Penetrance and Expressivity quiz #1 Flashcards
Penetrance and Expressivity quiz #1
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Which of the following statements is true regarding incomplete penetrance?
Incomplete penetrance occurs when not all individuals with a specific genotype display the associated phenotype; only a certain percentage of individuals with the allele actually express the trait. If a geneticist describes a trait as being 70% penetrant, what does this mean?
It means that 70% of individuals with the genotype for the trait actually show the phenotype, while 30% do not express the trait despite having the genotype. What is one reason why an organism's genotype might not match its expected phenotype?
Environmental factors can mask the phenotype, preventing the expected trait from being expressed. How can gene interactions affect phenotype expression?
Gene interactions such as epistasis, modifiers, or suppressors can alter or prevent the expression of a phenotype associated with a specific genotype. What does expressivity measure in genetics?
Expressivity measures the degree or intensity to which a given allele is expressed in the phenotype, which can vary among individuals. Give an example of variable expressivity in a trait.
Brown fur color can show variable expressivity, ranging from dark brown to light brown and all shades in between. How does penetrance differ from expressivity?
Penetrance refers to the percentage of individuals with a genotype who show the phenotype, while expressivity describes the range or intensity of the phenotype among those who express it. What might make a phenotype difficult to observe even if the genotype is present?
A phenotype may be subtle or have a mild expression, making it hard to detect even when the genotype is present. In a group of five organisms with the same genotype, only three show the expected phenotype; what concept does this illustrate?
This illustrates incomplete penetrance, where not all individuals with the genotype express the phenotype. What role do suppressor genes play in phenotype expression?
Suppressor genes can inhibit the expression of a phenotype, causing the expected trait to not appear even if the genotype is present.