There is a tRNA with anticodon UAC. If we apply the wobble hypothesis, then this tRNA can decode which of these codons?
1) It can decode AUG, AUC, AUU, AUA
2) It can decode AUG and AUC but not AUU and AUA
3) It can decode AUG but not AUC, AUU and AUA
4) It cannot decode any one of these codons AUG, AUC, AUU and AUA
Answers
Answer:
The Genetic Code
How do 64 different codons produce 20 different amino acids?
The start codon is AUG. Methionine is the only amino acid specified by just one codon, AUG.
The stop codons are UAA, UAG, and UGA. They encode no amino acid. The ribosome pauses and falls off the mRNA.
The stretch of codons between AUG and a stop codon is called an open reading frame (ORF). Computer analysis of DNA sequence can predict the existence of genes based on ORFs.
Other amino acids are specified by more than one codon--usually differing at only the third position.
The "Wobble Hypothesis,"discovered by Frances Crick, states that rules of base pairing are relaxed at the third position, so that a base can pair with more than one complementary base. Some tRNA anticodons have Inosine at the third position. Inosine can pair with U, C, or A. This means that we don't need 61 different tRNA molecules, only half as many.
Evolution of the Code
Did codons evolve to correspond to particular amino acids based on chemistry, or did the code evolve at random?
The code evolved at random, in that there is no direct chemical connection between, say, GGG and Glycine. BUT--the code appears to have evolved along certain lines for logical reasons. The two most "fundamental" amino acids are Gly and Ala, in biochemical pathways and in natural occurence in prebiotic systems. Both are specified by G/C pairing at the first two positions--the strongest possible interaction. Early life, under high-heat conditions, would have needed extra strong codon-anticodon pairing. The first code may even have been a two-base code
Explanation:
Protein translation
Translation involves the conversion of a four base code (ATCG) into twenty different amino acids. A codon or triplet of bases specifies a given amino acid. Most amino acids are specified by more than one codon.
The conversion of codon information into proteins is conducted by transfer RNA. Each transfer RNA (tRNA) has an anticodon which can base pair with a codon. Some anti-codons have modified bases that can pair with more than one codon, specifying the same amino acid; this means that we don't need 61 different tRNA molecules for all 61 codons. (What do the other three codons specify?)
.
:
Answer: option 1
Explanation: