Haemophilia is a sex-linked inheritance condition in humans where a simple cut causes non-stop bleeding. Study the pedigree chart showing the inheritance of haemophilia in a family. Give reasons, which explain that haemophilia is (i) sex-linked, (ii) caused by X-linked gene.
(i) Haemophilia is sex-linked because:
(a) It is transmitted from an unaffected carrier female to some of the male offsprings.
(b) Female rarely becomes haemophilic as her mother.
has to be atleast a carrier and father should be haemophilic.
(ii) Gene for haemophilia is present on X-chromosome because the heterozygous female for haemophilia may transmit the disease to sons.