Predicted Sex Ratio of Children with Lethal Sex-Linked Gene?

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SUMMARY

The discussion centers on predicting the sex ratio of children from a couple where the male has a normal X chromosome (XDY) and the female is heterozygous for a lethal recessive allele (XDXd). The Punnett square analysis reveals that the couple can produce 100% normal female offspring (XD XD, XD Xd) and a 50% chance of normal male (XD Y) and a 50% chance of lethal male (Xd Y). Therefore, the predicted sex ratio of the offspring is 2:1 female to male, as lethal males do not survive.

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  • Understanding of basic genetics, specifically sex-linked inheritance
  • Familiarity with Punnett squares for predicting genetic outcomes
  • Knowledge of dominant and recessive alleles
  • Concept of lethal alleles and their impact on offspring viability
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7. Hand in question: Suppose that an allele, d, of a sex-linked gene is recessive and lethal. A man marries a woman who is heterozygous for this gene. If the couple had many normal children, what would be the predicted sex ratio of these children?

Female: XDXd

Male: XDY

Punette sqaure:

XD Xd
XD XD XD XD Xd
Y XD Y Xd Y

1: XD XD : 1 XD Xd : 1 XD Y : 1Xd Y

XD XD , XD Xd : 100% normal female

XD Y , Xd Y : 50% normal male, 50% letal
 
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So far your work looks fine, but they're asking for the sex ratio, which means the ratio of male:female offspring (or female:male, it doesn't matter which way you represent it, as long as you specify). You have all the information you need to find this based on the work you've already done.
 

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