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Flashcards in Quantitative Genetics Deck (36)
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1
Q

Measurable in numeric terms.

-Polygenic and multifactorial

A

Quantitative traits

2
Q
  • Have quantitative traits
  • Phenotypes of Q.T. are distributed along a continuum; series of intermediate phenotypes that fall between 2 extremes
    ex. Human height, IQ, dispostion, life-span, metabolism
A

Continuous variation

3
Q

No degrees of severity

A

Most traits studied so far that have very distinct phenotypes

4
Q

Clearly defined by one or a few genes

-In nature, the majority of traits do not follow this mode of expression

A

Discrete phenotypes

5
Q
  • Controlled by multiple genes and environmental factors
  • Each gene is inherited using Mendelian principles
  • Modifier genes, differential gene expression, etc. blend together discrete traits
A

Quantitative Traits

6
Q

Mode of study that shows inheritance of quantitative traits.

A

Quantitative Genetics

7
Q

Number of copies of these alleles influence the degree of severity of a trait

A

Contributing alleles (a.k.a. additive alleles)

8
Q

Color of Wheat Kernels Example

A
  • Vary in color from white to dark red

- Alleles A (red) and B (crimson) result in red pigment, while a and b alleles do not produce pigment

9
Q

One gene variation

A

F2: 1:2:1 incomplete dominance

increasing Left to right Red and and contributing alleles

10
Q

Two gene variation

A

F2: 1:4:6:4:1
aabb: 2Aabb and 2aaBb: AABB
Increasing red and contributing alleles

11
Q

Three gene variation

A

F2: 1:6:15:20:15:6:1

increasing red and contributing alleles

12
Q

More gene pairs result in_______.

A

“Bell shaped curve”

-Environment “blurs” phenotypic classes.

13
Q

Samples and Populations

A
  • Too difficult to collect data from every individual for a large population
  • Sample a random subset of the population
  • Population: entire group of individuals
  • Sample: a representative subset
  • Sample should be randomly selected and large enough
  • Unbiased sample: define the rules before experiment
14
Q

Summary of continuous phenotype variance for a group or a population
ex. Human birth weight

A

Distribution

15
Q

Number to individuals in a sample are plotted (according to phenotype) as a histogram.

A

Distribution for a quantitative trait

16
Q

Curve of distribution

A

Lots of phenotypic variance makes a broader curve

17
Q

Nature is not:

A

In opposition to nurture

18
Q

Nature is:

A

In correspondence with nurture, influencing one another.

19
Q

How much variation in a phenotype is due to genetic variation versus environmental variation?

A

Ex: Superior strains of wheat in a field.
Strains=genetics
Field=environment
In humans, environment influences genetics and subtle choices which influence phenotype.

20
Q
  • Causes variation within each genotypic class
  • Causes “blurring” btwn. phenotypic classes in a continuous distribution
  • Studied with modern genotyping methods (PCR, etc)
A

Enviornment affects/quantitative traits

21
Q

Vp=Vg+Ve+Vg*e

A

Phenotypic Variance for a trait

22
Q

genotypic variance contribution of allelic differences at multiple genes
ex. genetic trends in height

A

Vg

23
Q

environmental variance contribution from non-genetic sources

ex. impact of nutrition on human height

A

Ve

24
Q

genotype-by-enviornment variance

A

Vg*e

25
Q

Example: Milk production in dairy cows

A
  • environmental and genetic influences
  • How much variation is genetic?
    • use this info to see if we should selectively breed the cattle
  • We have 4 breeds(<—genotype) of cows
  • Collect mild production data from sample of each breed
  • Do statistical analysis to determine if any difference is significant.
26
Q

How much of the phenotypic differences are due to genetic factors.

A

Heritability

27
Q

None of the variation in phenotype between individuals results from genetic differences (all environmental)

A

0 heritability factor

28
Q

Half of the phenotypic variation is due to genetic differences between individuals and half is due to the environment

A

0.5 heritability factor

29
Q

All variation is genetically based

A

1 heritability factor

30
Q

Example: Fruit Fly egg size in relation to temp

A

Observation: over many generations, fruit fly egg size increases in cold temps
Question: How much of the size difference is due to the environment versus genetic differences (evolution)?

31
Q

Example: Fruit Fly egg size cont…

A

Vp=Vg+Ve

  • Transfer the cold fruit flies to warm (control) temps and mate
  • Transfer the control flies to the cold and mate
  • Measure egg size of F2 generation (b/c of maternal effect)
  • Using stats of egg size measurement, see if there is a difference in the mean egg size of progeny
  • The difference between the two is Vg.
32
Q

What about humans?

A

Monozygotic twins: phenotypic variance due to Ve

33
Q

True or False? Traits shared by members of the same family do not necessarily have high heritability.

A

True.

-They have similar environments.

34
Q

Individual loci that play a role in quantitative traits.

A

Quantitative trait loci (QTL)

35
Q

All QTL and how they interact.

A

Genetic architecture of a trait.

36
Q

Study of QTL

A

Use molecular tools and statistics to link quantitative phenotypes and QTLs.