Which direction is the genetic code read on an mRNA? a. 5\' to 3\' b. 3\' to 5\'

Question

Which direction is the genetic code read on an mRNA?

a. 5' to 3'

b. 3' to 5'

c. either direction depending on the protein you want to make

d. because of post-transcriptional processing, mRNA's do not have directionality

RNAs contain four distinct nucleotide bases (A, U, G, C). Three bases code for one amino acid, meaning that there are 64 possible combinations of bases (43). Yet there are only 20 amino acids. Why the excess codons? The excess codons

a. are mostly stop codons

b. are used to indicate which enzymes are needed to make which bonds

c. add redundancy to the code as well as a few stop codons

d. code for specific charges or polarity of the same amino acid

tRNAs possess one of 48 distinct anti-codons, yet there are 61 codons that code for amino acids. How can 48 anti-codons match with 61 codons?

a. certain sets of 3 nucleotides act as “punctuation” indicating when the synthetic machinery should move on to the next amino acid; there is not need to have anti-codons for those sets

b. Through “wobble pairing” – depending on the base, the third nucleotide in the anti-codon to codon pairing doesn’t need to match, allowing for one anti-codon to hybridize to multiple codons

c. Certain combinations of nucleotides never appear, so there are effectively only 48 codons to match with

d. Only the first two nucleotides in a codon to anti-codon pair hybridization matter; the third ones do not interact

Explanation / Answer

Answer 1:- (a) 5'to 3'

Answer2:- (a) are mostly stop codon

Answer 3:- (b) through'wobble pairing' - depending on the base, the third nucleotide in the anticodon to codon pairing doesn't need to match, allowing for one anticodon to hybridize to multiple codon.

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