Question

1a.) Explain the Wobble hypothsis.

My answer-> The wobble hypothesis explains why there are more than one codons coding a single amino acid.

b.) How is translation initiated? ( Make sure to include the necessary components, including sequences, in your answer)

my answer -> The small ribosomal subunit binds to the mRNA. The tRNA bearing methionine binds to the start codon. The large ribosomal subunit binds to the small one. The start codon signals the start of translation.

Answer 1

WOBBLE HYPOTHESIS

In simple words, Wobble hypothesis tells us why multiple codons can code for a single amino acid. According to this mechanism, tRNA can recognize more than one codon for a specific amino acid.

This hypothesis states that the base at 5′ end of the anticodon is not spatially confined as the other two bases allowing it to form hydrogen bonds with any of several bases located at the 3′ end of a codon.

This concludes that first two bases of the codon make normal H-bond pairs with the 2nd and 3rd bases of the anticodon. Less stringent rules apply and non-canonical pairing may occur in the remaining positions. There are flexible set of base-pairing rules at the third position of the codon which allows anticodon of a single form of tRNA to pair with more than one triplet in mRNA.

INITIATION OF TRANSLATION (Protein synthesis)

Initiation of protein synthesis involves the assembly of components of translational system before peptide bond formation. These assembly components includes two ribosomal subunits, mRNA, amnioacyl-tRNA, GTP and initiation factors.

There are three initiation factors in prokaryotes – IF-1, IF-2 and IF-3.

There are more than ten initiation factors in eukaryotes.

AUG is the initiating codon recognized by special initiator tRNA. IF-2 in prokaryotes and eIF2-GTP in eukaryotes facilitate the recognition.

Amino acid-charged initiator tRNA enters the ribosomal P site and GTP gets hydrolysed to GDP. Initiator tRNA has N-formylated methionine. Now, the formyl group is added to methionine by the enzyme transformylase. In eukaryotes, non-formylated methionine is carried by initiator tRNA. This N-termimal methione is usually removed the completion of translation.