This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Chromosomal Abnormalities : Translocation – 2”.
1. ____________ is mandatory for autonomous transposition.
a) Internal gene
b) Transposase
c) 3’ concensus of region upstream to transposition
d) Branch point A
View Answer
Explanation: Recombinase such as transposase or integrase is mandatory for transposition as they help in recombination at terminal repeats. Branch poit A is needed in splicing and internal gene is not mandatory.
2. What percentage of the human genome is transposition related?
a) 2%
b) 10%
c) 50%
d) 80%
View Answer
Explanation: 50% of the human and maize genetic elements in involved in transposition. This is a huge amount and shows the evolutionary importance of transposition.
3. Non-autonomous transposons can’t transpose. State whether the statement is true or false.
a) True
b) False
View Answer
Explanation: Non-autonomous transposons lack the recombinase that aids in transposition. However, they can transpose with the help of the recombinase from another trasposon.
4. Transposition doesn’t require much sequence homology between two genetic molecules, based on this hey can help in _____________
a) Homologous DSB repair
b) Non-homologous end joining
c) Site-specific recombination
d) Homologous recombination
View Answer
Explanation: In case of site specific recombination there would be very little or no homology between the donor and recipient site, this can be imposed by translocation. Translocation doesn’t play a part in homologous repair or NHEJ.
5. Choose the wrong one out for insertion sequence.
a) Insertion sequences are transposons
b) Insertion sequences range from 5kb to 30kb
c) Insertion sequences only carry genes for their transposition
d) Insertion sequences have terminal IR
View Answer
Explanation: Insertion sequences are very short transposons which range from 768 bp to 5 kb, they indeed have genes only needed for transposition and there is an inverted repeat at two terminals.
6. In an experiment you develop immune response in mice against salmonella flagellar antigen. However, you observe the infection still persisted. Which if a likely possibility if immune system is functioning properly?
a) Salmonella shed its flagella
b) The antigen lost its specificity gradually
c) The flagella antigen changed
d) Infection was not due to salmonella
View Answer
Explanation: In salmonella, the flagellar antigen is target for immune response. His antigen’s phase can vary with presence of insertion sequence within the gene. In this case change of antigen could lead to a loss of specificity by the immune system.
7. Choose the wrong option.
a) Transposons have trasposase along with other genes
b) Transposons lack inverted terminal repeats
c) Transposons have insertion sequences within it
d) Class III transposons are called MITES
View Answer
Explanation: Transposons have Inverted Terminal Repeats, further they may have two insertion sequences at two ends. They have many genes which often include antibiotic resistance gene.
8. Which of the following transpose using RNA intermediate?
a) Class I transposon
b) Class II transposon
c) Class III transposon
d) Class IV transposon
View Answer
Explanation: Class I transpose or retro transposons are those that 1st transcribe the transposon DNA to RNA, then using reverse transcriptase enzyme they insert the sequence within the recipient DNA.
9. Which of the following is not true about conservative transposition?
a) It creates direct repeat sequences on either side
b) It is Copy-Paste mechanism
c) Transesterification reaction takes place
d) Class II transposons have this mechanism
View Answer
Explanation: Conservative or non-replicative transposition acts through cut and paste mechanism. The donor site loses the transposon which is inserted in the recipient generating direct repeats. It is seen in class II transposons.
10. Which of the following is not seen in cut-paste transposition, but seen in copy-paste method?
a) Synaptic complex
b) Strand transfer
c) Transposase
d) Resolvase
View Answer
Explanation: In addition to what is required in cut-paste mechanism, replicative transposition also requires enzyme resolvase to resolve the structure formed after strand transfer reaction.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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