Respuesta :
Answer:
First thing you need to do is get the alleles of the mother and father. They are heterozygous dominant for freckles, their genotypes are Ff. Your Punnett would look like this:
P generation cross: Ff x Ff
F f
F FF Ff
f Ff ff
Looking at the Punnett, just list all the possible genotype combinations, then count how many you see in the Punnett. But when you tlak about phenotype, you will be looking at what was expressed. Since Freckles are dominant, when there is at least 1 dominant allele in the combination, the dominant trait will be expressed.
Genotype Number Phenotype
FF 1 Freckles
Ff 2 Freckles
ff 1 No Freckles
You can see that FF and Ff will both express freckles, so you add up their ratio.
Based on this:
genotype ratio would be 1 FF: 2 Ff: 1 ff or 1:2:1
phenotype ration would be: 3 Freckles: 1 No freckles or 3:1
Question no 1:
As mentioned in the question that parents are heterozygous for freckles (Ff).
Please see the punnet square in attached picture.
Question no 2:
As we can see in figure offspring will be as:
P1: Ff X Ff
F1: FF: Ff : Ff : ff
Phenotypic ratio: 3: 1
Genotypic ratio: 1: 2: 1
This is because freckles is a dominant trait and even one allele of dominant treat is enough to cause freckles to the offspring. However genotypically there is a difference between FF and Ff because the Ff will have lower chances to inherit the trait to offspring and FF will have more chances to transfer the trait to next offspring.
Hope it helps!