An organism has three independently assorting traits AaBbCc. What fraction of its gametes will contain the recessive gene abc?
To determine the fraction of gametes that will contain the recessive gene abc, we need to assess the segregation of the traits. In this case, we have three independently assorting traits: A, B, and C. This means that the inheritance of one trait does not affect the inheritance of the others.
Each of the traits has two alleles, with uppercase representing dominant alleles and lowercase representing recessive alleles. So, for trait A, we have A (dominant) and a (recessive), for trait B, we have B (dominant) and b (recessive), and for trait C, we have C (dominant) and c (recessive).
Since the traits assort independently, we can determine the possible combinations of alleles for each trait by multiplying the number of possibilities for each trait. In this case, there are 2 possibilities for each trait (1 dominant and 1 recessive).
So, for the AaBbCc organism, the possible combinations of alleles are:
AA BB CC
AA BB Cc
AA Bb CC
AA Bb Cc
Aa BB CC
Aa BB Cc
Aa Bb CC
Aa Bb Cc
Out of the eight possible combinations, only one contains the recessive alleles for all three traits: AaBbCc. Therefore, 1 out of 8 gametes will contain the recessive gene abc.
Therefore, the fraction of gametes that will contain the recessive gene abc is 1/8 or 0.125.