Tay Sach's disease is a genetic condition that can be caused by mutations in the hexosaminidase gene resulting in an abnormal enzyme - VCE - SSCE Biology - Question 13 - 2009 - Paper 1
Question 13
Tay Sach's disease is a genetic condition that can be caused by mutations in the hexosaminidase gene resulting in an abnormal enzyme.
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Worked Solution & Example Answer:Tay Sach's disease is a genetic condition that can be caused by mutations in the hexosaminidase gene resulting in an abnormal enzyme - VCE - SSCE Biology - Question 13 - 2009 - Paper 1
Step 1
A. a substitution of G for C at the beginning of codon 7.
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Answer
This substitution would not create the observed abnormal hexosaminidase as the normal codon at position 7 is 'GUU' and the abnormal is also 'GUU'. Therefore, this change does not affect the enzyme's function.
Step 2
B. a duplication of ACU at the beginning of codon 4.
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Duplicating 'ACU' would not directly result in the amino acid change required for the abnormal enzyme since it would create a situation where an extra threonine is inserted, rather than changing the codon itself.
Step 3
C. an insertion of UAC at the beginning of codon 5.
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Inserting 'UAC' at codon 5 would alter the amino acid from serine to tyrosine, which is consistent with the observed change in the abnormal enzyme. This option is plausible.
Step 4
D. deletion of UCU at the beginning of codon 6.
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Deleting 'UCU' at codon 6 would impact the translation process and could cause a shift in the subsequent codons, potentially leading to a frameshift and a completely different sequence downstream. This could feasibly result in an abnormal enzyme.
