breeding exam 3 multiple choice

heritability, ease of measurement, genetic correlation to other economically important traits, economic importance

what four things should be known about a trait before it is included in a selection program?

migration is?

movement of individual animals into or out of, a population

breeding to a common ancestor, breeding success, lethal, and sublethal, eliminating phenocopies as a potential cause

discovering and identifying genetic defects is usually the result of?

Milk production in dairy cattle or any repeated trait

A Permanent Environmental Effect (like losing function in half the udder), would impact which of the

following traits?

Bbccddeeffgg

if you were looking at the following 6 locus genotypes, which would you expect to breed the bull's progeny difference (PD) for yearling weight?

125

if a bull had a BV of 250 for YW, what would the bull's PD be for YW?

hardy- weinburg- equilibrium

what best describes the following statement: " in the absence of selection, mutation, migration, and random drift, the gene and genetyoic frequencies of a herd of random mating livestock should never change"

DNA tests for recessive alleles

what of the following DO NOT influence the effectiveness of selection?

20600

if a population of holstein cows has and average level if milk production of 20000 lbs. one cow in the population has a G value of +750 and an E value of -150. what is her expected level of production

225

if a holstein bull is mated to a large number of randomly delected dairy cows. on average, the female offspring resulting from these matings produced 225 lbs. more milk oper lactation than the average dairy cow.what is the sire's PD for milk production?

BV

as animal breeders, we should select replacements with the best?

threshold traits

polygenic, quantitative traits that follow a normals distribution but with regard to genetic prediction, we draw a point at which they exhibit the desired phenotype or if they fall below they exhibit the other phenotype. EPDs for these traits are often expressed as percentages

a DNA test

determine if ____ is available for a trait before investing the time to do rest matings to determine genotype

it would increase the frequency of n ober time in population1

if N= normal development and n=lethal recessive gene which results in homozygous recessive genotypes being born dead. if Nn genotypes have an advantage in fitness over NN genotypes , what impact would it have on the gene frequency of the n allele ove time in this populatuon?

AA and Aa

If one locus has two alleles A & a. Independent, additive effects on marbling score are A = 1 & a = -1,

furthermore A is completely dominant to a. So the Genotypic Value, Breeding Value and Gene

Combination Values are shown in the table below:

Genotype

AA

Aa:

BV G

2

0.

2

2

GCV

0

2

0

a a

-2 -2

What genotypes should result in the highest level of marbling?

AA

If one locus has two alleles A & a. Independent, additive effects on marbling score are A = 1 & a = -1,

furthermore A is completely dominant to a. So the Genotypic Value, Breeding Value and Gene

Combination Values are shown in the table below:

Genotype

AA

Aa:

BV G

2

0.

2

2

GCV

0

2

0

a a

-2 -2 If your breeding objective is to increase marbling, what genotype should you select?

you need to select for a homozygous dominant (NN) or a clean sire in order for the lethal allele to not manifest

You own an outstanding ewe flock and recently discovered they ALL are carriers of a lethal recessive

gene. N is the allele that leads to normal development and n is the lethal recessive allele which results in

homozygous recessive genotypes being born dead. You are currently in the process of selecting a new

herd sire. What is the genotype you need in your next stud ram that will permit you to capture the

genetic value of these breeding females while NEVER permitting the lethal recessive to manifest itself?

DD= 0.24

Dd= 0.62

dd= 0.14

You found two breeds of cattle that complement each other quite well and decided to mate them to

generate Fl crossbred offspring.

Frequencies of a pair of alleles at a locus of interest in the two populations are:

Population 1 D = 8 and d = .2

Population 2 D = 3 and d = .7

a. What will be the genotypic frequencies at this locus in the F1 population?

p= 0.24 + 1/2 0.62 = 0.55

q= 0.14 + 1/2 0.62 = 0.45

You found two breeds of cattle that complement each other quite well and decided to mate them to

generate Fl crossbred offspring.

Frequencies of a pair of alleles at a locus of interest in the two populations are:

Population 1 D = 8 and d = .2

Population 2 D = 3 and d = .7

What will be the gene frequencies at this locus in the F1 population?

Dd

You found two breeds of cattle that complement each other quite well and decided to mate them to

generate Fl crossbred offspring.

Frequencies of a pair of alleles at a locus of interest in the two populations are:

Population 1 D = 8 and d = .2

Population 2 D = 3 and d = .7

Which genotype should have the most hybrid vigor?

DD= 0.3025

Dd= 0.495

dd= 0.2025

You found two breeds of cattle that complement each other quite well and decided to mate them to

generate Fl crossbred offspring.

Frequencies of a pair of alleles at a locus of interest in the two populations are:

Population 1 D = 8 and d = .2

Population 2 D = 3 and d = .7The F1 population turned out to be so exceptional, you decided to randomly mate them to create an F2

generation. What will be the resulting genotypic frequencies in the F2 population?

0.3025 + 1/2 0.495= 0.55

0.2025 = 1/2 0.2025= 0.45

You found two breeds of cattle that complement each other quite well and decided to mate them to

generate Fl crossbred offspring.

Frequencies of a pair of alleles at a locus of interest in the two populations are:

Population 1 D = 8 and d = .2

Population 2 D = 3 and d = .7

What will be the gene frequencies in the F2 population?

the number of heterozygotes decreased, the number of homozygotes increased, adn heterisus decreased

You found two breeds of cattle that complement each other quite well and decided to mate them to

generate Fl crossbred offspring.

Frequencies of a pair of alleles at a locus of interest in the two populations are:

Population 1 D = 8 and d = .2

Population 2 D = 3 and d = .7

What changed in the F2 generation?

there is no change in the gene frequency therefore, to increase hybris vigor, you must introduce anpther population of breed

You found two breeds of cattle that complement each other quite well and decided to mate them to

generate Fl crossbred offspring.

Frequencies of a pair of alleles at a locus of interest in the two populations are:

Population 1 D = 8 and d = .2

Population 2 D = 3 and d = .7

What is the downside of this change?

q= 0.5 (d)

p=0.5 (D)

You own 300 Hereford cows. Upon taking inventory of the Horned/Polled phenotype in you cow herd,

you have 75 cows that are horned. D is the dominant, polled allele and d is the recessive horned allele.

a. What are the gene frequencies of D and d in your cow herd?

DD=.25

Dd=.50

dd=.25

300 x .5= 150 polled cows are carriers

You own 300 Hereford cows. Upon taking inventory of the Horned/Polled phenotype in you cow herd,

you have 75 cows that are horned. D is the dominant, polled allele and d is the recessive horned allele.

How many polled cows are horned gene carriers in this herd?

Expected genotypic frequency of homozygous polled cows = 0.25 (25%)

You own 300 Hereford cows. Upon taking inventory of the Horned/Polled phenotype in you cow herd,

you have 75 cows that are horned. D is the dominant, polled allele and d is the recessive horned allele.

What is the expected genotypic frequency of homozygous poled cone

if you mate carriers to carriers, 25% of the offspring will be born dead

At a particular locus, if the N allele leads to normal development and the n allele is a lethal recessive

which results in homozygous recessive genotypes being born dead. What is the expected percentage of

dead offspring if you mate "carriers" to "carriers'?

0.5

You are a purebred cattle breeder and have a herd of 100 purebred cows. Recently your breed

association informed you that a sub-lethal genetic abnormality had been identified that is caused by a

recessive allele. Your entire cow herd traces back to a known carrier of the allele causing the genetic

abnormality. All your cows are also bred to bulls which you raised that also trace back to a known

carrier of the genetic abnormality. After calving you identify 25 calves that exhibit the abnormal

phenotype. What is your best estimate of the frequency of the sub-lethal allele in your herd?