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Pedigree explanation

Pedigree explanation - they are not affected the other...

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Pedigree explanation The easiest way to determine the genotype of everyone is to work backwards. 1. Genotypes : SS, SA, AA 2. Who has sickle cell anemia (visible in phenotype): Just the individuals that are shaded in black: 6, 7, 8, 11, 14, 15, 16 3. Carriers : Look at the parentage of those who are affected. If the parent’s phenotype shows that they are unaffected, but one or more of their offspring are affected, then the parent must be a carrier. This is true for: 1, 2 (parents of 6, 7, and 8) and 3, 4 (Parents of 11). Because #6 is homozygous recessive (SS) all of her genetic contribution must be the recessive allele, S. Therefore, 12 and 13 must have at least 1 S allele. Because
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Unformatted text preview: they are not affected, the other allele coming from the father (#5) must be A, so they are indeed carriers. 4. Who may or may not have an allele for sickle cell. We are left with 5, 9, and 10. We now know that father #5 has at least one A allele. We are not given any information on his parentage, so he could be AA or AS. Offspring 9 and 10 are not visibly affected. However, as both parents are carriers, 9 and 10 could also have inherited the S allele. As we have no information about their offspring, we must assume that there is a possibility that they have the S allele....
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