If lethal alleles (alleles that kill) are homozygous and black hair is
dominant over blonde hair, cross a black haired normal person
heterozygous for both traits with a blonde person who is heterozygous
for the normal trait. How many blone offspring will live?

Hi Jennifer,

Our lethal allele is L (dominant - harmless) and l (recessive - lethal).
Our hair color allele is B (dominant - black) and b (recessive - blonde).

You have one LlBb person and one Llbb person.

This means that you've got the following possible crosses (with ratios
out of eight possibles):

LLBb (living, black hair) : 1
LLbb (living, blonde) : 1
LlBb (living, black hair) : 2
Llbb (living, blonde) : 2
llBb (dead, black hair) : 1
llbb (dead, blonde): 1

So, three of the blonde offspring will live, for each eight offspring
created.  In this case, since the blonde parent can only contribute a
recessive b allele, you know that all of the offspring will at least
be heterozygous for hair color.  That makes this question trickier
than it could have been.

Librariankt

The ratio is 3:1
thats 3 with black hair and 1 with blonde.