X-linked inherited diseases occur far more frequently in males because they only have one X chromosome. Females must receive a copy of the gene from both parents to have such a recessive disease. However, they will still be carriers if they receive one copy of the gene. Recessive genes on the X chromosome that cause serious diseases are usually passed from female carriers to their ill sons and carrier daughters. This is because males, who always have the disease and are not just carriers, would have to father a daughter to pass on the gene. This is unlikely because severe genetic diseases often cause death in childhood or early adulthood. Even those males who survive childhood are unlikely to father children because a sickly male will be less likely to find a mate. However, if the disease shows up late in life, or is not severe, he will pass the gene to all of his daughters. He can not pass it to his sons because a male receives his X chromosome from his mother. A mother with one copy of the gene has a 50% chance of passing it to her children of both sexes, but her daughters will just be carriers of the gene unless their father has it, too. -
wikipretty interesting DNA, genes and all. my sis did mention this to me once. i think cos after u get married, couples wld have to do medical check-ups together. maybe to check for aids or i don't know wad. and the doc told them bout the x-linked thingy. maybe that's what's part of what the check up is too. to see the chances of having a affected child. kinda scary actually.
what got me researching into these was becos of the recent news that one of the singaporean actor has Muscular dystrophy. which got me thinking whether that is the same disease as in the story, 'one litre of tears'. apparently its not. the other one is Spinocerebellar atrophy. but both has this hereditary thingy. which got me into the whole DNA thing.
yup. at 4am in the morning. pretty crazy i know. but hey, i learnt something new.
oh boy. life itself is just amazing.
