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In mice, two genes and their alleles are Gene for hair colour B black Gene for hair length L short l long These genes assort independently - VCE - SSCE Biology - Question 4 - 2005 - Paper 1
Question 4
In mice, two genes and their alleles are Gene for hair colour B black Gene for hair length L short l long These genes assort independently. A mouse with shor... show full transcript
Worked Solution & Example Answer:In mice, two genes and their alleles are Gene for hair colour B black Gene for hair length L short l long These genes assort independently - VCE - SSCE Biology - Question 4 - 2005 - Paper 1
Step 1
A mouse with short, black hair was crossed with a mouse with long, brown hair.
Answer
To determine the genotype of the parent mouse with short, black hair, we need to analyze the genetic traits being inherited. The short hair is represented by the dominant allele (L), and the black hair is also represented by the dominant allele (B). Since both traits are dominant, the genotype of the short, black-haired mouse must include at least one dominant allele for each trait.
Step 2
Half of the resulting offspring had short hair.
Answer
If half of the offspring from this cross exhibited short hair, we know that at least one parent contributed a dominant L allele. Therefore, the genotype of the black-haired parent is potentially LL or Ll, since if it had both recessive alleles (ll), none of the offspring would have short hair.
Step 3
Half of the offspring had black hair.
Answer
The fact that half of the offspring had black hair indicates that the black-haired mouse must be heterozygous for the hair color trait. Therefore, the genotype must be Bb. Hence, if we combine these conclusions, the genotype of the short, black-haired mouse must be LLBb, as it provides both a dominant allele for short hair and a mix for hair color.
Step 4