MCB 150 EXAM 2 QUESTIONS AND
ANSWERS
What is the most common number of codons that specifies a single amino acid? -
Answer-two. Ten amino acids are specified by two codons each
How many amino acids would be encoded in the sequence 5′ AUGUUACGGAAU 3′ by
a non-overlapping and maximally overlapping code? - Answer-4 and 10
What feature of the genetic code makes it possible for a single protein to be encoded by
more than one mRNA sequence? See Section 16.3 - Answer-More than one codon can
specify the same amino acid.
A minimal genetic code requires only 21 codons−one for each amino acid, and one for a
stop signal.
Given this, what advantage might be offered by having a code with 64 codons? -
Answer-An advantage of having more than the minimum number of codons is error
tolerance. Because of the redundancy in an expanded code, not every base pair
change will change the meaning of a codon.
A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the
following sequences in the coding strand of the DNA could code for this peptide?
5' ACT-TAC-CAT-AAA-CAT-TAC-UGA
5' GGG-AAA-TTT-AAA-CCC-ACT-GGG
3' AUG-AAA-GGG-TTT-CCC-AAA-GGG
3' UUU-CCC-AAA-GGG-UUU-CCC
5' TTT-CCC-AAA-GGG-TTT-CCC - Answer-TTT-CCC-AAA-GGG-TTT-CCC
Each codon shown below specifies an amino acid. For which one is it possible that a
change in a single base could create a stop codon?
CAC
ACA
AAA
ACC - Answer-AAA
With respect to RNA processing, which of the following is false?
It leads to the production of alternative gene products.
Some introns are removed by spliceosomes.
Some introns are self-splicing.
Prokaryotic mRNAs are polyadenylated at the 3' end.
Chemical modification occurs with tRNA transcripts. - Answer-Prokaryotic mRNAs are
polyadenylated at the 3' end.
ANSWERS
What is the most common number of codons that specifies a single amino acid? -
Answer-two. Ten amino acids are specified by two codons each
How many amino acids would be encoded in the sequence 5′ AUGUUACGGAAU 3′ by
a non-overlapping and maximally overlapping code? - Answer-4 and 10
What feature of the genetic code makes it possible for a single protein to be encoded by
more than one mRNA sequence? See Section 16.3 - Answer-More than one codon can
specify the same amino acid.
A minimal genetic code requires only 21 codons−one for each amino acid, and one for a
stop signal.
Given this, what advantage might be offered by having a code with 64 codons? -
Answer-An advantage of having more than the minimum number of codons is error
tolerance. Because of the redundancy in an expanded code, not every base pair
change will change the meaning of a codon.
A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the
following sequences in the coding strand of the DNA could code for this peptide?
5' ACT-TAC-CAT-AAA-CAT-TAC-UGA
5' GGG-AAA-TTT-AAA-CCC-ACT-GGG
3' AUG-AAA-GGG-TTT-CCC-AAA-GGG
3' UUU-CCC-AAA-GGG-UUU-CCC
5' TTT-CCC-AAA-GGG-TTT-CCC - Answer-TTT-CCC-AAA-GGG-TTT-CCC
Each codon shown below specifies an amino acid. For which one is it possible that a
change in a single base could create a stop codon?
CAC
ACA
AAA
ACC - Answer-AAA
With respect to RNA processing, which of the following is false?
It leads to the production of alternative gene products.
Some introns are removed by spliceosomes.
Some introns are self-splicing.
Prokaryotic mRNAs are polyadenylated at the 3' end.
Chemical modification occurs with tRNA transcripts. - Answer-Prokaryotic mRNAs are
polyadenylated at the 3' end.
