Young parents are surprised that they, who have the same Rh factor, have a child with an Rh negative factor

| August 12, 2021 | education

Young parents are surprised that they, who have the same Rh factor, have a child with an Rh negative factor. What was the likelihood of such a child being born in this family? the presence of the Rh factor is a dominant sign.

Let’s designate the gene that causes the development of a positive Rh factor in human blood as R, then the gene for a negative Rh factor will be designated as r.

A child born with a negative Rh factor will have a homozygous rr genotype, because homozygosity is a condition for the realization of a recessive trait in the phenotype. He inherits the recessive gene r from each of the parents, therefore, Rh-positive parents are heterozygous for this trait.

Parents have genotypes Rr and produce two types of eggs and sperm – R and r. From this married couple, offspring are possible, represented by the following options:

homozygote children with a negative Rh factor (rr) – 25%;

heterozygote children with a positive Rh factor (Rr) – 50%;

homozygote children with a positive Rh factor (RR) – 25%.

Answer: 25%.



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