Exam 2 MB2
A mutation in the DNA sequence of a gene results in the start codon of a gene being altered.
Which of the following outcomes is a reasonable prediction? - ANS-- mRNAs generated by
expression of the gene might not be translated.
***A start codon is necessary to indicate where translation should start and is important for
positioning a ribosome on an mRNA in the first step of translation. Without a start codon, the
most likely result is that the polypeptide will not be produced. If another AUG codon was
present in the mRNA, and translation was able to start at the other AUG, the first amino acid
would still be Met and the polypeptide would be shorter.
Alterations in the start (or stop) signal for translation do NOT affect transcription of a gene.
\A nucleotide is inserted in the middle of the coding region of a gene. What are the potential
effects on the polypeptide produced by expression of the gene? - ANS-The insertion has the
potential to alter only amino acids specified by codons after the inserted nucleotide, and
could change the length of the polypeptide chain.
\During transcription, RNA polymerase incorrectly adds a G instead of an A in the strand it is
forming. This mistake changes a codon that normally corresponds to Thr to a codon that
corresponds to Ala. What effect will this mistake have in a cell? - ANS-- Multiple protein
molecules in a cell will have Ala instead of Thr at one position in the polypeptide chain
because the mRNA will be translated multiple times.
***Transcription is the process that uses a DNA template to generate an mRNA. Altering a
nucleotide in an mRNA can ONLY affect polypeptides produced by translation of that
particular mRNA. An individual mRNA is translated more than once, so multiple polypeptides
will be affected. Mistakes that occur during transcription do NOT affect the DNA sequence of
a gene, and thus will not affect other mRNAs generated by expression of the gene.
\Part complete
Select ALL statements below that correctly describe BOTH DNA replication and
transcription. - ANS-- new strands are formed in a specific direction
- process requires a template DNA strand
- a polymerase enzyme forms a complementary strand
- a specific DNA sequence indicates start
\Select ALL statements that correctly describe splicing.
- Splicing involves removing DNA sequences from genes that are not required for
translation.
- Splicing occurs in both prokaryotic and eukaryotic cells.
- Splicing takes place after both transcription and translation has occurred.
A mutation in the DNA sequence of a gene results in the start codon of a gene being altered.
Which of the following outcomes is a reasonable prediction? - ANS-- mRNAs generated by
expression of the gene might not be translated.
***A start codon is necessary to indicate where translation should start and is important for
positioning a ribosome on an mRNA in the first step of translation. Without a start codon, the
most likely result is that the polypeptide will not be produced. If another AUG codon was
present in the mRNA, and translation was able to start at the other AUG, the first amino acid
would still be Met and the polypeptide would be shorter.
Alterations in the start (or stop) signal for translation do NOT affect transcription of a gene.
\A nucleotide is inserted in the middle of the coding region of a gene. What are the potential
effects on the polypeptide produced by expression of the gene? - ANS-The insertion has the
potential to alter only amino acids specified by codons after the inserted nucleotide, and
could change the length of the polypeptide chain.
\During transcription, RNA polymerase incorrectly adds a G instead of an A in the strand it is
forming. This mistake changes a codon that normally corresponds to Thr to a codon that
corresponds to Ala. What effect will this mistake have in a cell? - ANS-- Multiple protein
molecules in a cell will have Ala instead of Thr at one position in the polypeptide chain
because the mRNA will be translated multiple times.
***Transcription is the process that uses a DNA template to generate an mRNA. Altering a
nucleotide in an mRNA can ONLY affect polypeptides produced by translation of that
particular mRNA. An individual mRNA is translated more than once, so multiple polypeptides
will be affected. Mistakes that occur during transcription do NOT affect the DNA sequence of
a gene, and thus will not affect other mRNAs generated by expression of the gene.
\Part complete
Select ALL statements below that correctly describe BOTH DNA replication and
transcription. - ANS-- new strands are formed in a specific direction
- process requires a template DNA strand
- a polymerase enzyme forms a complementary strand
- a specific DNA sequence indicates start
\Select ALL statements that correctly describe splicing.
- Splicing involves removing DNA sequences from genes that are not required for
translation.
- Splicing occurs in both prokaryotic and eukaryotic cells.
- Splicing takes place after both transcription and translation has occurred.
