Question.
Certain human conditions result from changes in the DNA sequence. The following is a segment of the template strand of an open reading frame of a functional gene.
3′ . . . GTT CAT CTA ACC CCT GAG GAG . . . 5′
(a) Using the segment shown above, determine the sequence of the corresponding mRNA sequence. Indicate the 5′ and 3′ ends.
(b) Using the table provided, determine the amino acid sequence of the polypeptide fragment.
(c) The mutation results in the following sequence:
3′ . . . GTT CAT CTA ACC CCT GTG GAG . . . 5′
Determine the change in the primary structure of the protein due to this mutation, and explain how this change may lead to a change in the function of the protein.
(d) Describe ONE common human genetic condition that is caused by this type of mutation, including the effect of the change in protein function on the health of the affected individual.
(e) Describe TWO techniques that can be used to identify the presence of this type of genetic change.
▶️Answer/Explanation
Certain human conditions result from changes in the DNA sequence. The following is a segment of the template strand of an open reading frame of a functional gene.
3′ . . . GTT CAT CTA ACC CCT GAG GAG . . . 5′
(a) Using the segment shown above, determine the sequence of the corresponding mRNA sequence. Indicate the 5′ and 3′ ends. (2 points maximum: 1 point for correct sequence with a maximum of one error; 1 point for proper orientation of the 5′ and 3′ ends)
5′ . . . CAA GUA GAU UGG GGA CUC CUC . . . 3′
(b) Using the table provided, determine the amino acid sequence of the polypeptide fragment. (2 points for
correct sequence; only 1 point if sequence contains an error)
gln – val – asp – trp – gly – his – leu
Changed AA may lead to a change in the structure of the protein. Possible elaboration points:
• Change is in the folding into the tertiary or quaternary structure.
• Some AA side groups are more important than others, e.g., cysteine forms disulfide bridges.
• Some AA can be interchanged with no effect on the structure due to lack of interactive side groups.
• Change to enzyme’s active or allosteric site is especially damaging.
• Others as appropriate.
(d)
Common conditions include:
• Tay-sachs
• Sickle-cell anemia
• Increased cancer risk (P53 gene)
• Cystic fibrosis
• Hemophilia
• Others as appropriate
(e)
Techniques include:
• Microarray assays to compare novel and mutant DNA
• DNA sequencing
• RFLP markers
• Presence of diagnostic phenotype
• Specific marker for mutated sequence
• Others as appropriate (Note: VNTR and Karyotyping are not appropriate techniques.)
Question.
Certain human conditions result from changes in the DNA sequence. The following is a segment of the template strand of an open reading frame of a functional gene.
3′ . . . GTT CAT CTA ACC CCT GAG GAG . . . 5′
(a) Using the segment shown above, determine the sequence of the corresponding mRNA sequence. Indicate the 5′ and 3′ ends.
(b) Using the table provided, determine the amino acid sequence of the polypeptide fragment.
(c) The mutation results in the following sequence:
3′ . . . GTT CAT CTA ACC CCT GTG GAG . . . 5′
Determine the change in the primary structure of the protein due to this mutation, and explain how this change may lead to a change in the function of the protein.
(d) Describe ONE common human genetic condition that is caused by this type of mutation, including the effect of the change in protein function on the health of the affected individual.
(e) Describe TWO techniques that can be used to identify the presence of this type of genetic change.
▶️Answer/Explanation
Certain human conditions result from changes in the DNA sequence. The following is a segment of the template strand of an open reading frame of a functional gene.
3′ . . . GTT CAT CTA ACC CCT GAG GAG . . . 5′
(a) Using the segment shown above, determine the sequence of the corresponding mRNA sequence. Indicate the 5′ and 3′ ends. (2 points maximum: 1 point for correct sequence with a maximum of one error; 1 point for proper orientation of the 5′ and 3′ ends)
5′ . . . CAA GUA GAU UGG GGA CUC CUC . . . 3′
(b) Using the table provided, determine the amino acid sequence of the polypeptide fragment. (2 points for
correct sequence; only 1 point if sequence contains an error)
gln – val – asp – trp – gly – his – leu
Changed AA may lead to a change in the structure of the protein. Possible elaboration points:
• Change is in the folding into the tertiary or quaternary structure.
• Some AA side groups are more important than others, e.g., cysteine forms disulfide bridges.
• Some AA can be interchanged with no effect on the structure due to lack of interactive side groups.
• Change to enzyme’s active or allosteric site is especially damaging.
• Others as appropriate.
(d)
Common conditions include:
• Tay-sachs
• Sickle-cell anemia
• Increased cancer risk (P53 gene)
• Cystic fibrosis
• Hemophilia
• Others as appropriate
(e)
Techniques include:
• Microarray assays to compare novel and mutant DNA
• DNA sequencing
• RFLP markers
• Presence of diagnostic phenotype
• Specific marker for mutated sequence
• Others as appropriate (Note: VNTR and Karyotyping are not appropriate techniques.)