Question

Post Lab Questions: X-linked Sex Linked traits follow the same inheritance pattern in humans as they do in fruit flies. From your newly acquired knowledge answer the questions below. 12. A woman is a carrier for hemophilia, if she has children with a 'normal' male what is the chance they will have a daughter with hemophilia? Explain your answer. 13. If this same pair were to have a male child what is the chance that he would have hemophilia? Explain your answer. 14. For a female to be colorblind, what are all of the possible genotypes of her parents? 15. Can a normal (non carrier) female have a colorblind child? Why or Why not?

Answer 1

12. When women who is a carrier for haemophilia marries a normal male none of her daughters will be haemophilic. The reason is that the daughters are inheriting a normal X chromosome from their father and from the mother half of the daughters are inheriting the mutant X chromosome (are carriers of haemophilia) and the other half are inheriting the normal X chromosome (normal females).

Carrier female   X         Normal male

X_hX_H                                       X_HY

Gametes X_{h &}  X_H   X_{H &}  Y

Progeny   X_hX_H;   X_hY;   X_HX_H;   X_HY (carrier female; haemophilic male; normal female, normal male)

13. 50% of their male children will be haemophilic

14. RED GREEN COLOUR BLINDNESS (Daltonism)

· Medically reported by Wilson

· Unable to differentiate red and green colour

· Gene is located in the X chromosome.

· Gene is recessive

Protanope(red blind), Deuteranope (green blind); Tritanope (blue blind)

Genotype:    Normal male          - X^CY

                        Colour blind male - X_cY

                        Normal female       - X^CX^C

                        Carrier female   - X_cX^C (heterozygous)

                        Colour blind female – X_cX_c

A female can be color blind when her father is color blind and mother is either color blind or a carrier. The possible genotypes of a color blind women will be

Father - X_cY

Mother - X_cX_c or X_cX^C (heterozygous).

15. A normal (non carrier) female cannot have a color blind child. Even if she marries a color blind man none of her children will be color blind. Her daughters will be carriers and sons will be normal. Her daughters are inheriting the normal X chromosomes from their mother. If their father is color blind they inherit the mutant X_c chromosomes from their father. So they have one normal allele and one mutant allele in their genome (X^CX_c) and therefore they are phenotypically normal but carriers. Her sons are inheriting the Y chromosomes from their father and the wild type X chromosome from their mother and therefore are normal.