Question

Question 2 (14 pts) Position 210 in the wild-type, tryptophan synthetase A protein of E. coli is occupied by glycine. The following sequences of amino acid substitutions and restitutions occur at this position: ile ----->arg<----->gly<--->glu A. Show the codons and the one-letter alterations that will account for the changes shown in the amino acids. (A codon chart is provided.) B. Which of the amino acid changes are the results of transitions? Which are the results of transversions? C. Give one cause of a spontaneous transition and one cause of a spontaneous transversion. D. Name one chemical agent for inducing transitions and one chemical agent for inducing transversions.

Answer 1

A. Ile (l) (AUA)...... Arg (R) (CGA)........Glycine (G) (GGA) ------ Glu (E) (GAA)

B. From Glycine (GGA) to Glutamic acid (GAA) , G to A change is Transition

From Glycine (GGA) to Arginine (CGA), G to C change is Transversions.

From Arginine (CGA) to Isoleucine (AUA), C to A & G to U changes are transversions  

C. One cause of spontaneous transition: oxidative deamination or tautomerization

One cause of spontaneous transversions: DNA oxidation

D. Ultraviolet ray can cause induced transitions and Benzopyrine can cause induced transversions.