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College > Animal Breeding and Genetics Test 3 > Flashcards

Animal Breeding and Genetics Test 3 Flashcards

1
Q

simply inherited traits

A

traits affected by only a few genes
coat color, horns, etc
can be qualitative or categorical
example either/or expression - black or red, horned or polled
rarely quantitaitve - measures with numbers or continuous - white spotting in cats (1-9 numerical rating)
typically affected very little by environment

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2
Q

polygenic traits

A

affected by many genes with no gene having an overriding influence
typically quantitaative or continuous in expression - phenotypes are usually described by numbers
greatly influenced by environment - lack of feed, heat/cold stress
some polygenic traits have categorical phenotypes - threshold traits - pregnancy, dystocia, natural gait

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3
Q

which traits are more important

A

typically polygenic traits - growth rate, fertility, milk production
but some markets are more sensitive to simply-inheritied traits - coat or feather color, polled, genetic defects are usually simply-inherited

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4
Q

principles of selection and mating apply to both

A

attempt to increase the frequencies of favorable alleles

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5
Q

the more genes involoved, the more ________ it is to observe the effects of individual genes, and therefore the less specific info we have about those genes

A

difficult

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6
Q

when a few or one gene affects a trait, the effects of those genes are

A

well understood

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7
Q

test matings

A

matings designed to reveal the genotype of an individual for a small number of loci
simply inherited traits

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8
Q

an individual that is Aa will produce gametes

A

1/2 will contain A and the other 1/2 will contain a
when populations are small, there may not be exactly half of each

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9
Q

three types of mating to heterozygous from greatest to least

A

mating to recessives
mating to heterozygotes
mating a sire to his daughters

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10
Q

statistic

A

estimate of a parameter

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11
Q

parameter

A

a value that describes a population

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12
Q

population

A

all the members of a group

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13
Q

sample

A

subset of a population

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14
Q

two types of variables

A

discrete - has distinct classes - ex. number of lambs born
continuous - for any two values, there is a possible intermediate value - ex. weaning weight, yearling weight

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15
Q

two basic types of statistics for a single variable

A

measures of central tendency
measures of variability

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16
Q

measures of central tendency

A

mean/average
median - number in the middle
mode - most frequent value

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17
Q

measures of variability

A

standard deviation
variance
coefficient of variation

18
Q

standard deviation

A

a measure of how widely distributed the oberservations are around the mean
symbolized with a small s or sigma

19
Q

variance

A

the square of the standard deviation
sybolized with either an s quared or sigma squared
relatively little value by itself

20
Q

coefficient variation

A

the standard deviation as a percent of the mean
useful for comparing the relative amounts of variation for various traits

21
Q

what two statistics are useful in determining if a relationship exists

A

correlation
regression

22
Q

correlation

A

the measure of the association between two variables
values from -1 to 1

23
Q

regression coefficient

A

a measure of the linear relationship between x and y
the y variable is the dependent variable - its value os dependent upon the value of x

24
Q

the intercept

A

represents the value of y when x = 0
point at which the line crosses the vertical axis when the regression line is plotted

25
Q

quantitative traits

A

weights
heights
litter size
number of eggs
racing speed
controlled by many pairs of genes

26
Q

genetic effects can be divided into

A

additive effects - only effects that are heritable
dominance effects
epistatic effects

27
Q

the environmental component can also be subdivded into

A

temporary environment effects
permanent environment effects

28
Q

temporary environment effects

A

these are sources of environmental variation that have somewhat of a temporary effect
low levels of disease
moderate weather changes - heat wave
changes in management of animals - off feed

29
Q

permanent environment effects

A

change the way an animal performs for the rest of its life
failure to have acalf
severe illness
injury to udder

30
Q

heritability

A

the proportion of the phenotypic variation which is due to additive gene
the most important single concept in animal breeding

31
Q

heritability is not a constant…

A

varies from herd to herd
varies within a herd if management changes

32
Q

heritability traits and magnitude

A

reproductive - low (<0.20)
growth - moderate (0.20-0.40)
carcass - high (>0.40)

33
Q

much easier to show selection progress for _________ and _________ traits for ________ traits

A

growth
carcass
reproductive

34
Q

the importance of reproductive traits compensates for the ____________

A

low heritability
should be included in most selection programs

35
Q

repeatability

A

the association between two records on an individual
values range from 0 - 1
1 means that two records will be exactly the same
0 means that one record has no relationship to another or successive records

36
Q

permanant environmental effects are those that affect the animal ____________________

A

for the remainder of its life

37
Q

Repeatability is always at least as _________ as heritability

A

large

38
Q

phenotypic correlation

A

association between actual performance for two traits
has both a genetic and environmental contribution

39
Q

genetic correlation

A

association between genetic merit for two traits
some genes contribute to more than one trait

40
Q

genetic correlation allows us to

A

evaluate “indirect” effects of selection

College (8 decks)

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