Missense mutations   a create premature stop codons   b cause no change in a gene product   c change the amino acid sequence of a polypeptide   d none of the above

The following image depicts a short stretch of sequence associated with a gene. Which of the following is true?

a. Mycobacteriophage genes occasionally begin with GUG or, even more rarely , UUG (rather than AUG ). Which amino acids corre spond to these codons ? b. Yeast genes occasionally begin with CUG, ACG , or AUC . Which amino acids correspond to these codons ?

Now imagine that a mutation occurred in the second T of the codon below and the T became a G. How would this affect the mRNA and the amino acid for that codon? Old DNA codon Old RNA codon Old amino acid New DNA codon New mRNA codon New amino acid T  T  G     T  G  G       This would be an example of which type of a point mutation?__________________________

Table of the Standard Genetic Code Middle base 5'- C_-3' UCU Ser (S) |UAU Tyr (Y) UCC Ser (S) UAC Tyr (Y) UCA Ser (S) UCG Ser (S)UAG Ter CCU Pro (P) CAU His (H) CCC Pro (P) CCA Pro (P) CAA GIn (Q) CCG Pro (P) CAG GIn (Q) 5'- _U -3' 5'-_A_-3' 5'-_G_-3' 5'-U_-3' UUU Phe (F) 5'-U_-3' UUC Phe (F) 5'-U_-3' |UUA Leu (L) 5'-U_-3' UUG Leu (L) 5'-C_-3' |CUU Leu (L) 5'-C_-3' |CUC Leu (L) 5'-C_-3' CUA Leu (L) 5'-C_ -3' CUG Leu (L) UGU Cys (C) 5'-_U-3' 5'-_C-3' 5'-_A-3' UGG Trp (W) 5'-_G-3' 5'- U-3' 5'-C-3' 5'-_A-3" 5'- G-3' 5'- U-3' 5'-_C-3' 5- А-3' 5'-_G-3' GCU Ala (A) GAU Asp (D) GGU Gly (G) 5'-_U-3' 5'-C-3' GGA Gly (G)5'-_A-3' GGG Gly (G) 5'-_G-3' UGC Cys (C) UGA Ter UAA Ter CGU Arg (R) CGC Arg (R) CGA Arg (R) CGG Arg (R) ACU Thr (T)|AAU Asn (N) AGU Ser (S) AAC Asn (N) AGC Ser (S) AGA Arg (R) AGG Arg (R) CAC His (H) 5'-A_-3' |AUU lle (1) 5'-A_-3' AUC Ile (1) 5'-A_-3' |AUA lle (1) 5'-A_-3' |AUG Met (M) ACG Thr (T) AAG Lys (K) 5'-G_-3' GUU Val (V) 5'-G_-3' GUC Val (V) 5'-G_-3' GUA Val (V)…

Which of the following mutations in the protein-coding region of a gene is more likely to lead to complete loss of function of the encoded protein: an insertion of six nucleotides or a deletion of two nucleotides? Briefly explain your answer.