In children that express recessive genetic diseases , it has been occasionally f

Question

In children that express recessive genetic diseases, it has been occasionally found that only one parent is heterozygous for the disease allele. In these cases, it has also been confirmed that the parents are the true biological parents of the affected child. Which explanation best accounts for this if the mother is the carrier? Select all possibilities.

Mother’s normal egg is fertilized by a sperm that went through nondisjunction in Meiosis II

Mother’s egg went through nondisjunction in meiosis II and is fertilized by sperm that went through nondisjunction in meiosis I

Mother’s egg went through nondisjunction in meiosis II and is fertilized by sperm that went through nondisjunction in meiosis II

Mother’s egg that went through nondisjunction in Meiosis II and is fertilized by father’s normal sperm

Mother’s normal egg is fertilized by a sperm that went through nondisjunction in Meiosis I

Mother’s egg that went through nondisjunction in Meiosis I and is fertilized by father’s normal sperm

Mother’s egg went through nondisjunction in meiosis I and is fertilized by sperm that went through nondisjunction in meiosis I

Mother’s egg went through nondisjunction in meiosis I and is fertilized by sperm that went through nondisjunction in meiosis II

can you please show me how you did this?

Mother’s normal egg is fertilized by a sperm that went through nondisjunction in Meiosis II

Mother’s egg went through nondisjunction in meiosis II and is fertilized by sperm that went through nondisjunction in meiosis I

Mother’s egg went through nondisjunction in meiosis II and is fertilized by sperm that went through nondisjunction in meiosis II

Mother’s egg that went through nondisjunction in Meiosis II and is fertilized by father’s normal sperm

Mother’s normal egg is fertilized by a sperm that went through nondisjunction in Meiosis I

Mother’s egg that went through nondisjunction in Meiosis I and is fertilized by father’s normal sperm

Mother’s egg went through nondisjunction in meiosis I and is fertilized by sperm that went through nondisjunction in meiosis I

Mother’s egg went through nondisjunction in meiosis I and is fertilized by sperm that went through nondisjunction in meiosis II

Explanation / Answer

In nondisjunction, the chromosomes do not separate correctly which results in the gametes formed with few chromosomes. When nondisjunction occurs in meiosis, it will result in all gametes having aneuploidy (failure of homologous chromosomes to separate) while if it occurs in Meiosis II, it will result in 50% of gametes having aneuploidy. So in this case, the mother's egg would have gone through nondisjunction in Meiosis I or II (only one parent is heterozygous for the diseased recessive allele) and the father is unaffected.

So the possible options would be:

Mother’s egg that went through nondisjunction in Meiosis II and is fertilized by father’s normal sperm

Mother’s egg that went through nondisjunction in Meiosis I and is fertilized by father’s normal sperm.

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