SvS Biology 2000 - Year 10:
Trial solutions for genetics.
1. A condition known as Microsoftia is inherited by a single pair of alleles, this means that BOTH males and females have TWO alleles for that trait. Having Microsoftia is a recessive condition, and requires the affected individual to be HOMOZYGOUS for the trait. Use a test cross to explain how a Headmaster can have Microsoftia even if his parents do not have the trait. (show all of your working, set out correctly to indicate Parents, Gametes and F1)
Phenotype Genotype Microsoftia mm Normal MM or Mm P Mm x Mm
Notice that neither parent had the trait.
but both are carriers of it.
gametes M, m x M, mF1 MM, Mm, Mm, mm
25% chance that he had Microsoftia
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S. van Strien