Answer:
In heart valve disease, one or more of the valves in your heart doesn't work properly. Your heart has four valves that keep blood flowing in the correct direction. In some cases, one or more of the valves don't open or close properly. This can cause the blood flow through your heart to your body to be disrupted.
Sister chromatids have different alleles although carry same genes on same loci. So if it doesn't happen so, like if there are same alleles on sister chromatids then there is a problem in its formation. i.e., male and female alleles haven't contributed equally ( may be an error during their segregation process ). And obviously it doesn't happen in a real cell so we must understand this point. Because normally whenever it happens there's one half from the male and one half from the female. (i.e. maternal and paternal alleles contribute equally).
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