Pedigree for determining probability of exhibiting sex linked recessive trait | Khan Academy

TL;DR

This video explains how to calculate the probability of a child being colorblind based on the parents' genotypes.

Transcript

• [Instructor] We are told the pedigree chart represents the inheritance of color blindness through three generations. And we see this here. The standard convention is a square is male, circle is female. If it's colored in, that means that they exhibit the trait, in this case it's color blindness. So Bill exhibits color blindness. His phenotype is ... Read More

Key Insights

• 💹 Pedigree charts are useful for visualizing patterns of inheritance in genetic traits.
• ☺️ Color blindness is an X-linked recessive trait, meaning it is more common in males.
• ❓ The genotype of an individual determines their phenotype, which is the observable trait.
• 👪 Children inherit one chromosome from each parent, which determines their genotype.

Questions & Answers

Q: How is color blindness represented in the pedigree chart?

In the pedigree chart, a colored-in square or circle indicates that the individual exhibits color blindness, while an empty square or circle represents non-color blindness.

Q: What are the genotypes of Tom and Barbara?

Tom is colorblind and has the genotype XcY, while Barbara is a carrier and has the genotype X+CXc.

Q: How many possible outcomes are there for Tom and Barbara's children?

There are four possible outcomes: colorblind female, carrier female, colorblind male, and non-colorblind male.

Q: What is the probability of their offspring being colorblind?

Out of the four possible outcomes, two of them result in colorblind offspring, making the probability 50%.

Summary & Key Takeaways

• The pedigree chart shows the inheritance of color blindness through three generations.

• Color blindness is an X-linked recessive trait.

• The probability of a child being colorblind can be determined by analyzing the genotypes of the parents.