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1) Hemophilia is an impairment of blood clotting that is heritable. Parents that

ID: 19134 • Letter: 1

Question

1) Hemophilia is an impairment of blood clotting that is heritable. Parents that do not show signs of impairment have a son who expresses the hemophilia phenotype. Simultaneously, he also shows the Klinefelter syndrome.
How can you explain the simultaneous occurrence of Klinefelter syndrome and the x-linked recessive hemophilia? Please include in your answer the abnormal chromosomal behavior at meiosis.
Can you tell whether the recessive allele(s) originated from the father or from the mother? Please explain why!
Can you tell at what stage of meiosis the abnormal chromosomal behavior occurred? Please explain why!

Explanation / Answer

HEMOPHILA ALLELE---------XC

Mother is carrier -------GENOTYPE -----XXC

BECAUSE OF NON DISJUNTION IN MOTHER DURING OGENEIS         AT M1 STAGE

–LEAD TO FORMATION OF

OVA-----------XXC

AND NULLISOMIC OVA


FATHER ---------GENOTYPE -----------XY

OVA-----------XXC    FUSES WITH NORMAL SPERM CARRYING Y CHROMOSOME

RESULTS IN Klinefelter syndrome WITH hemophilia phenotype.