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Genetics > Exam 3: Quantitative Genetics and Complex Disease I > Flashcards

Exam 3: Quantitative Genetics and Complex Disease I Flashcards

1
Q

quantitative genetics

A

deals with phenotypes that vary continuously (e.g characters such as height or mass) -as opposed to discreetly identifiable phenotypes and gene products (such as bristle number in flies, or presence of a particular biochemical)

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2
Q

discontinuous (qualitative) traits

A

posses only a few phenotypes (e.g. red or white petals)

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3
Q

continuous (quantitative) traits

A

characteristics vary along a scale of measurement with many overlapping phenotypes (ranges from a low to a high and everything in between)

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4
Q

GWAS

A

a genome-wide association study is an examination of many common genetic variants in different individuals to see if any variant is associated (co-segregates) with a trait

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5
Q

DGAT1-2

A

single gene with a big impact; catalyzes the final step of oil synthesis

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6
Q

polygenic inheritance

A

occurs when one characteristic is controlled by 2 or more genes. often genes are large in quantity but small in effect. (ex height, skin color, and weight) many genes contribute to a phenotypic outcome

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7
Q

all of the traits Mendel studied were

A

discontinuous

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8
Q

what would have happened if Mendel studied traits with a continuous phenotypes?

A

mendel would not have been able to come to the mathematical conclusions that he did; results would have been difficult to interpret

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9
Q

t/f: in the real world, rare that alleles have an equal contribution

A

true

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10
Q

t/f: if we are trying to understand the genotype of a particular phenotype, each can have a different genotype but still same phenotype

A

true; for a quantitative characteristic, each genotype may produce a range of possible phenotypes

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11
Q

quantitative characteristics (5)

A
  1. exhibit complex relationships btwn genotype and phenotype
  2. are likely polygenic
  3. may have important environmental influences
  4. phenotypic ranges may overlap
  5. cannot use standard methods to analyze
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12
Q

height is a continuous variable and factors that regulate height is

A

very complicated; lots and lots of small contributions from multiple genetic variants

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13
Q

types of quantitative characteristics (2)

A
  1. meristic characteristics

2. threshold characteristics

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14
Q

meristic characteristics

A
  • determined by multiple genetic and environmental factors, and can be measured in whole #s
  • animal litter size
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15
Q

threshold characteristics

A
  • measured by presence or absence

- susceptibility to disease

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16
Q

threshold characteristics display

A

only 2 possible phenotypes (the trait is either present or absent) but they are quantitative bc the underlying susceptibility to the characteristic varies continuously

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17
Q

when the susceptibility exceeds a threshold value:

A

the characteristic is expressed

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18
Q

susceptibility to disease

A

threshold characteristics (mild response to a disease to having all the symptoms) a certain combination of genes can exceed a threshold and make you senstive to disease

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19
Q

the danger of exceeding a threshold

A

as you accumulate genetic variants, you accumulate genes that make you more susceptible to disease

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20
Q

polygenic inheritance

A
  • refers to quantitative characteristics controlled by cumulative effects of many genes
  • each character still follows Mendel’s rules
  • may be influenced by environmental factors
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21
Q

as the number of loci affecting the trait increases,

A

the number of phenotypic classes increases

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22
Q

distribution (2)

A
  • frequency distribution

- normal distribution: a symmetrical (bell-shaped) curve

23
Q

sample definition

A

a REPRESENTATIVE small collection of individuals from the population

24
Q

population definition

A

a group of individuals of interest

25
what is a population
ALL MEMBERS OF A PARTICULAR GROUP (people who live to be 100 yrs old)
26
what is a sample
A SUBSET OF THE POPULATION THAT SHOULD BE REPRESENTATIVE OF THE LARGER POPULATION
27
how do we ensure that a sample set is representative of a population?
draw at random = truly representative of the population
28
a frequency distribution is a graph that displays
the # or proportion of different phenotypes
29
t/f: distributions of phenotypes can assume several different shapes
true
30
a distribution with 2 peaks is
bimodal (probably reflects some environmental selection as seen in skewed distributions as well)
31
mean
average of a set of values
32
variance
the variability w/in a group of measurements
33
standard deviation
the square root of the variance
34
mean provides information about
the center of a distribution.
35
variance provides information about
the variability of a group of phenotypes
36
the variance =
the standard deviation squared (sd^2)
37
1 SD = | 2 SD =
1 SD = 66% of the sample | 2 SD = 95% of the sample
38
correlation
when 2 characteristics are correlated, a change in one characteristic is likely to be associated with a change in the other
39
correlation coefficient (r)
a statistical measure of the strength of association
40
what does correlation demonstrate?
CORRELATION DOES NOT DEMONSTRATE A CAUSE-AND-EFFECT RELATION. it simply means that a change in a variable is associated with a proportional change in the other variable
41
the correlation coefficient describes the relation btwn
2 or more variables
42
a perfect correlation will have a correlation coefficient of
1
43
a negative coefficient indicates an
inverse relationship
44
the greater the variance, the _
more spread out the distribution is about the mean (ex s^2=4.0)
45
small standard error means
there is little variance (s^2=0.25)
46
t/f: a correlation coefficient can be computed for a single variable measured for pairs of individuals
true
47
regression
predicting the value of one variable, if the value of the other is given
48
regression coefficient
represents the slope of the regression line, indicating how much one value changes on average per increase in the value of another variable
49
a regression line defines the
relation btwn 2 variables; the regression line is the line that best fits all the points on the graph
50
the regression coefficient represents the
slope of the regression line
51
the regression coefficient, b, represents the
change in y per unit change in x
52
when the regression coefficient is 1, a
1-unit increase in x is associated with a 1-unit increase in y
53
when the regression coefficient is 0.2, a
1-unit increase in x is associated with a 0.2-unit increase in y

Genetics (37 decks)

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