Chapter 11 Exam 3

Question 1

What are polygenic traits?

Answer 1

Polygenic traits are those controlled by two or more genes

-examples: skin color, hair color, eye color, immune system function, and the oxygen carrying capacity of blood

Question 2

What are multifactoral traits?

Answer 2

polygenic traits that also are affected by environmental factors. examples: height and weight

Question 3

What are continuous traits?

Answer 3

those which have a range of ‘phenotypic values’ that don’t fall into specific precise groups, height and weight are good examples, they have a broad distribution of values with many intermediate values being possible that can be always measured more and more finely

Question 4

What are threshold traits?

Answer 4

Threshold traits typically have two alternative phenotypes, unaffected or affected. Individuals display the trait if they cross a ‘threshold’. Multiple genes and environmental factors still contribute to the phenotypes. Many disease traits like diabetes or heart disease are threshold traits

Question 5

What is heritability?

Answer 5

Heritability is the ratio of the contribution of genetics to a trait’s phenotype divided by the total conribution of the environment and genetics.

• it varies from 0 to 1
• if there is a high genetic component, then the heritability of the trait is nearly 1
• if there is a low genetic component, or a high environmental component, then the heritability of the trait is close to 0