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A2 biology genetics question

quirksy

Not quite sure how to go about answering this question..any help appreciated!

Thanks in advance.

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Reply 2

Teen_titans2702

As u can see, the allele A makes a functional enzyme A that converts the precursor to the intermediate substance. If it aa, which means the functional enzyme A is no longer produced, so the precursor cannot be converted to the intermediate, which means, there is no substrate for enzyme B to convert into the purple pigment => thats why the flower appears white!

Reply 3

Harantony

Homozygous for the recessive, mutant, allele means having aa as a genotype. Because at least one A allele is needed to produce enzyme A for the first reaction to occur, the enzyme will not be synthesised from the allele. This means that the substrate, the white precursor substance, won't be able to form the intermediate substance. Regardless whether they have B or not, if the intermediate isn't produced, you're never going to have purple flowers. :smile: