Styles Explain what \"lyonization\" is. When does it occur? How many cells are i

Question

Styles Explain what "lyonization" is. When does it occur? How many cells are in the embryo when it occurs? (Hint: the Wikipedia definition is misleading and just not very good. Use a more reliable medical/biological source please.) Calculate the probability (show your work) that if lyonization first occurs in enbyo, that he restuthn n nemnal a each cell of the 16 cell-stage embryo, that the resulting heterozygous female embryo would exhibit 100% inactivation of the normal allele, and thus would later exhibit the full disease phenotype of hemophilia B: What is the probability that any 1 of the cells in the 16-cell embryo will express the normal allele, while the other 15 cells will inactivate the normal allele? (Show your work.) This kind of outcome would still result in hemophilia for that female. (Hint: use the "factorial" equation from Lab 3) Now add those 2 probability numbers together to get an idea about how rare (and unfortunate) this type of situation is, i.e. for a female to be a "manifesting heterozygote:

Explanation / Answer

1) Lyonization is the mechanism whereby one of the two X chromosomes in females is inactivated. It is a random process that occurs in early embryonic development and hence this is present in every cell of the then formed female foetus. It occurs in the two or four celled embryonic stage

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