1. If you started with one double stranded DNA template, how many PCR cycles wou
ID: 59009 • Letter: 1
Question
1.If you started with one double stranded DNA template, how many PCR cycles would it take to produce 256 double stranded copies:
9 cycles
5 cycles
6 cycles
8 cycles
7 cycles
2.The use of recombinant DNA technology to introduce a gene isolated from one species into another species is called?
Transgenics
Deletion mutagenesis
Gene replacement
Gene knockout
Site-directed mutagenesis
3.If homologous recombination has occurred when generating transgenic mice then the thymidine kinase gene should not be incorporated into the genome of the modified embryonic stem cells.
True
False
4.The value of the beta-galactosidase gene in cloning could best be described as:
The gene encodes a special DNA ligase enzyme.
The gene "reports" if a recombinant product is formed.
The gene provides valuable restriction enzyme cut sites.
The gene confers resistance to antibiotics.
The gene facilitates easier transfer of the DNA into bacterial cells.
5.You wish to probe a human cDNA library to find out which insert has the -globin gene. Which of the following would be a good choice as your probe (assume in all cases your probe is labeled)?
A 60 nucleotide probe corresponding to a -globin promoter sequence.
A 60 nucleotide probe corresponding to exon 1 for -globin.
A 60 nucleotide probe corresponding to intron 1 for -globin.
6.Taq DNA polymerase copies the sequence of mRNA into the first strand of DNA.
True
False
A.9 cycles
B.5 cycles
C.6 cycles
D.8 cycles
E.7 cycles
Explanation / Answer
1. The amplified products in each cycle of PCR grow exponentially except for cycles below 30.
The number of amplified products = 2n, where n is number of cycles
So, in order to get 256 double stranded copies, it would take 8 cycles.
2. (A) Transgenics
3. True
Thymidine kinase is used as a negative selection marker in transgenics. The gene is outside the homologous recombination sequence flanking the engineered construct. When the gene of interest gets incooperated into genome, only thing that happens is the resulting knockout gene comes in place of engineered construct.
4. (C) The gene provides valuable restriction enzyme cut sites.
Beta galactosidase is used as a selectable marker to distinguish recombinant bacterial cells from parental. A gene os interest is cloned at a unique restriction site in beta galactosidase gene which in turn disrupts its function. The recombinants are visually selected by analyzing blue white colonies of bacterial cells. The parental retain the activity of beta galactosidase gene nad produce blue colonies on X-gal (substrate) while recombinants are white due to disruption of beta galactosidase gene which can't act on X-gal.
5. (B) A 60 nucleotide probe corresponding to exon 1 for -globin.
cDNA libraries are produced from processed mRNA which obviously does not contain introns. On the other hand sequence of promoter generally remains conserved within species.
6. False. Taq is a DNA polymerase. Reverse transcriptase copies the sequence of mRNA into cDNA.
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