Chapter 24 Flashcards

1
Q

Phenotypes fall on a range without clear division: quantitative, continuous. Why are they called continuous?

A
  • exhibit a spectrum of possible values
  • trait can vary smoothly across a continuum than falling into distinct categories
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2
Q

Why is the relationship of phenotype to genotype complex?

What type of inheritance does this contribute to?

A
  • due to multiple genes/loci
  • polygenic inheritance
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3
Q

What is the unabbreviated version of QTL?

A

quantitative trait loci

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4
Q

What strongly influences multifactorial characteristics?

A
  • loci
  • environment
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5
Q

What does meristic mean?

A
  • whole numbers
  • traits that are countable and can’t be continuous
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6
Q

Define threshold characteristics?

A
  • two phenotypes
  • underlying quantitative inheritance (disease susceptibility)
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7
Q

What does it mean when alleles are additive at all loci?

A
  • for every gene involved in a trait, each allele contributes a predictable amount to the overall phenotype
  • no interaction between alleles at different loci
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8
Q

Give an example of “additive, but not equal”

A

A+A+B-B- = A-A-B+B+
A+A+ does not = B+B+

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9
Q

Can environmental influences make characteristics more continuous?

A

yes

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10
Q

What does a normal distribution curve look like?

A
  • a simple hill
  • “bell-shaped”
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11
Q

What does a skewed distribution curve look like?

A

large hill, then decrease in hill height

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12
Q

What does a bimodal distribution curve look like?

A
  • two hills
  • one large, one medium
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13
Q

For normal distribution, what is the “mean”?
What’s its unit?

A
  • average
  • (line over) X
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14
Q

What is standard deviation (s)?

A
  • calculated from the variance
  • measuremnet of how far the typical individual is from the mean
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15
Q

What does it mean when the value are high for standard deviation?
Low?

A

high:
- wide curve

low:
- narrow curve

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16
Q

How do you calculate variance form standard deviation (s)?

A

variance = (standard deviation)^2
= s^2

17
Q

What does correlation measure?

A

how strongly the values of two different quantitative characteristics relate to each other

18
Q

What does it mean when the correlation value is 1?
0?
-1?

A

1:
- perfect correspondence (one is perfectly proportional to the other)

0:
- no correspondence (no relation between the two characteristics)

-1:
- perfect correspondence (inversely proportional)

19
Q

What does it mean when the correlation between parental values and offspring is high?

A
  • higher genetic contribution to the characteristics
  • lower environmental contribution
20
Q

What does regression measure?
What is it used for?

A
  • how two characteristics relate to each other
  • predict the actual value of one characteristic, given the value of the other
21
Q

What is regression coefficient?

A

the slope of the regression line

22
Q

What is the formula that corresponds to population variance?

A

Vp = Vg + Ve + Vge

23
Q

Within the population phenotypic variance function Vp = Vg + Ve + Vge, what is Vg?
Ve?
Vge?

A

Vg:
- genetic variance
- all different contributions to phenotype

Ve:
- environmental variance
- contribution of environmental factors to phenotypic variance

Vge:
- genetic-environmental interaction variance
- contributes to phenotypic variance
- environment factors may have different effects on genotypes

24
Q

What are the components of genetic variance (Vg)?

A

Vg = Va + Vd + Vi

25
Q

Withing the genetic variance formula (Vg = Va + Vd + Vi), what is Va?
Vd?
Vi?

A

Va:
- additive variance
- genetic component of phenotypic variability at a loci
- phenotype of Aa may be the average of AA and aa

Vd:
- dominance genetic variance
- Aa may not be the average of AA and aa

Vi:
- genic interaction variance
- alleles at different loci may interact and not be additive

26
Q

What does the phenotypic variance formula look like when Vg is substituted with its components?

A

Vp = (Va + Vd + Vi) + Ve + Vge

27
Q

Whar are the two types of heritability?

A
  • broad-sense heritability
  • narrow-sense heritability
28
Q

What does it mean when broad-sense heritability is equal to zero?
1?

A

0:
- no genetic component
- all phenotypic variation is environmental
- offspring would resemble their parent similar as a stranger would

1:
- genetic component completely accounts for all phenotypic variance
- offspring will resemble parents exactly

29
Q

What is commonly the value of broad-sense heritability?
What does this mean?

A

0.5

  • genetic and environmental components of variance are similar magnitudes
30
Q

What is the formula for broad-sense heritability?
narrow-sense heritability?

A

broad:
H^2 = Vg/Vp

narrow:
h^2 = Va/Vp

31
Q

What is the difference between broad-sense heritability and narrow-sense heritablility?

A

broad:
- includes all genetic components

narrow:
- includes just additive and phenotypic variance

32
Q

What is narrow-sense heritability used for?

A

predicting the inheritance of quantitative traits

33
Q

Why can’t you eliminate environmental variance by growing/raising individuals in identical environments?

A

it is impossible for two environments to be exactly the same

34
Q

What is one way to eliminate genetic variance (Vg)?
What would be the new phenotic variance formula?

A
  • inbreeding or cloning individuals

Vp = Ve

35
Q

What is another formula for broad-sense heritability?

A

H^2 (varying population) = (Vp (varing population) - Vp (identical population)) / Vp (varying population)

36
Q

What is artificial selection applied to?

A

members of a parental population

37
Q

What is the formula for narrow-sense heritability (h^2)?

A

h^2 = R/S

38
Q

Within the formula for narrow-sense heritability (h^2) (h^2 = R/S), what is R?
S?

A

R = response to selection = x (original) - x (offspring)

S = selection differential = x (original) - x (selected)