Question

question 8 (1 point)
the pedigree below tracks the presence of attached earlobes through a familys generation. having attached earlobes is an autosomal recessive trait.
what is the genotype of individual i-1?

a x^a y
b fe
c ee
d x^a y
e ee

Explanation:

1. First, recall that attached earlobes is an autosomal recessive trait. So, individuals with attached earlobes (filled in the pedigree) have the genotype \( ee \), and those with free earlobes (unfilled) can be \( EE \) or \( Ee \).
2. Individual I - 1 is a male with free earlobes (unfilled square). Since his partner (I - 2) has attached earlobes (\( ee \)) and they have offspring (II - 2 and II - 3). Let's analyze the cross: If I - 1 were \( EE \), all offspring would get a dominant allele from him and a recessive allele (\( e \)) from I - 2, so all offspring would be \( Ee \) (free earlobes). But II - 2 has attached earlobes (\( ee \)), which means I - 1 must have passed on a recessive allele (\( e \)). So I - 1's genotype must be \( Ee \) (because he has free earlobes, so he has at least one \( E \), and he must have an \( e \) to pass on to the offspring with attached earlobes). Wait, but wait, the options: Wait, the options are a. \( X^E Y \) (X - linked dominant? No, the trait is autosomal recessive as per the problem statement: "autosomal recessive trait". Wait, maybe I misread. Wait, the problem says "autosomal recessive trait", so it's not X - linked. Wait, the options include \( Ee \) (option b), \( EE \) (option c), \( X^e Y \) (option d), \( X^E Y \) (option a), and \( ee \) (option e). Since it's autosomal recessive, the genotype should be in terms of \( E \) and \( e \), not X - linked. Individual I - 1 is a male with free earlobes (dominant phenotype). His wife (I - 2) has attached earlobes (\( ee \)). Their daughter (II - 2) has attached earlobes (\( ee \)), so she must have received one \( e \) from each parent. Therefore, I - 1 must have an \( e \) allele to pass on, and since he has free earlobes (dominant), his genotype is \( Ee \). Wait, but the options: Let's check the options again. Option b is \( Ee \), option c is \( EE \), option e is \( ee \) (but he has free earlobes, so not \( ee \)). Since it's autosomal, X - linked options (a, d) are incorrect. So the correct genotype for I - 1 (male, free earlobes, father of a child with attached earlobes) is \( Ee \).

Answer:

b. \( Ee \)