Question
A cat breeder is trying to breed long-haired cats. The short-haired (N) allele is dominant. This particular breed of cat has one gene for long hair (n) that is recessive. The cat breeder crosses a homozygous dominant cat with a heterozygous cat.
How likely are they to get long-haired cats? Why?
A.
0%, the homozygous dominant cat will only pass on the gene for short hair and so the phenotype will be short hair for all of the offspring.
B.
25%, the offspring will inherit a long-haired allele from each parent and, therefore, one of four of the offspring will be long-haired.
C.
50%, the heterozygous cat will pass on the gene for long hair and so the phenotype will be long hair for half of the offspring.
D.
75%, three out four of the offpsring will inherit the dominant allele (N) from each parent and, therefore, one of four of the offspring will be long-haired.
How likely are they to get long-haired cats? Why?
A.
0%, the homozygous dominant cat will only pass on the gene for short hair and so the phenotype will be short hair for all of the offspring.
B.
25%, the offspring will inherit a long-haired allele from each parent and, therefore, one of four of the offspring will be long-haired.
C.
50%, the heterozygous cat will pass on the gene for long hair and so the phenotype will be long hair for half of the offspring.
D.
75%, three out four of the offpsring will inherit the dominant allele (N) from each parent and, therefore, one of four of the offspring will be long-haired.
Answers
GPT-4o mini
To determine the likelihood of getting long-haired cats from the cross between a homozygous dominant cat (NN) and a heterozygous cat (Nn), we can set up a simple Punnett square.
1. The homozygous dominant cat (NN) can only contribute the dominant allele (N).
2. The heterozygous cat (Nn) can contribute either the dominant allele (N) or the recessive allele (n).
Here's how the Punnett square would look:
```
N N
-----------------
N | NN NN |
-----------------
n | Nn Nn |
-----------------
```
From the Punnett square, we can see the possible genotypes of the offspring:
- 2 NN (homozygous dominant)
- 2 Nn (heterozygous)
This means that all offspring will have at least one dominant allele (N) and therefore will all exhibit the short-haired phenotype (since short hair is dominant).
Thus, there is a **0% chance** of getting long-haired cats, as long-haired (n) is recessive and can only be expressed if two recessive alleles (nn) are present.
Therefore, the correct answer is:
**A. 0%, the homozygous dominant cat will only pass on the gene for short hair and so the phenotype will be short hair for all of the offspring.**
1. The homozygous dominant cat (NN) can only contribute the dominant allele (N).
2. The heterozygous cat (Nn) can contribute either the dominant allele (N) or the recessive allele (n).
Here's how the Punnett square would look:
```
N N
-----------------
N | NN NN |
-----------------
n | Nn Nn |
-----------------
```
From the Punnett square, we can see the possible genotypes of the offspring:
- 2 NN (homozygous dominant)
- 2 Nn (heterozygous)
This means that all offspring will have at least one dominant allele (N) and therefore will all exhibit the short-haired phenotype (since short hair is dominant).
Thus, there is a **0% chance** of getting long-haired cats, as long-haired (n) is recessive and can only be expressed if two recessive alleles (nn) are present.
Therefore, the correct answer is:
**A. 0%, the homozygous dominant cat will only pass on the gene for short hair and so the phenotype will be short hair for all of the offspring.**