Myopia (nearsightedness) and Phenylketonuria (pronouced fee-nill-key-toe-NURR-ee

Question

Myopia (nearsightedness) and Phenylketonuria (pronouced fee-nill-key-toe-NURR-ee-uh) or PKU is an inherited disorder of metabolism that can cause intellectual and developmental disabilities (IDDS) if not treated. Both are inherited as recessive traits occurring on separate chromosome pairs. A man who is normal phenotypically, but a carrier for both traits marries a woman with an identical genotype with respect to these traits. What is the chance that their first child will be myopic? what is the chance that a child will have PKU? what is the chance that a child will inherit both myopia and PKU simultaneously? What is the likelihood that a child will have neither PKU nor myopia?

Explanation / Answer

For myopia (Normal allele - M and  allele for myopia - m)

For PKU (Normal allele - P and  allele for PKU - p)

Parental generation - MmPp X MmPp

Gametes formed - MP, Mp, mP and mp MP, Mp, mP and mp

F2 generation   

9 M-P- (normal) : 3 M-pp (PKU) : 3 mmP- (myopia) : 1 mmpp (PKU, myopia)

The chance that their first child will be born myopic is - 3/16 (mmPP, mmPp and mmPp)

The chance that the child will have PKU is - 3/16 (MMpp, Mmpp and Mmpp)
The chance that the child will inherit both myopic and PKU stimultaneously is - 1/16 (mmpp)

The liklihood that a child will have neither PKU or myopia is - 9/16 (MMPP, MMPp,MmPP, MmPp, MMPp, MmPp, MmPP, MmPp and MmPp )

Male/Female MP Mp mP mp MP MMPP MMPp MmPP MmPp Mp MMPp MMpp MmPp Mmpp mP MmPP MmPp mmPP mmPp mp MmPp Mmpp mmPp mmpp

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