1. The piece of RNA below includes the region that codes for the binding site for the initiator tRNA needed in translation.

5?-GUUUCCCGUAUACAUGCGUGCCGGGGGC-3?

Which amino acid will be on the tRNA that is the first to bind to the A site of the ribosome?

(a) Methionine

(b) Arginine

(c) Cysteine

(d) Valine

2. In a haploid organism, the DNA encoding one of the tRNAs for the amino acid tyrosine is

mutated such that the sequence of the anticodon is now 5?-CTA-3? instead of 5?-GTA-3?. Protein

synthesis takes place but the proteins produced are abnormal. Some of the proteins produced

contained extra amino acids, while others contained fewer amino acids than normal.

Explain why some proteins contained extra amino acids [1] while others contained fewer amino

acids than normal. [1]

U A G U UUU Phe (F) UUC. UUA Leu (L) UUG. CUU Leu (L) CUC. CUA. CUG AUU lle (1) AUC. AUA. AUG Met (M) GUU Val (V) GUC. GUA. GUG The Genetic Code A UCU Ser (S) UAU Tyr (Y) UAC. UCC - UCA. UCG UAA Stop UAG Stop CCU Pro (P) CAU His (H) CCC - CAC CCA. CCG- ACU Thr (T) AAU Asn (N) ACC - AAC. ACA. ACG GCU Ala (A) GAU Asp (D) GCC. GAC . GAA Glu (E) . GAG GCA GCG CAA Gin (Q) CAG AAA Lys (K) AAG G UGU Cys (C) UGC. UGA Stop UGG Trp (W) CGU Arg (R) CGC - CGA. CGG AGU Ser (S) AGC. AGA Arg (R) AGG. GGU Gly (G) GGC. GGA. GGG