Question 1 of 10 2 Points
Earlobes can be either attached or detached. The allele for attached earlobes
is recessive (e), and the allele for detached earlobes is dominant (E). What
must be true if a boy is born with attached earlobes?
A. He has a heterozygous genotype.
O B. He has no E alleles.
C. He has no recessive alleles.
O D. He has one of each allele,
SUBMIT

B. He has no E alleles.

Explanation:

In order for the boy to have an attached earlobes phenotype, he must have no E alleles, because the E is dominant. So his genotype must be ee. If he has even just a single E allele (like Ee) he will have detached earlobes, because the dominant trait will mask the expression of the recessive trait.

Why not A or D: Heterozygous Ee (one of each allele) would result in detached earlobes.

Why not C: If he has no recessive alleles, EE, he would have detached earlobes.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)