Gene Manipulation Multiple Choice Questions on “Manipulation of Large Genes”.
1. Which of the following can be used to clone very large fragments of DNA?
A. M13
B. Lambda phage
A. Agrobacterium
D. Yeast artificial chromosome
Answer: D
Clarification: Yeast artificial chromosomes can be used to clone very large fragments of DNA. Their segregative ability is determined by their size.
2. Less than what size of YAC is its centromere function impaired?
A. 2 kb
B. 10 kb
A. 20 kb
D. 5 kb
Answer: C
Clarification: If the size of the YAC is less than 20 kb then centromere function is impaired whereas much larger YACs segregated normally.
3. Average insert size can be increased of a YAC vector by which of the following techniques?
A. PFGE
B. CHEF
A. PCR
D. Electroporation
Answer: A
Clarification: By removing small DNA fragments by Pulsed-field gel electrophoresis (PFGE), the average insert size can be increased to 350 kb.
4. Polyamines prevent _____________
A. RNA degradation
B. DNA degradation
A. Hybridization
D. Protein degradation
Answer: B
Clarification: By including polyamines to prevent DNA degradation, Larin was able to construct YAC libraries from mouse and human DNA.
5. 10-60% of clones in existing YAC libraries represent _______________
A. Hybridization
B. Improper annealing
A. Chimeric sequences
D. Inactivated genes
Answer: C
Clarification: An operational problem with YAC vectors is that 10-60% of clones in existing libraries represent chimeric DNA sequences.
6. Chimeras in YAC libraries may arise due to _________
A. Increased temperature
B. Poor handling
A. Inactivated enzymes
D. Co-ligation
Answer: D
Clarification: Chimeras can arise by co-ligation of DNA inserts in vitro prior to yeast transformation, or by recombination between two DNA molecules.
7. Chimeras can possibly be detected by which technique?
A. Hybridization
B. Electroporation
A. UV radiation
D. Spectroscopy
Answer: A
Clarification: Chimeras can be detected by in situ hybridizations of the YAC to metaphase chromosomes: hybridization to two or more chromosomes or to geographically disparate regions of the same chromosome.
8. Many clones of the YACs are __________
A. Contaminated
B. Small
A. Unstable
D. Indistinguishable
Answer: C
Clarification: An operation problem with the Yeast Artificial Chromosomal vectors is that many clones are unstable and tend to delete internal regions from their inserts.
9. Deletions in the clones of YAC vectors can occur both during transformation process and _______________ of transformants.
A. Meiotic division
B. Mitotic growth
A. Ligation
D. Digestion
Answer: B
Clarification: Using a model system, Kouprina were able to show that the deletions can be generated during the transformation process and during mitotic growth of the transformants.
10. Rad52 mutation can reduce the frequency of _________ in YACs.
A. Temperature change
B. Deletions
A. Mutations
D. Hybridization
Answer: B
Clarification: Ling showed that the frequency of deletion formation could be reduced by use of a strain rendered deficient as a result of rad52 mutation.
11. Rad52 mutated strains grow slowly than RAD strains.
A. True
B. False
Answer: A
Clarification: Rad52 mutated strains grow more slowly and transform less efficiently than RAD strains and therefore are not ideal hosts for YAC library construction.
12. Rad54-3 allele stabilizes clones containing ____________
A. Plant DNA
B. Viral DNA
A. Human DNA
D. Bacterial DNA
Answer: C
Clarification: Le and Dobson in 1997 showed that the rad54-3 allele significantly stabilizes YAC clones containing human satellite DNA sequences.
13. Which of the following is stimulated by the spheroplasting step of YAC transformation system?
A. Mutations
B. Chimera
A. Endotoxins
D. Promoters
Answer: B
Clarification: The chimera formation results from the yeast’s mitotic recombination system which can be stimulated by the spheroplasting step of standard YAC transformation system.
14. There is a high rate of loss of some YACs during Translation
A. Transcription
B. Mitotic growth
A. Meiosis
D. Promoters
Answer: C
Clarification: Transformation of intact yeast cells is much less recombinogenic. There is also a high rate of loss of YACs during mitotic growth.
15. How can YAC DNA be purified from yeast chromosomes?
A. Gel electrophoresis
B. CHEF
A. Centrifugation
D. PFGE
Answer: D
Clarification: Purifying YAC DNA from yeast chromosomes usually requires separation by pulsed-field electrophoresis.