Why is haemophilia uncommon in females?

Haemophilia is a genetic disorder that involves the absence of blood clotting factors (factor VIII and IX). It is a rare disorder that usually occurs in males compared to females because of the pattern it's inherited. It is an X-linked recessive disorder that appears in a female would need to inherit two copies of the defected gene, one from each parent, and develop haemophilia.

Define the following: Homologous chromosomes.

Homologous chromosomes contain one set of maternal and one set of the paternal chromosomes that pair up with each other inside a cell during fertilization. A homologous pair has approximately the same length, centromere position, and genes with the same corresponding loci. Each pair carries the same genes in the same order, but the alleles for each trait may or may not be the same.

If the mother is a carrier of colour blindness and the father is normal, show the possible genotype and phenotype of the offspring of the next generation with the help of a punnet square.

Colour blindness is a recessive sex-linked trait in which the eye fails to distinguish red and green colours. The gene for normal vision is dominant. Normal allele (X) and recessive allele (X c ) are carried by X chromosome. Hence, in females, colour blindness appears only when both the X chromosomes carry the recessive gene (X c X c ). But in human males, the defect is appeared in the presence of a single recessive gene (X c Y). In the given cross, the female is a carrier of colour blindness (XX c ) and the father is normal (XY). The possible genotype and phenotype of the next generation are as follows.

A woman with blood group O married a man with blood group AB. Show the possible blood groups of the progeny. List the alleles involved in this inheritance.

ABO blood grouping is an example of codominance and multiple allelism. In this, three alleles govern the same character. The allele for blood group A (I A ) and blood group B (I B ) are codominant, hence, the combination of these two produce blood group AB (I A I B ). In the given experiment, the women with blood group O would have genotype I o I o , while a man with blood group AB would have genotype I A I B . When a cross is performed between these two, the possible blood groups of the progeny will be the following: ♂/♀ I A I B I o I A I o I B I o Thus, the possible blood group of progeny would be A (I A I o ) and B (I B I o ). Alleles involved in the inheritance of blood groups in the progeny are: I A , I B , I o