Question

. Metro by T-Mobile LTE 10:40 PM 69% Done 9 of 9 Is coding strand so assume both could be the coding strand 5' - GCTAATGCACOTT - 3 3' - OGATTACGTGCAA - 5 5-CGALUAC GUGCAA - 3 3-GCUAAUGCACGUU - 5 As opposed to DNA replication or transcription, translation requires the correct reading frame. a) Use the sequence below to illustrate what the reading frame" on an mRNA refers to 5' UUGCAYUGSAGC 3' b) Write out ALL of the possible reading frames for the RNA shown in part(a) Leo-His- Cys - Ser 8) During translation, a nucleotide "code" is converted into an amino acid code. Describe or illustrate the physical mechanism for how tRNA enables the cell to interpret the code contained in an mRNA molecule.

#8

Answer 1

Translation is formation of proteins by reading the message present in the mRNA molecule. mRNA brings genetic code in the form of triplet codons. ( AUG, UUG, CAU etc).

Cosidering the AUG, UUG, CAU ....... is the mRNA

mRNA attches to the ribosomes such that the initiation codon is exposed to frst tRNA. Initiation codon is AUG on the mRNA. This codon codes for methionine. The amino acid Methinine to the ribosomes by a tRNA whose anticodon is UAC. AUG and UAC are complimentary to each other. If second codon on the mRNA is UUG, the tRNA with AAC anticodon will bind to the codon. The tRNA with AAC anti codon will carry leucine amino acid. So the second codon brought is leucine. When two tRNA molecules are present on the mRNA which is attached to ribosomes, a peptide bond is formed between the amino acids giving rise to a dipeptide. If the third codon is CAU, a tRNA with anticodon GUA will come and settle as it is complimentary to CAU. tRNA with GUA anti codon will bring valine amino acid to the mRNA molecule. Now the third amino acid brought will be linked to the dipeptide, forming a tripeptide. 4th codon will also be read by the tRNA bringing a specific amino acid based on the codon on the mRNA molecule. This goes on till the stop codon is met. The stop codons are UAG,UGA,UAA. Thse codons are not recognized by tRNA molecule. So tRNA will not settle to these codons. AUG is the start codon on the mRNA molecule.

So this is how the complimentarity of the mRNA and tRNA will help in reading the message present on the mRNA. The nucleotides form hydrogen bonds betwen them. C always is complimentary to G and hence both pairs with G. And A always binds with U because both are complimentary to each other.

This is how the codons are read by tRNA and make a specific protein.