Question

a male beetle has the genotype ttbb. if this beetle mates with a female with genotype ttbb, what is the chance their offspring will have the genotype ttbb? 12/16 4/16 3/16 8/16

Explanation:

Step1: Split into single-gene crosses

First, analyze the T/t gene cross: Male (Tt) × Female (TT).
Possible offspring genotypes for T/t: TT (50%), Tt (50%), so probability of Tt is $\frac{1}{2}$.

Next, analyze the B/b gene cross: Male (bb) × Female (Bb).
Possible offspring genotypes for B/b: Bb (50%), bb (50%), so probability of Bb is $\frac{1}{2}$.

Step2: Multiply independent probabilities

Use the product rule for independent traits:
$\text{Probability of TtBb} = P(\text{Tt}) \times P(\text{Bb})$
$\text{Probability of TtBb} = \frac{1}{2} \times \frac{1}{2} = \frac{1}{4} = \frac{4}{16}$

Answer:

$\frac{4}{16}$