Quantitative genetics Flashcards

1
Q

Types of variation – discrete

A

AKA - discontinuous, categorical, mendelian

Discrete classes of phenotype

No intermediates

Follows mendelian ratios

Simple genetic basis, limited effect of the environment

E.g. blood groups, red/white pea flowers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Types of variation – continuous

A

AKA - quantitative, complex, multifactorial

Phenotypes do not fall into classes

Offspring of intermediate phenotype

Cannot observe mendelian ratios

Complex genetic basis plus effect of the environment

E.g. height, beak size

The combined effects of several polymorphic loci result in a nearly continuous distribution

Quantitative traits are heritable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Types of variation – threshold

A

Appears discontinuous but caused by continuous distribution

Distribution is called liability

Phenotype depends on critical threshold

No simple segregation in families

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How can genes cause continuous variation?

A

Polygenic traits, such as height or weight, are determined by the combined effects of many genes that contribute to the trait

Each of these genes may have a small effect on the trait, but together they can add up to produce a wide range of phenotypic variation

In addition, environmental factors, such as nutrition, exercise, and exposure to toxins, can also affect the expression of these genes and contribute to the overall phenotype.

Continuous variation can also arise through interactions between genes and the environment.

E.g. some genes may only be expressed in response to specific environmental cues or conditions, leading to different phenotypes under different environmental conditions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Continuous traits heritable?

A

Looking at twin studies
-If trait similarity is due to genes, not environment, correlation should be stronger in monozygotic twins rather that dizygotic twins
-Should still be present even if twins reared apart

Continuous traits influenced by genetics and environment

Environmental variance complicates the inference of the effects of genotypes at individual loci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly