1. Which of the following restriction sites are used in a pYAC3 vector?
a) EcoR1, BamHI
b) BamHI, SnaBI
c) SnaBI, EcoR1
d) HindIII, BamHI
Explanation: The yeast artificial chromosome vector is first restricted with a combination of BamHI and SnaBI, cutting the molecule into three fragments.
2. The DNA to be cloned and inserted into the pYAC3 vector must have sticky ends.
a) true
b) false
Explanation: The DNA to be cloned must and inserted into the Pyac3 vector must have blunt ends because SnaBI is a blunt end cutter.
3. Which is the recognition sequence for SnaBI?
a) TACGTA
b) TCAGTA
c) TAAGTA
d) GTATAC
Explanation: SnaBI is a blunt end cutter and hence the gene to be cloned and the vector as well have blunt ends. Recognition sequence is TACGTA.
4. Which technique is used to introduce the artificial chromosome into the host?
a) Protoplast transfusion
b) Shotgun
c) Electroporation
d) Transduction
Explanation: Protoplast transfusion is used to introduce or transfer the artificial chromosome containing the gene of interest, into the host Saccharomyces Cerevisiae.
5. The host yeast strain used for YAC vectors is an auxotrophic mutant for _________
a) TRP1, URA3
b) LACZ, URA3
c) LEU2, URA4
d) LACZ, URA4
Explanation: The yeast strain that is generally used as a host is a double auxotrophic mutant strain, trp1-negative and ura3-negative which is converted to positives by the selectable markers on the artificial chromosome.
6. Which medium is used to check for the growth of transformants?
a) Minimal
b) LB
c) LB Agar
d) Nutrient
Explanation: Minimal medium is generally used to check for the growth of transformants. It contains no added nutrients and hence only transformants would grow.
7. How can the presence of insert DNA in the YAC vector be checked?
a) Insertional inactivation
b) Insertion activation
c) Antibiotic resistance
d) Plaque formation
Explanation: The presence of DNA in the artificial chromosome vector can be checked by the insertional inactivation of SUP4 gene, carried out by a color test.
8. In the insertional inactivation of SUP4, red colonies are recombinants.
a) true
b) false
Explanation: The presence of DNA can be checked by the insertional inactivation of SUP4 genes, carried out by a color test: white colonies are recombinants, red colonies are not.
9. What is the maximum approximate length of the genes that can be cloned using YACs?
a) 100kb
b) 300kb
c) 600kb
d) 1000kb
Explanation: The YAC vectors can be used to clone genes of large sizes, usually around 600 kb but certain mega-YACs can clone genes upto 1000 kb in length.
10. What are the ends of the two arms of YAC vectors composed of ____________
a) TEL sequences
b) Origin
c) Gene of interest
d) SUP4
Explanation: Telomeres are present at the ends of left and right arms of a restricted vector, these arms result from the restriction with endonucleases BamHI and SnaBI.