can't find answer to biology ?

[FredBurroughs]

if someone could answer this for me, i'd be grateful. i've spent the last 2 nights trying to figure it out....

Attached earlobes are recessive to free earlobes. What genotypic ratio is expected when an individual with attached earlobes mates with an individual heterozygous for free earlobes?

a. 2:1
b. 9:3:3:1
c. 1:1
d. 1:2:1
e. 3:1

I have a really unhelpful Biology book, so if someone could explain the answer, that would be great!

[mith]

http://biology-online.org/biology-forum ... are#p96192

[Cat]

Attached earlobes (a) are recessive to free earlobes (A).
What genotypic ratio is expected when an individual with attached earlobes (aa) mates with an individual heterozygous for free earlobes (Aa)?

Aa x aa => 50% Aa + 50% aa => 1:1