For the following pedigrees propose the most likely genetic

For the following pedigrees, propose the most likely genetic mechanism underlying the observed inheritance pattern. In other words, is it autosomal or sex-linked and is it dominant or recessive. Based on your answer, indicate the most likely genotype for the individual indicated by the arrow. Please use the blanks provided near each arrow. Do not assume there is one of each.

Solution

a. In this pedigree, since, the trait is not expressed in all generations we have to assume it is due to a recessive gene. In this case the gene appears to be autosomal, because neither of the sons of the affected lady have inherited the trait. Consanguinous marriage has been indicated in third generation, and this is why after two generations, did not inherit the gene, it was expressed in the 4th generation. Assuming the normal alleles of this gene as B and the recessive alelle which is causing the particular inheritance as b, the most probable genotype of the individual indicated by arrow should be Bb.

b.In this pedigree, since, the trait is not expressed in all generations we have to assume it is due to a recessive gene. In this case the gene appears to be autosomal, because the usual pattern of sex-linked inheritance is not observed. Assuming the normal alleles of this gene as B and the recessive alelle which is causing the particular inheritance as b, the most probable genotype of the individual indicated by arrow should be bb.

c. This inheritance pattern could be explained as X-linked recessive, since only, the daughter, of the affected male has seems to be carrier for the trait. The most probable genotype of the individual indicated by arrow should be X^aX(assuming the X chromosome, which she has inherited fro her father to be X^a and X represents the normal X chromosome).

d. This could be explained by autosomal dominant pattern of inheritance. Assuming the dominant allele of this gene as B and the recessive alelle b, the most probable genotype of the individual indicated by arrow should be bb.