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Bio 97 > Midterm 4 > Flashcards

Midterm 4 Flashcards

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Biology 101 flashcards
1
Q

what is limited and has competition

A

RESOURCES–> resources are limited; there is competition for those resources

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2
Q

what changes over time?

A

the distribution of alleles and genotype changes over time

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3
Q

Population genetics aim to …

A

make quantitative predictions and provide mathematical insights into the dynamics of allele frequencies and genotype frequencies in populations

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4
Q

what is a population

A

group of organisms of the same species living in the same geographical area

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5
Q

what is a gene pool

A

all alleles in population

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6
Q

genotype frequency

A

proportion of individuals in a population with a specific genotype

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7
Q

allele frequency

A

proportion of alleles in a population

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8
Q

genotype frequency does NOT equal

A

allele frequency

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9
Q

when does allele frequency equal genotype frequencies?

A

Bacteria
There is no homozygous or heterozygous
One allele for each gene
X-linked gene
Homozygous

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10
Q

one gene has how many alleles

A

one gene haas 2 alleles

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11
Q

p and q are what ??

A

shorthand notation for allele frequencies

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12
Q

what is the Hardy-Weinberg Equation?

A

p^2+2pq+ q^2= (p+q)^2=1

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13
Q

from generation to generation what doesnt change

A

allele frequencies and genotype frequencies

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14
Q

what are the hardy Weinberg conditions

A
  1. migration in/out is absent (no gene flow)
  2. Large population (no genetic drift)
  3. No mutations
  4. Equivalent viability and fertility (no selection)
  5. Mating is random
  6. Same allelic frequencies in men and women
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15
Q

hardy weinberg conditions are…

A

rarely met but helps us learn why allele frequencies change –> often met “close enough” mating is random for most genes

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16
Q

what is p^2

A

AA genotype frequency

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17
Q

what is 2pq

A

Aa genotype frequency

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18
Q

what is q^2

A

aa genotype frequency

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19
Q

what does the p and q in this relate too –> (p+q)^2

A

p is the A frequency
q is the a frequency

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20
Q

what will all genotype and allele frequencies add up too

A

always add up to 1 whether or not the population is in HW

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21
Q

if we know genotype frequencies in a population, when can we calculate corresponding allele frequencies?

a) if population is in HWE
b) if we know allele frequency of one of the allele
c) if population is not in HW equilibrium
D) any of the above

A

D) any of the above

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22
Q

if we know GF’s in a population, then we can always ….

A

calculate AF’s whether or not the population is in HW equilibrium

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23
Q

if we know Af;s we can only calculate…

A

GF’s if the population is in HW equilibrium and autosomal locus has two alleles

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24
Q

If we have X-linked recessive a allele, genotype frequencies among males are the same as allele frequencies:

A

Frequency of XaY males = p
Frequency of XaY males = q

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25
Q

forces that can cause deviation from HW ratios

A
  1. gene flow (migration)
  2. genetic drift (small population)
  3. Muations
  4. Selection
  5. Inbreeding
  6. Different allelic frequencies in males and females
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26
Q

Which of these forces does not
contribute to Evolution?
1. Gene flow
2. Genetic drift
3. Mutations
4. Selection
5. Inbreeding
6. All contribute

A

6- all contribute

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27
Q

evolution=

A

long lasting changes in the gene pool due to natural selection and other forces ( mutation, drift)

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28
Q

Gene flow example

A

migration example is gene flow between human subspecies –> Neandetals which caused 2% of DNA in europeans and east asians from Neandertals alleles that are potentially adaptive

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29
Q

genetic dift?

A

random events that can result in very good dominant allele being eliminated from the population

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30
Q

the vast majority of good alleles/genes that arose during our evolution …

A

did not end up in our gene pool

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31
Q

two types of genetic drift

A

bottleneck effect and founders effect

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32
Q

example of bottle neck effect

A

northern elephant seal population
Hunted to near extinction
* Population decreased to 20 individuals in 1800’s.
* Those 20 repopulated so today’s population is
~30,000
* Very low level of genetic variation

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33
Q

founders effect

A

when smalll group from population migrate to form new population

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34
Q

example of founders effect in human population

A

–> Old Order Amish populations are derived from a few dozen colonists who escaped religious persecution in Germany in 1719 to
settle in Pennsylvania.
* The community is closed.
* Allele and genetic disease frequencies in Amish are significantly different from the German ancestral and the surrounding local populations.

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35
Q

a random mutation is …

A

far more likely to harm the function of a protein than to enhance it

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36
Q

if mutations was the only force operating on the gene pool, then eventually

A

most alleles would become nonfunctional

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37
Q

how many bad (lethal) recessive mutations an average person carries?

A

1-2

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38
Q

Humans carry on average one to two mutations that, if inherited from both parents, can cause…

A

severe genetic disorders or death before reaching
reproductive age

39
Q

Natural selection

A

more organisms are produces each generation than can survive and reproduce

Organisms differ in their ability to compete, based
(in part) on their genotype
*Hence, genotypes that promote
survival/reproduction are favored, and are more likely to contribute alleles to the next generation’s gene pool

40
Q

forces that keep bad alleles in gene pools despite natural selection

A
  1. delayed age of disease onset
  2. slow selection against recessive alleles
  3. mutation selection equilibrium
  4. heterozygote superiority
41
Q

in haploid organisms selection is ____-

A

efficiennt

42
Q

why are haploid organism’s selection efficient

A

No recessive/dominant alleles means that a very weak selective advantage can quickly lead to a favored allele becoming fixed

43
Q

In diploids, selection for/against
recessive alleles is

A

inefficient

44
Q

why are diploids, selection for/against
recessive alleles is inefficient

A

Rare disease-causing recessive alleles
persist in the population in heterozygote carriers, even if they are lethal when homozygous

45
Q

disease incident?

A

q^2

46
Q

fraction of disease alleles in patients?

A

q

47
Q

fraction of disease alleles in carries?

A

p

48
Q

the rarer the recessive disease….

A

the greater the % of alleles that are in carries

49
Q

alleles in carries are …

A

hidden from selection

50
Q

function of selection and new mutations

A

selection = eliminates harmful alleles
new mutation = generate harmful new alleles

51
Q

describe the relationship between selection and new mutations

A

These forces push the population out of HW equilibrium, but they push in OPPOSITE directions

Over time, an equilibrium is reached where allele frequencies are stable - new alleles are removed by selection at the same rate they are created by
mutation

52
Q

bad alleles are a …

A

stable part of the gene pool

53
Q

Malaria

A

A serious, infectious disease
(~300 million annual cases; ~1 million deaths)
* Flu-like symptoms, anemia, jaundice
->kidney failure, coma, death
* Caused by infection with the parasite Plasmodium
* Transmitted by mosquito bites
* Kills Red Blood Cells and releases toxins into bloodstream

54
Q

Sickle Cell Anemia

A

-Autosomal recessive, incidence 1/500 among AA
* Gain-of-function mutation in the gene encoding the b chain of
hemoglobin → causes Hb aggregation which in turn
deforms red blood cells (RBCs)
* Sporadic vessel clotting causes acute pain, organ failure
* Shorter half-life of RBCs causes anemia

55
Q

Heterozygote Superiority
(or advantage)

A

Homozygous normal (SS)
* Reduced survival because of Malaria

Homozygous recessive (ss)
* Reduced survival because of Sickle cell anemia

Heterozygous carrier (Ss)
* Survival and reproductive advantage

56
Q

result of slow selection against recessive alleles

A

most disease causing recessive alleles are in carriers, not patients

57
Q

result of mutation-selection equilibrium

A

Result: disease-causing alleles are a stable part of our gene pool –> we’re all genetically defective

58
Q

result of heterozygote superiority

A

Result: “bad” alleles may be good in some contexts

59
Q

inbreeding affect on individual

A

Increases the risk of having a
kid homozygous for a rare recessive allele

60
Q

inbreeding affect on population

A

Results in an excess of
homozygotes compared with random
mating

61
Q

how to check for HWE

A

If a population is in HW equil., then genotype and allele freqs. should be related as follows:

AFs should correctly predict GFs
Freq (AA) = p2
Freq (aa) = q2
Freq (Aa) = 2pq

62
Q

complex or quantitative trait is a

A

measurable phenotype that depens on the cumulative actions of many genes and the environmnent

63
Q

multiple additive genes can give rise to …

A

continuous variation

64
Q

With lots of additive genes it starts to look like a…

A

normal distribution

65
Q

what are the properties of quantitative traits

A
  1. polygenic
  2. multifactoral
66
Q

polygenic?

A

variation is caused by the combined effects of multiple genes

67
Q

multifactorial?

A

variation is caused by the combined effects of genes and environments

68
Q

When considering an additive trait, the
larger the number of genes controlling
the trait, the _____ the number of
phenotypes
A. Larger
B. Smaller
C. Same

A

A) larger

69
Q

examples of quantitative/complex traits

A

height
weight
blood pressure
eye color
personality
heart disease
diabetes
alzheimers disease

70
Q

quantitative traits fit what??

A

normal distribution

71
Q

threshold trait examples?

A

autism, most birth defects
heart disease, diabetes, alzeihmer’s disease,

72
Q

threshold traits are …..!

A

multifactorial (environment matters

73
Q

Threshold traits description

A

traits that are all or none, but appear to be influenced by multiple genes and the environment.–> think diabetes bc you have diabetes only if your blood in your sugar reaches a certain threshold

74
Q

phenotypic variance is a…

A

sum of environmental variance (Ve) and genetic variance (Vg)

75
Q

Environmental variance?

A

Ve= the portion
of phenotypic variance that is due to
differences in the environments to which the individuals have been exposed.

76
Q

broad sense heritabilty?

A

H^2 is between 0 and 1 and is proportion of the total variance of a trait that is caused by genetic variation

77
Q

equation for H^2

A

H^2= Vg/ (Vg +Ve)

78
Q

H^2 is also known as

A

broad sense heritability

79
Q

how to asses environmental variance in human population

A

Comparisons of variability between
identical twins can be used to estimate
heritability

80
Q

identical twins arise from

A

the splitting of a single fertilized egg –. clones –> all alleles identical

81
Q

If there is variation in a trait between two identical twins,

A

then that variation must have been caused by environmental,
not genetic factors

82
Q

example of variation due to environment in identical twins

A

Fingerprints differ between
identical twins -> Variation in
fingerprints is due to environment

83
Q

Little variation in a trait (e.g height) between identical twins - the cause is genetic?

A

Not necessarily, because identical twins
are usually raised in a very similar
environment

84
Q

Little variation in a trait (e.g height) between identical twins - Solutions?

A

Solution 1: Compare to fraternal twins.
If variation in a trait between fraternal
twins is greater than variation between
identical twins
–> that additional variation is presumed to
be due to genetic differences

Solution 2: Use reared apart identical
twins and compare to random people

85
Q

Fraternal twins have ________ _________,
while most identical twins share______

A

Fraternal twins have separate placentas, while most identical twins share placenta

86
Q

Which of the following is TRUE about
twin studies?
A. Differences between identical twins can be
due to genes or the environment
B. Differences between fraternal twins are due
to the environment only
C. If there is a genetic component to a trait, you
would expect more variation between
identical than fraternal twins
D. If a trait has a heritability near 0, identical
twins reared apart from each other will
vary as much as two random people

A

D. If a trait has a heritability near 0, identical
twins reared apart from each other will
vary as much as two random people

87
Q

*H2 near 1.0 –>

A

identical twins will have the
same value for the trait, even if they are reared apart*

88
Q

H2 near 0 –>

A

identical twins reared apart
from each other are no more likely to have the same value for the trait than any two random people

89
Q

Vaccines do not cause….!

A

autism

90
Q

why are the genetics of autism complex?

A

identical twins reared apart
from each other are no more likely to have the same value for the trait than any two random people

PROBABLY both since many gene sare implicated in autism (some epistatic) but environment also plays a role

91
Q

concordance?

A

is the likelihood that a pair of individuals will share a trait or characteristic if one of them does.

92
Q

autism and concordance?

A

A 1977 study found 82% concordance in identical twins vs. 10% in fraternal twins.

93
Q
A

Bio 97 (4 decks)

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