a common recessive trait in dogs is deafness. homozygous line of normal-hearing dogs was crossed with a homozygous line of deaf dogs. F1 and F2 generations were produced. What % of F1 generation is expected to have normal hearing? What is a phenoeyeic ratio of the F2 generation?
You’re answer is wrong because if they’re both homozygous parents, one dominant and one recessive, their genotypes would be DD x dd
What is the answer
Let:
D=normal
and
d=recessive
P1:
DD x Dd
F1:
1DD : 2Dd : 1dd
66% should have normal hearing.
The second question is incomplete.
I should have said 75%, but the second question still can not be answered.
For his 2nd Experiment, Gregor Mendel self-fertilized plants from the First generation to produce the second generation. However, dogs can’t self-fertilize. So you should use two offspring from the first generation to produce the second generation.
Well, it seems we have some doggy genetics going on here. Let me calculate this for you, but first, let me put on my "paws" and see what we can find.
If we have a homozygous line of normal-hearing dogs crossed with a homozygous line of deaf dogs, we can determine the expected percentage of normal hearing in the F1 generation.
Since deafness is a recessive trait, we can represent normal hearing as the dominant trait (let's call it "N") and deafness as the recessive trait (let's call it "d").
In this case, the homozygous line of normal-hearing dogs would be NN, and the homozygous line of deaf dogs would be dd.
When we cross these two, all the offspring in the F1 generation will have one copy of each gene, resulting in the genotype Nd.
To find the percentage of F1 dogs with normal hearing, we need to determine how many of these have one copy of the normal hearing gene (N). Since there are two possible outcomes (Nd and Nd), 50% of the F1 generation would have normal hearing.
Now, let's move on to the F2 generation's phenotypic ratio.
In the F1 generation, as we mentioned earlier, all the dogs have the genotype Nd. When we cross these dogs with each other, we can expect various combinations of genotypes and phenotypes.
The possible genotypes in the F2 generation are NN, Nd, and dd. And based on our knowledge of classical genetics, we can determine the expected ratio of these phenotypes.
Using a Punnett Square, we find that the phenotypic ratio of the F2 generation would be:
- 25% normal hearing (NN)
- 50% carrying the deafness trait (Nd)
- 25% deaf (dd)
So, in the F2 generation, we have a phenotypic ratio of 1:2:1 for normal hearing:carriers:deafness, or if you prefer, a "Canine Sonata" of 1 normal hearing dog, 2 carrier dogs, and 1 deaf dog.
I hope that answers your question and brings a smile to your face!
To determine the expected percentage of normal-hearing dogs in the F1 generation, we need to understand the inheritance pattern of deafness in dogs.
Deafness in dogs is often caused by a recessive gene. This means that for a dog to be deaf, it must inherit two copies of the deafness-causing allele, one from each parent. Let's designate the dominant allele for normal hearing as "N" and the recessive allele for deafness as "n."
When a homozygous line of normal-hearing dogs (NN) is crossed with a homozygous line of deaf dogs (nn), all the F1 generation offspring (Nn) will inherit one copy of the normal allele and one copy of the deafness-causing allele.
Now let's calculate the percentage of F1 generation expected to have normal hearing:
Since the normal allele (N) is dominant, any dog with at least one copy of this allele will have normal hearing. Therefore, the F1 generation will have a 100% chance of having normal hearing.
So, 100% of the F1 generation is expected to have normal hearing.
Moving on to the phenotypic ratio of the F2 generation, we need to consider the possible genotypes that can be produced from crossing the F1 generation dogs (Nn x Nn). The Punnett square is a useful tool to determine the possible combinations:
N N
------------
N | NN | NN |
------------
n | Nn | nn |
------------
As we can see from the Punnett square, there are three possible genotypes: NN, Nn, and nn. Among these genotypes, NN and Nn represent dogs with normal hearing, while nn represents dogs that are deaf.
The phenotypic ratio is the ratio of observed physical traits. In this case, there are three possible phenotypes: normal hearing (NN and Nn) and deaf (nn). Therefore, the phenotypic ratio of the F2 generation would be 3:1, indicating that for every three dogs with normal hearing, there would be one deaf dog.
So, the pheno