i dont know why but i always get these type of questions wrong so can someone explain how to actually interpret diagrams like this??
thanks so much!
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From the stimulus, the mum and dad are heterozygous, meaning they are both rR (r recessive R dominant). From this we can infer that one of the bands represents the recessive allele (r) and the other represents the dominant allele (R).
The parents have two unaffected children, therefore, one of Child 1 and Child 2 is homozygous dominant, and the other is heterozygous. Therefore, from looking at the bands present, Child 1 is homozygous dominant (with the bottom band being R) and Child 2 is heterozygous. Therefore Child 3 is homozygous recessive (only having the top band present), and therefore because sickle cell anaemia is a recessive disease, Child 3 will have the disease.
