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Phenylketonuria (PKU) is an example of a genetic disorder which affects the following metabolic pathway - Scottish Highers Human Biology - Question 2 - 2017
Question 2
Phenylketonuria (PKU) is an example of a genetic disorder which affects the following metabolic pathway. dietary protein amino acid phenylalanine enzyme 1 ami... show full transcript
Worked Solution & Example Answer:Phenylketonuria (PKU) is an example of a genetic disorder which affects the following metabolic pathway - Scottish Highers Human Biology - Question 2 - 2017
Step 1
Describe how a substitution mutation would alter the gene coding for enzyme 1.
Answer
A substitution mutation involves replacing one nucleotide or base in the DNA sequence with another. This change can result in the alteration of a single amino acid in the enzyme's polypeptide chain. Depending on the nature of the substitution, the enzyme may still function normally, have reduced activity, or become completely nonfunctional.
Step 2
Explain how a substitution mutation may cause the synthesis of a faulty enzyme.
Answer
The substitution mutation can lead to the synthesis of a faulty enzyme by changing the sequence of amino acids that constitute the enzyme's structure. If the amino acid change occurs at a critical position, it may alter the enzyme's active site or overall three-dimensional shape, resulting in an enzyme that cannot appropriately bind to its substrate or perform its catalytic function.
Step 3
why PKU results in a build-up of phenylalanine;
Answer
PKU results in a build-up of phenylalanine because enzyme 1, which is responsible for converting phenylalanine to tyrosine, is faulty due to the genetic mutation. As a result, phenylalanine cannot be effectively broken down, leading to its accumulation in the body.
Step 4
why individuals with PKU can still produce melanin.
Answer
Individuals with PKU can still produce melanin because they can still utilize tyrosine in a separate pathway. Although the conversion of phenylalanine to tyrosine is hindered, any tyrosine obtained from dietary sources can still be converted into melanin.
Step 5
Step 6
Describe how brain damage can be prevented in babies diagnosed with PKU.
Answer
Brain damage can be prevented in babies diagnosed with PKU by implementing a strict, low-phenylalanine diet immediately after diagnosis. This diet limits the intake of phenylalanine, thereby reducing its accumulation and minimizing the risk of neurological damage.
Step 7
Calculate the percentage chance of their next child having this disorder.
Answer
Since both parents are unaffected carriers of the autosomal recessive allele, there is a 25% chance (1 in 4) that their next child will inherit PKU. This can be illustrated using a Punnett square for the combination of the alleles.