Two homozygous strains of corn are hybridized. They are distinguished by six dif

Question

Two homozygous strains of corn are hybridized. They are distinguished by six different pairs of genes, all of which assort independently and produce an independent phenotypic effect. The F1 hybrid is selfed to give an F2 generation.

a) What is the number of possible genotypes in the F2 plants?
b) How many of these genotypes will be homozygous at all six gene loci?
c) If all gene pairs act in a dominant recessive fashion, what proportion of the F2 plants will be homozygous for all dominants?
d) What proportion of the F2 will show all dominant phenotypes?

Explanation / Answer

What is the number of possible genotypes in the F2 plants?
3^n = 3^6 = 729
1. AABBCCDDEE
2. AABBCCDDEe
3. AABBCCDDee
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?? AaBBCCDDEE
?? AaBBCCDDEe
...
...
728. aabbccddEe
729. aabbccddee


How many of these genotypes will be homozygous at all six gene loci?
2^n = 2^6 = 64
1. AABBCCDDEE
2. AABBCCDDee
...
...
63. aabbccddEE
64. aabbccddee


If all gene pairs act in a dominant-recessive fashion, what proportion of the F2 plants will be homozygous for all dominants?
1/4096
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What proportion of the F2 will show all dominant phenotypes?
3/4 x 3/4 x 3/4 x 3/4 x 3/4 x 3/4 = 729/4096
A-B-C-D-E-

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