49. Tautomerization of nucleotides A) is important as a cause of errors in DNA r
ID: 100868 • Letter: 4
Question
49. Tautomerization of nucleotides
A) is important as a cause of errors in DNA replication
B) is important as a cause of errors in transcription
C) is important in formation of the wobble pairs important in protein translation
D) is irreversible process
E) does not lead to formation of isomers
50. __ promotes the formation of covalent bonds between ____ thymine residues in a DNA strand creating a ____ ring called a thymidine dimer.
A) Visible light; adjacent; cyclohexyl
B) Visible light; nearby; cyclobutyl
C) UV light; adjacent; cyclobutyl
D) UV light; nearby; cyclohexyl
E) IR light; adjacent; cyclobutyl
51. The ____strand has the same nucleotide sequence and direction as that of the RNA transcript, with the ____ end of mRNA encoding the N-terminus of the protein.
A) template; 3'
B) template; 5'
C) nontemplate; 3'
D) nontemplate; 5'
E) lagging; 5'
Explanation / Answer
Answer=
49. Tautomerization of nucleotides
A) is important as a cause of errors in DNA replication
Explanation= Each of the common base in DNA can spontaneously undergo a trasient rearrangement of bonding.
A proton shift in nitrogenous base forms one of its rare tautomeric form .called as tautomeric shift .
Formation of the tautomer of any base alters its base pairing properties.
The more stable keto forms of thymine &guanine & amino forms of adenine & cytosine may infrequently undergoes tautomeric shift to less stable enol & imino forms .
The bases would be expected to exist in their less stable tautomeric forms for very short period of time .
however ,if a base existed in the rare form at that of moment that it was being replicated or being incorporated into a nascent DNA chain, a mutation might result.
Incorrect options are =
B) is important as a cause of errors in transcription
C) is important in formation of the wobble pairs important in protein translation
D) is irreversible process - it is reversible process hence it is wrong option
E) does not lead to formation of isomers- it leads to formation of ismers hence it is incorrect option .
Answer=
50.UV light promotes the formation of covalent bonds between Adjacent thymine residues in a DNA strand creating a Cyclobutyl ring called a thymidine dimer.
Correct option =
C) UV light; adjacent; cyclobutyl
Explanation = UV radiation acts as potent physical mutagen & generates a number of photoproducts of DNA .
UV radiation of 260 nm induces dimerization of adjacent pyrimidine bases,especially if these are both thymines ,resulting in a cyclobutyl dimer .
Answer=51]
The Nontemplate strand has the same nucleotide sequence and direction as that of the RNA transcript, with the 5, end of mRNA encoding the N-terminus of the protein.
D) nontemplate; 5'
explanation - The Nontemplate strand has the same nucleotide sequence and direction as that of the RNA transcript
it is a strand which contains codons .
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