5. Explain that Guanine residues within DNA molecules play an important role in adopting unusual DNA
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It is known for forming hydrogen bonds with Cytosine during DNA replication and transcription, which helps maintain the double-helical structure of DNA. Show more…
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(a) The most stable tautomeric form of guanine is the lactam form (or cyclic amide, see Section 17.81 ). This is the form normally present in $\mathrm{DNA}$, and, as we have seen, it pairs specifically with cytosine. If guanine tautomerizes (see Section 18.2 ) to the lactim form, it pairs with thymine instead. Write structural formulas showing the hydrogen bonds in this abnormal base pair. CAN'T COPY THE FIGURE (b) Improper base pairings that result from tautomerizations occurring during the process of DNA replication have been suggested as a source of spontaneous mutations. We saw in part (a) that if a tautomerization of guanine occurred at the proper moment, it could lead to the introduction of thymine (instead of cytosine) into its complementary DNA chain. What error would this new DNA chain introduce into its complementary strand during the next replication even if no further tautomerizations take place?
Question: In the DNA structure, a purine molecule always binds with a pyrimidine molecule. How would you expect the structure to differ if Adenine forms base pairing with Guanine and Cytosine forms base pairing with Thymidine? Instead of A-T, G-C; can it be A-G, C-T? Justify your answer within five sentences.
Josee P.
In the DNA structure, a purine molecule always binds with a pyrimidine molecule. How would you expect the structure to differ if Adenine forms base pairing with Guanine and Cytosine forms base pairing with Thymidine? Instead of A-T, G-C; can it be A-G, C-T? Justify your answer within five sentences.
Adi S.
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