Question

5. What is the function of RNA polymerase? What might happen if it malfunctions?

6. How is mRNA ‘read’ to generate amino acid sequences, what is the term for this?

7. What is definition of transcription and what is the definition of translation?

8. What are codons and anticodons? What are their functions? What is the genetic code

and what is it’s main function?

Answer 1

Answer 5:

RNA polymerase catalyzes the synthesis of RNA from a DNA template. RNA polymerase catalyzes the initiation and elongation of RNA chains. The reaction catalyzes by this enzyme is:

(RNA)_n + ribonucleoside triphosphate <--------------> (RNA)_n+1 + PP_i

All three types of cellular RNA that is mRNA, tRNA, rRNA are synthesized in E.Coli by the same RNA polymerase. However in mammalian cell several different types of RNA polymerase takes part in synthesis.

Answer 6:

This process is known as translation.

Messenger RNA ( mRNA) is the template for protein synthesis, or translation. In eukaryotes, mRNA has structural features such as step-loop structure, that regulates the efficiency of translation and lifetime of the mRNA.

Answer 7:

The synthesis of RNA from a DNA template is called transcription and is catalyzed by the enzyme RNA Polymerase.

Process by which mRNA directs protein synthesis with the assistance of tRNA is called translation.

Answer 8:

Codon:

A codon is a triplet of a nucleotide that codes for a specific amino acid for example AUG ( initiation codon), UAA, UAG, UGA ( Stop codon).

Translation occurs in such a way that these codons are read in a successive and overlapping fashion.

Several codons serve several functions. The initiation codon, AUG, signals the beginning of a protein in all cells. Three of the 64 possible codon, do not code for any known amino acid, these are termed as termination codons. Termination or stop codon signals the end of protein synthesis.

Anticodons:

Transfer RNA's base pairs with mRNA codons by means of a three base sequence on tRNA called the anticodon. The first base of the codon in mRNA ( 5'---->3') pairs with the third base of the anticodon.

The function of anticodons is to bring together the correct amino acids to create a protein, based on the instructions carried in mRNA.

Genetic Code:

The genetic code is the relation between the sequence of bases in DNA and the sequence of amino acid in proteins. Key features of genetic code are:

a: Three nucleotide ( Codons) encodes an amino acid.

b: The code is non overlapping.

c: The genetic code is degenerate that is most amino acids are encoded by more than one codon.

If the genetic code were not degenerate, 20 codons would designate amino acids ( Because there are 20 amino acids) and 44 would lead to chain termination. The probability of mutating to chain termination would therefore be much higher with a degenerate code. Thus, degeneracy minimizes the deleterious effect of mutation.