Genetics and Animal breeding deck 1 Flashcards
1
Q
Define a population.
A
a group of individuals of one species that inbreed in the
same place, at the same time, and are isolated from other groups of the same species.
A “basic unit of evolution”.
2
Q
A term for an association of different organisms forming a closely integrated community.
A
biocoenosis
3
Q
A species becomes separated into distinct populations due to what key factors that drive evolution?
A
genetic variation between individuals,
natural selection,
isolation.
4
Q
term for random mating
A
panmixia / panmixis
5
Q
When is a population referred to as closed?
A
mating with individuals from other populations
does not occur
6
Q
define gene pool
A
The sum total of all alleles (collective genetic information) carried in all members of a population.
7
Q
what is population size denoted as?
A
N
8
Q
what is a sample of a population denoted as?
A
n
9
Q
another term for random
A
stochastic
10
Q
The probability of an event is a ratio that is given as?
A
a numerical value between zero and one.
11
Q
The probability of a sure event is?
A
1
12
Q
The probability of an impossbile event is?
A
0
13
Q
What is the multiplication rule?
A
Given the probabilities of two independent events (A and B), the rule states that the probability that both events occur is found by multiplying the probabilities of the events.
p(AB) = p(A) x p(B).
14
Q
How are different genotype-numbers denoted?
A
D
H
R
15
Q
How are genotype frequencies denoted?
A
d
h
r
16
Q
How is d calculated?
A
d = D/N
17
Q
How is h calculated?
A
h = H/N
18
Q
How is r calculated?
A
r = R/N
19
Q
d + h + r = ?
A
always 1
20
Q
The sum of genotype frequencies always equals?
A
1
21
Q
Based on what info can absolute counts of alleles in the
population be calculated
A
Based on the numbers of individuals with different genotypes
22
Q
What does P denote?
A
absolute count of dominant allele
23
Q
What does Q denote?
A
absolute count of recessive allele
24
Q
How is absolute count, P calculated?
A
P = 2D + H
25
How is absolute count, Q calculated?
Q = 2R + H
26
How is frequency of recessive allele denoted?
q
27
How is frequency of dominant allele denoted?
p
28
What is the Hardy-Weinberg principle?
the concept that in a panmictic population in genetic equilibrium - gene and genotype frequencies will remain constant from generation to generation.
29
What is the Hardy-Weinberg formula/equation?
p2 + 2pq + q2 = 1
where
p2 is BB
2pq is Bb
q2 is bb
30
direct mutation is?
Change of the allele from normal to mutant
31
reverse mutation is?
change of the mutant allele to normal
32
The frequency of direct mutations is typically
| designated by the letter
u
33
The frequency of reverse mutations is typically
| designated by the letter
v
34
Define mutability
is the mutation rate of genes.
The mutability of genes varies between different loci.
35
what is mutation pressure
the intensity of the occurrence of mutations
36
What is mutation pressure dependent on?
the ratio between of the direct and reverse mutations in a
| population.
37
Selection coefficient (s) is?
a measure of the relative reduction in the contribution a particular genotype makes as compared with another genotype in the population.
38
If one of the three genotypes (AA, Aa, aa) is completely removed from a generation, this genotype has a selection coefficient of?
s = 1
39
in case of the maximum relative contribution of a genotype to the next generation (none of the animals
possessing a given genotype have been removed), the selection coefficient would be?
s = 0
40
What does W denote
the selection value or fitness of all the remaining animals is expressed by W
41
selection efficiency (Δq) is?
The change in gene frequency in the next generation
42
selection efficiency indicates
the rate of improvement in performance (removal of undesirable genes) from selection during a generation.
43
define random gene drift
the change in the frequency of an existing gene variant in a population due to random chance.
44
define the concept of effective population size
The number of individuals that effectively participates in producing the next generation
45
how is effective population size denoted
Ne
46
Genetic relationship between individuals X and Y can be measured by calculating
the relationship coefficient (Rxy).
47
the relationship coefficient (Rxy) measures
Rxy demonstrates the relative similarity of the genotypes of the two related individuals.
48
The coefficient of inbreeding is denoted?
(Fx)
49
define heterosis
or 'hybrid vigor', or 'outbreeding enhancement'
is the improved or increased function of any biological quality in hybrid/heterozygous offspring.
50
name two phenomenon that result in change in the proportion of homozygotes and heterozygotes in a population.
Heterosis and inbreeding depression
51
explain the dominance hypothesis
Heterozygosity will increase in the offspring obtained by crossing homozygous individuals, whereas the offspring can have more dominant genes than either parent.
AA = Aa > aa
52
explain the overdominance hypothesis
Overdominance is a condition when the heterozygote is greater in phenotypic value than either homozygote.
AA < Aa > aa
53
What basic parameters do the genetic properties of a population depend on?
on gene and genotype frequencies
54
What is The phenotypic value of an individual
is the numerical value obtained by measuring a certain phenotypic trait.
55
To analyse the genetic properties of a population, what should be done?
the factors affecting the phenotypic values of individuals shall be determined.
56
phenotypic value is denoted?
Pi
57
genotypic value is denoted?
Gi
58
the phenotypic value/formula can be expressed as:
Pi = Gi + E
E being environmental factors
59
Which 3 factors affect the average genotypic value of a population?
gene dominance
gene frequency
gene value
60
define breeding value
(BV) of an individual is the sum of the mean value of genes or additive genetic value of the individual.
Breeding value is an expression of the genetic potential for increased productivity of an animal.
61
breeding value of an individual is denoted?
A
62
How is heritability denoted?
h2
63
What is heritability
The ratio of the genotypic variance to phenotypic variance
64
how much would low heritability be
h2 < 0.3
65
how much would medium heritability be
h2 = 0.3 to 0.6
66
how much would high heritability be
h2 > 0.6
67
define pleiotropy.
occurs when one gene influences two or more seemingly unrelated phenotypic traits. Such a gene that exhibits multiple phenotypic expression is called a pleiotropic gene.
68
Correlation analysis describes
the strength and direction of the relationship between traits.
69
What does BLUP stand for?
Best Linear Unbiased Prediction
70
What is the BLUP method?
Best Linear Unbiased Prediction is a standard method for estimating random effects of a mixed model.
originally developed in animal breeding for estimation of breeding values and is now widely used in many areas of research.
71
Farm animal selection is aimed at?
increasing the frequency of genes that determine the desired traits in a population.
72
The traits appropriate for selection should comply with what 3 criteria:
1) trait must be heritable
2) trait must be variable
3) trait must have an economic value.
73
Tandem selection means
that selection criteria are changed after one or a few generations.
74
Conventional tandem selection means
that selection focuses on one trait until a desired level is reached (several generations), then another trait will be in focus.
75
explain Independent culling levels -method
where minimum standards of performance are
| established for each trait in the criteria. Those animals who do not qualify with the minimum, are culled.
76
explain selection index -method (SI)
where the net values of all traits of the selection criteria are combined into a single index value.
Selection is then based on the ranking of individuals according to index value and those with the greatest values are selected.
77
The single index value is derived utilizing what 3 criteria?
the heritabilities of the traits,
correlation among traits,
and economic value of each trait.
78
What is the major criterion for evaluating breeding programmes.
Predicted selection response (R)
79
If heritability is 0.3, how much influence do environmental factors have (expressed in %)
h2 = 0.3 = 30%
so 70% is up to environment
80
mean Pp
average phenotypic value of the selected parents of the next generation
81
mean P
average phenotypic value of the initial population
82
mean Po
average phenotypic value of the offspring population
83
h2 =
R / SD
84
R =
h2 x SD
85
"phenotypic variance of a trait in a population" is denoted?
sigma squared p
86
define selection intensity and how it it denoted?
SD is usually expressed in the units of phenotypic standard deviation of a particular trait. This kind of
a standardized selection differential is referred to as selection intensity (i).
87
phenotypic standard deviation denoted
sigma p
88
what is L?
generation interval
is the average age of parents when the offspring destined to replace them are born.
89
what is R?
selection response
90
what is i?
selection intensity
91
what is SD?
either selection differential or standard deviation
92
SD is the same as
i x sigma p
93
Name 3 types of selection depending on breeding goal
stabilizing selection,
disruptive selection,
directional selection
94
describe Stabilizing selection
Individuals that display an average phenotypic trait are selected.
Individuals that display extreme traits (+ or -) are culled.
95
describe Disruptive Selection
Individuals that display either extreme are selected. Population shifts away from the average trait, towards both extremes.
96
describe Directional Selection
This is the most frequently used method in animal breeding.
Individuals that display an “extreme” trait are selected for. Other individuals are selected against.
Population shifts toward this trait (+ or -), away from the opposite. The average phenotypic value for a trait of the offspring differs from that of the parental generation.
97
What is R?
denotes selection response - is an expression of the shift in the average phenotypic value of a population within one generation or over a certain period of time.
98
The ratio of the selection response and the selection differential is heritability. whats the formula for this
h2 = R / SD
| R = h2 x SD
99
reduction of body weight formula and explain components
y = a + b multiplied by x
```
where
y = reduced body weight
a = intercept
b = regression coeff. for weight/age
x = age in days
```
100
relationship coefficient formula
Rxy = 0.5 to the power of n1 + n2 ...
101
inbreeding coefficient formula
Fx = 0.5 to the power of n1 + n2.. + 1
102
how to calculate p when you do not have known frequencies but you do have absolute numbers
p = 2D + H / 2N
103
how to calculate p when you have known genotype frequencies
p = d + h / 2
104
how to calculate q when you do not have known frequencies but you do have absolute numbers
q = 2R + H / 2N
105
how to calculate q when you have known genotype frequencies
q = r + h / 2
106
what is inbreeding
Inbreeding is the mating of individuals which are more closely related than are average members of a breed or population.
107
Inbreeding depression is a term used to describe?
the unfavorable changes resulting from inbreeding, such as decrease in the performance of inbreds, most noticeably in fertility and hardiness, genetically defective offspring, etc.
108
Active inbreeding is?
may occur if animals belonging to a genetically related group are bred to each other, and the probability of recombined genes in the resulting offspring is considered to be lower than expected.
109
Passive inbreeding is?
may occur in a small population where a very small number of animals increases the opportunity for loci in the offspring to become homozygous.
110
How does inbreeding affect genotype frequencies in a population?
Inbreeding increases the homozygosity of a population.
111
𝝙F represents?
the "drift" (change) in inbreeding coefficient. Generally a change that sees increase in homozygosity.
NB! 𝝙F is also used to represent endangered status as a percentage
