Question

Thymine in DNA occurs as the result of thymidylate synthase creating _______, which then undergoes _______ to _______, then to _______, and incorporated into D N A by _______. Thymine in tRNA arises ________, by an S-adenosylmethionine-dependent _______ of a ______ residue in RNA.
a. UMP
b. translocation
c. post-translationally
d. dTDP
e. post- transcriptionally
f. hydroxylation
g. DNA synthase
h. phosphorylation
i. methylation
j. GMP
e. CMP

Answer 1

Answer:

Thymine in DNA occurs as the result of thymidylate synthase creating deoxythymidine monophosphate (dTMP), which then undergoes phosphorylation to deoxythymidine diphosphate (dTDP), then to Deoxythymidine triphosphate (dTTP), and incorporated into DNA by the DNA polymerase (DNA pol). Thymine in tRNA arises post-transcriptionally, by S-adenosylmethionine-dependent methylation of a uridine 5'-monophosphate (UMP) residue in RNA.

Explanation:

Thymidylate synthase is an enzyme involved in de novo DNA synthesis. This enzyme (thymidylate synthase) catalyzes the transfer of the one-carbon group from 5,10-methylene-tetrahydrofolate (5,10-CH2-THF) to deoxyuridine monophosphate (dUMP) and subsequent methylation to produce deoxythymidine monophosphate (dTMP), which is then phosphorylated to deoxythymidine triphosphate (dTTP) by kinases and incorporated into DNA. On the other hand, specific tRNA methylases catalyze the methylation of transference RNA (tRNA) by using S-adenosylmethionine as a methyl donor. Since tRNA methylation is a post-transcriptional modification, this chemical reaction is considered an epitranscriptomic modification on the RNA molecule.