Quantitative Genetics

Question 1

What are most genetic traits (discontinuous or continuous variation) that have been studied?

Answer 1

Discontinuous variation

Question 2

What are discontinuous variation?

Answer 2

• Distinct categories
• Tend to be qualitative
• Controlled by a few genes
• Unaffected by the environment

Question 3

What are continuous variations?

Answer 3

• No distinct categories
• Tends to be quantitive
• Controlled by a lot of genes
• Strongly influenced by the enviroment

Question 4

What is quantitative genetics?

Answer 4

The study of continuously measured traits (such as height or weight) and their mechanisms.

Question 5

What are three types of polygenic traits?

Answer 5

• Metric
• Meristic
• Threshold

Question 6

What are the types of polygenic traits based on?

Answer 6

Theoretical assumption of an underlying normal distribution

Question 7

What is metic?

Answer 7

Continuous scale

Question 8

What is meristic?

Answer 8

Discrete scale

Question 9

What is threshold?

Answer 9

Present or absent

Question 10

What are different types of metric traits?

Answer 10

• Mean

- Popluation variance

Question 11

What is mean?

Answer 11

The central of phenotypic distribution

Question 12

What is population variance?

Answer 12

The average squared deviation from the mean is called the variance

Question 13

Why is quantitative genetics important?

Answer 13

• Medicine
• Agriculture
• Conservation

Question 14

How is quantitative genetics important for medicine?

Answer 14

• Susceptibility to disease
• Complex disorders caused by multiple genetic and environmental factors
• Understanding genetic vs environmental causes
• Prevention
• Genetic counselling
• Genetically-tailored treatments

Question 15

How is quantitative genetics important for agriculture?

Answer 15

• Economically important traits = quantitative traits.
• Quantitative genetics theory and the basis for selective breeding
• Environmental variation reduces efficiency of selection

Question 16

How is quantitative genetics important for conservation?

Answer 16

Conservation of:

• endangered species
• captive breeding programmes

Consequences of inbreeding and outcrossing.

Question 17

Are quantitative genetics fundamentally different from the Mendelian patterns of inheritance that you have been studying previously?

Answer 17

NO …traits are still determined by alleles of genes that are inherited following the laws of segregation and independent assortment

BUT …now we must consider traits that are influenced by many genes and are also influenced by the environment

Question 18

Finish:

Phenotype =…

Answer 18

genotype + environment

Question 19

What is the variation in population related to?

Answer 19

Vp = VG + VE + VGE

Question 20

What does VP stand for?

Answer 20

Phenotypic Variation

Question 21

What does VG stand for?

Answer 21

Genetic variance

Question 22

What does VE stand for?

Answer 22

Environmental variance

Question 23

What does VGE stand for?

Answer 23

Genetic x environmental interaction variance

Question 24

What can phenotypic variation in a trait be?

Answer 24

Partitioned

Question 25

How can VG be partitioned into variation?

Answer 25

- Alleles present or additive effects (VA) - Dominance interaction (VD) - Epistatic interactions (VI)

Question 26

What is the VG equation?

Answer 26

VG = VA + VD + VI

Question 27

What is additive effect?

Answer 27

Effect of adding alleles

Question 28

What is dominance interaction?

Answer 28

Two alleles at the same locus

Question 29

What is epistatic interaction?

Answer 29

Alleles at different locus

Question 30

What is Genetic variance [VG]?

Answer 30

Contribution to phenotypic variation due to set of alleles present in a population and their interactions

Question 31

What is Environmental variance [VE]?

Answer 31

Contribution to phenotypic variation caused by differences in environmental conditions (E for environment)

Question 32

What is broad sense heritability?

Answer 32

Measures the importance of genetic variation (VG) relative to total variation (VP) in the phenotype

Question 33

What is the equation for broad sense heritability?

Answer 33

H^2 = VG/VP

Question 34

What is heritability of trait?

Answer 34

Describes how much variation is genetic

Question 35

What is narrow sense heritability?

Answer 35

Measures the importance of additive genetic variation (VA) or variation due to the alleles present in the population, relative to total variation (VP) in causing variation in the phenotype.

Question 36

What is the equation for narrow sense heritability?

Answer 36

H^2 = VA/VP

Question 37

What should the theoretical H^2 vary between?

Answer 37

0 and 1

Question 38

What does H^2 estimate?

Answer 38

Predict change in the population mean under selection

Question 39

Finish the sentence: | When H^2 increases, the response to...

Answer 39

selection increases

Question 40

Relating to y = mx + c what is h^2 equal to?

Answer 40

M

Question 41

What is the infinitesimal model?

Answer 41

A simple model of the inheritance of quantitative traits, which assumes an infinite number of unlinked loci, each with an infinitesimal effect

Question 42

Finish the sentence: | Infinite number of genes controlling a .....

Answer 42

phenotypic trait each with a very small effect