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Home Q & A Board Biology-Related Homework Help Cell Biology
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oldcollegelady oldcollegelady
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13 years ago
A dihybrid cross between and plant with long smooth leaves and a plant with short hairy leaves produces a F2 plant with long smooth leaves.
The question is: Consider a long smooth F2 plant. This plants genotype:
a. must be homozygous for both long alleles and smooth alleles
b. must be heterozygous at both the leaf length gene, and the leaf hair gene.
c. can only be inferred by another cross
d. cannot be determined by any means

my answer was b, but the book's anwer was c. Can you explain why it is c?

thanks Wink Face
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#1
Staff Member
13 years ago
Absolutely - you have to do a back-cross in order to make sure what the original parents were. If both parents were say, heterozygous for both genes, then there would be a 9:3:3:1 phenotype. Four different phenotypes, three of which show similar traits. In other words, if the offspring was homozygous recessive, so a 1 and 16 chance, it wouldn't be a good idea to assume that the parents are also homozygous recessive because they may have a heterozygous genotype (i.e. TtGg) and still produce a homozygous recessive.
- Master of Science in Biology
- Bachelor of Science
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#2
13 years ago
 Kissing Face with Closed Eyes
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#3
Staff Member
13 years ago
Face with Stuck-out Tongue
- Master of Science in Biology
- Bachelor of Science
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