The tortoiseshell cat has a combination of black and orange fur. The gene for black fur is represented by $X^b$ and the gene for orange fur is represented by $X^o$. A tortoiseshell female cat ($X^b X^o$) mates with an orange male cat ($X^o Y$). Which alternative shows the probable percentages of coat colours in the litter of kittens?

SSCE HSC Biology Adaptations and survival: The tortoiseshell cat has a comb

The tortoiseshell cat has a combination of black and orange fur - HSC - SSCE Biology - Question 15 - 2003 - Paper 1

Question 15

The tortoiseshell cat has a combination of black and orange fur. The gene for black fur is represented by $X^b$ and the gene for orange fur is represented by $X^o$. ... show full transcript

Worked Solution & Example Answer:The tortoiseshell cat has a combination of black and orange fur - HSC - SSCE Biology - Question 15 - 2003 - Paper 1

Step 1

Determine Parental Genes

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Answer

The tortoiseshell female cat has genotype $X^b X^o$ and the orange male cat has genotype $X^o Y$ .

Step 2

Set Up Punnett Square

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Answer

To find the potential genotypes of the offspring, we create a Punnett square with the female and male genotypes:

          X^o      Y
        ----------------
     X^b | X^b X^o | X^b Y  
     X^o | X^o X^o  | X^o Y

This square shows the possible combinations of the two parents' alleles.

Step 3

Analyze Offspring Genotypes

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Answer

The potential offspring genotypes are:

$X^b X^o$ (tortoiseshell female)
$X^o X^o$ (orange female)
$X^b Y$ (black male)
$X^o Y$ (orange male)

Step 4

Calculate Percentages

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Answer

From the genotypes, we can derive the following percentages:

25% tortoiseshell females ( $X^b X^o$ )
25% orange females ( $X^o X^o$ )
25% black males ( $X^b Y$ )
25% orange males ( $X^o Y$ )

Step 5

Select Correct Alternative

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Answer

The final answer shows that each coat color is represented equally among the offspring. Therefore, the correct alternative is:

(D) 25% tortoiseshell females, 25% orange females, 25% black males, 25% orange males.

The tortoiseshell cat has a combination of black and orange fur - HSC - SSCE Biology - Question 15 - 2003 - Paper 1

Worked Solution & Example Answer:The tortoiseshell cat has a combination of black and orange fur - HSC - SSCE Biology - Question 15 - 2003 - Paper 1

Determine Parental Genes

Set Up Punnett Square

Analyze Offspring Genotypes

Calculate Percentages

Select Correct Alternative

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