
d) Huntingtons’s disease
Explanation: In case of Duchenne muscular dystrophy the disease is dependent of age of onset but not due to anticipation. The other 3 options are due to the number of tri-nucleotide repeats.
5. Fragile X chromosome is due to the ____________ repeats?
Explanation: The number of CGG repeats in an individual determines the fragile X chromosome disease severity. This is due to anticipation.
6. Which of the following individuals will have fragile X chromosome?
a) 6 repeats of CGG
b) 50 repeats of CGG
c) 150 repeats of CGG
d) 700 repeats of CGG
Explanation: The normal number of CGG repeats in an individual is about 6-50. If a daughter has 50-200 repeats then the next generation is likely to have 200-1300 repeats leading to the disease. However, the daughter doesn’t show the defect.
7. Foe fragile X chromosome which of the following is wrong?
a) The father having 50 nt repeats or above leads to disease in daughter
b) Daughter has 50-200 repeats
c) The grandson has 200-1300 repeats
d) The grandson shows the disease phenotype
Explanation: The father having a repeat beyond a particular threshold say 50 will pass the gene to daughter. In the daughter due to anticipation the gene could be 50-200 times repeated. Only in the next generation number of repeat will be 200-1300 and they will show the phenotype.
8. Which of the following can explain anticipation?
a) Due to slippage of the trinucleotide repeats we will see gradually all the repeat number increases as does the defective phenotype
b) The child always expresses the phenotype more severely than unaffected parent
c) The number of repeat beyond a particular threshold leads to improper replication
d) It is inherited like linkage
Explanation: In case of anticipation there is a normal range of number of repeats which can be faithfully replicated. If the number of repeats is beyond a threshold then the faithful replication is lost and massive increase in number is seen in the next generation and yet more in the next.
9. Fragile X chromosome affects the __________ gene.
Explanation: The FMR1 gene is affected by the fragile X chromosome; in this case the X chromosome inactivating RNA is malformed in the individual.
10. Only sons of the daughter whose father was NTM will be affected by the disease- fragile X chromosome.
Explanation: The NTM or non-transmitted males will pass the disease to the daughter who can pass it to both her sons and daughters. It is not like the X linked gene inheritance.
11. Huntington’s disease is due to the __________ trinucleotide repeats.
Explanation: CAG repeat numbers determine the Huntington’s disease in an individual. CGG repeats are determinant for the fragile X chromosome.
12. What is the threshold number of repeats in Huntington’s disease?
Explanation: If the number of CAG repeats in an individual is below 36 then the person will show normal phenotype. If larger than that then Huntington’s disease will result.
13. For very large number of repeats in Huntington’s disease, the phenotype can appear at 20 years of age.
Explanation: Huntigton’s is an X linked dominant disease that is expressed in an individual beyond 30 years of age if they have more than 36 CAG repeats. If the number of repeats of CAG is much more the gene can find its expression at 20 years of age as well.
14. Dysgenic effect of medicine is ______________
a) Disobeying Mendalian principle
b) Against Darwin’s theory
c) Leads to strengthening of the society
d) Diseases become scarce
Explanation: Modern medicine is dysgenic as it counters the effect of natural selection by Darwin. As a result, children who would ordinarily have died young now survive to have children of their own, which inevitably leads to genetic degradation of the entire society.
15. Phenyl ketone urea is expected to increase __________ by the next 30 years due to Dysgenic effect of medicine?
Explanation: PKU is a disease where the individual can have a normal life if they are on a special diet. Then the persons are able to live and reproduce and pass on the disease, who would otherwise have died. This could result in 300 % increase in the PKU in next 30 years.
Sanfoundry Global Education & Learning Series – Cytogenetics.
To practice all areas of Cytogenetics, here is complete set of 1000+ Multiple Choice Questions and Answers.