25) Which of the following is incorrectly paired? a) helicase unwinds parental d

Question

25) Which of the following is incorrectly paired? a) helicase unwinds parental double helix at replication forks b) topoisomerase relieves "overwinding" strain ahead of replication forks c) DNA ligase catalyzes the synthesis of new DNA d) telomerase catalyzes the lengthening of telomeres in eukaryotic germ cells e) nuclease - DNA-cutting enzyme 26) What difference(s) is there between a eukaryotic chromosome and a bacterial chromosome? a) Bacterial chromosomes have circular DNA whereas eukaryotic chromosomes have linear DNA b) Bacterial chromosomes have singled-stranded RNA whereas eukaryotic chromosomes have double stranded DNA c) Bacterial chromosomes are associated with a small amount of protein whereas eukaryotic chromosomes are associated d) e) with a large amount of protein All of the above A and C only 27) The DNA of an organism has adenine as 20% of its bases. What percentage would be cytosine? a) 10 b) 20 c) 30 d) 40 28) How is DNA synthesis different on the lagging strand? (Compared to the leading strand) a) The lagging strand requires an RNA primer but the leading strand does not. b) short fragments called Okazaki fragments must join along the lagging strand c) short fragments called Okazaki fragments must join along the leading strand d) on the lagging strand, nucleotides are added to the 5' end

Explanation / Answer

25. C. DNA ligase is used for the joining of the okazaki fragments not for the synthesis of the DNA. DNA polymerase is used for the DNA replication.

26. Both A and C are correct.

27. According to Chargaff's rules, A=20%

A+G=T+C

i.e A is equals to T and G is equals to C

here, A is 20% therefore T also 20%

now Total G+C in Double stranded DNA= G+C= 100-40= 60%

as G=C= Total % of C= 30%

28. The lagging strand requires the RNA primers as compared to the leading strand. DNA polymerase adds nucleotides only on the 3’ primer end of the growing strand.

22. e. Both A and D

Injecting living S cell and injecting heat killed S cells and R cells.

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