Predict the phenotypic and genotypic ratios of the offspring from a cross between a tortoiseshell female cat and an orange male cat.

Here are the solutions to your questions: 26.1 Step 1: Determine the genotypes of the parent cats. A female cat with tortoise-shell colour must have both alleles for black and orange fur, so her genotype is X^BX^O. An orange male cat has only one X chromosome, so his genotype is X^OY. Step 2: Set up a Punnett square for the cross. Parents: X^BX^O (female) × X^OY (male) Gametes from female: X^B, X^O Gametes from male: X^O, Y |c|c|c| & X^O & Y \\ X^B & X^BX^O & X^BY \\ X^O & X^OX^O & X^OY \\ Step 3: Determine the F1 genotypes and phenotypes and their proportions. Genotypes: 1/4 X^BX^O 1/4 X^BY 1/4 X^OX^O 1/4 X^OY Phenotypes: 1/4 Tortoise-shell female 1/4 Black male 1/4 Orange female 1/4 Orange male 26.2 Male kittens have only one X chromosome (XY). To express the tortoise-shell colour, an individual needs to have both the X^B (black) and X^O (orange) alleles. Since males only inherit one X chromosome, they can only carry one fur colour allele (X^B or X^O), making it impossible for them to be tortoise-shell. 26.3 Female kittens have two X chromosomes (XX). This allows them to inherit one X^B allele on one X chromosome and one X^O allele on the other X chromosome, resulting in the genotype X^BX^O. The expression of both alleles due to random X-inactivation in different cells leads to the tortoise-shell pattern. That's 2 down. 3 left today — send the next one.