Genetics problem please help the whole homework assignment is due tomorrow at 4:10 pm
Packrats exhibit many interesting behaviors. Let's say that the trait of bringing home fun shiny objects (controlled by the allele H) is dominant to the trait of bringing home dull boring objects (controlled by the allele h). The shiny object phenotype has a penetrance of 80%. Suppose two heterozygous individuals are crossed, and 30 offspring are produced.
(A) How many should like shiny objects?
(B) If there was a difference in expressivity, how would this affect the phenotype? Would it change your answer to (A)?
I am not familiar with the term penetrance. But to find part a, perform a cross between two Hh individuals and it should come out to like 75% like shiny objects.
To solve this problem, we need to understand the principles of dominance, penetrance, and expressivity in genetics.
Dominance: In this scenario, the allele for bringing home fun shiny objects (H) is said to be dominant over the allele for bringing home dull boring objects (h). This means that if an individual has at least one copy of the H allele, they will exhibit the shiny object phenotype.
Penetrance: Penetrance refers to the proportion of individuals with a particular genotype that actually show the associated phenotype. In this case, the shiny object phenotype has a penetrance of 80%. This means that out of all individuals with the H allele, 80% will exhibit the shiny object behavior.
Expressivity: Expressivity refers to the degree or extent to which a particular genotype is expressed as a phenotype. It describes the variation in phenotype among individuals with the same genotype. In the given problem, it is mentioned that there may be a difference in expressivity. This means that even among individuals with the H allele, the shiny object behavior may be expressed to varying degrees.
Now let's answer each part of the question:
(A) How many should like shiny objects?
To determine the number of offspring that will exhibit the shiny object phenotype, we need to consider the genotype of the parents. Each parent is heterozygous, which means they have one H allele (shiny object) and one h allele (dull object).
When two heterozygous individuals are crossed, the possible genotypes of the offspring can be represented as follows:
HH - 25% chance
Hh - 50% chance
hh - 25% chance
Since the allele for bringing home shiny objects (H) is dominant, both the HH and Hh genotypes will result in the shiny object phenotype. Therefore, the number of offspring that should like shiny objects is the sum of the frequencies of HH and Hh genotypes. In this case, it is 25% + 50% = 75%.
Out of the 30 offspring, 75% of them should like shiny objects. Therefore, 0.75 * 30 = 22.5 offspring (or approximately 23 offspring) should like shiny objects.
(B) If there was a difference in expressivity, how would this affect the phenotype? Would it change your answer to (A)?
If there is a difference in expressivity, it means that even individuals with the same genotype (HH or Hh) may show different levels of the shiny object behavior. In this case, expressivity affects the degree to which the phenotype is expressed.
However, the difference in expressivity does not affect our answer to part (A) because we were asked about the number of offspring that would exhibit the shiny object phenotype, regardless of the degree of expressivity. So, regardless of the variation in expressivity, the answer to part (A) remains the same, which is approximately 23 offspring.