ANSC 340 - Genetics Practice Final MC Section

The position on a chromosome at which a gene is located is called?

locus

Which two mechanisms contribute to genetic diversity?

meiosis and crossing over

You have decided to spend money to have all of your potential breeders tested for the presence of a lethal allele. You then breed only those who tested negative.  This is an example of :

marker-assisted selection

The mating of an individual with a dominant phenotype to one that is a known homozygous recessive is termed a?

testcross

___________ mating is the mating amongst a generation?

Inter se mating

_________ is the mating of an F1 to an individual from one or the other of the pure breeding strains used to create the F1

backcross

What is the phenotypic ratio you would expect from a dihybrid cross?

9:3:3:1

What is the simplest (3 word) explanation of Mendel’s Law of Segregation?

Alleles Sort Randomly

Mammalian gametic cells are diploid (T/F)?

False

A missense mutation is one that codes for a premature stop (T/F)?

False

Genes (and the traits they control) on sex chromosomes referred to as?

sex-linked

The failure of chromosomes to separate properly during meiosis is known as?

nondisjunction

A relatively common example of a clinical result of nondisjunction in humans is?

Down Syndrome

Calico coloring in a male cat is rare but possible. What must occur (in terms of the cat’s genotype) for a male cat to be calico?

• nondisjunction of sex chromosomes resulting in XXY

• Presence of the Spotting allele

• Mosaicism resulting from different X-inactivation in a heterozygote

Scrotal rupture in pigs, a situation where the phenotype associated with a particular genotype is not always expressed, is an example of?

incomplete penetrance

A _________ probability is the probability of 2 or more independent events occurring together?

joint

The probability that one of any number of mutually exclusive events occur is the __________ of probabilities of each event?

sum

In the horse, the mare is the homogametic sex (T/F)?

True

In the chicken, the hen is the homogametic sex (T/F)?

False

In the case of codominance and two alleles, how many distinct phenotypes are there?

3

We use a ___________ test as a means to test a genetic hypothesis?

X² (chi square)

If we fail to reject the hypothesis that two loci are independent, what can we assume about their location within the genome relative to each other?

They could either be far apart on the same chromosome or on different chromosomes

The easiest and cheapest way to avoid producing rat-tailed calves is to breed?

red to red, black to black, cream to cream

A stallion has the genotype AaBb. What are the possible recombinant genes?

Unable to determine with the information given

An AAbb stallion is mated to an aaBB mare. The offspring was found to have aB and Ab gametes. These gametes are?

parental

The term we use to denote recombination frequency is?

theta

Two loci on the same chromosome segregating together very often (there is little crossing over between the two loci). What is the possible range of theta?

 

0.00 < theta < 0.50

Recombination information can be used to construct a map of the order of loci and relative distance between loci. Maps constructed as such are referred to as ________________________maps?

linkage

A map constructed based on DNA sequence information is referred to as a ________________ map?

physical

If your chi square value is very close to your critical value, you should?

test again with more observations

f(Bb) = ?

Q

q denotes?

f(bb)

Which describes the frequency of the dominant allele within a population?

p(lowercase)

Hardy-Weinberg Equilibrium

Allelic and genotypic frequencies remain unchanged throughout generations

What must be absent in order for HWE to occur?

migration

Genetic Drift

changes in allelic and genotypic frequencies occur faster in smaller populations

The effect of a migration event on the allelic and genotypic frequencies of a population will depend largely on?

the difference in allele frequency between the native and immigrant populations

Q = q² ?

is only true in Hardy-Weinberg Equilibrium

q = Q+ ½ H?

is always true

Mutations can rapidly affect allelic and genotypic frequencies within a population (T/F)?

False

Which statement is true?

It takes only one generation of outbreeding to permanently increase heterozygosity

Black or brown coat color is an example of a _________ trait?

simply-inherited and qualitative trait

To detect a recessive allele in a possible carrier, the most efficient way would be to mate it to what type genotype of animals?

homozygous recessives

If a particular genotype is being culled out of a population, the relative fitness of that genotype is?

zero

If a particular genotype is being culled out of a population, the selection coefficient (s) for that genotype is?

one

Over-dominance is a phenomenon where?

the heterozygote genotype is the most fit

If relative fitness for the homozygous dominant, the heterozygous, and the homozygous recessive genotypes are 1.0, 0.5, and 0.0. respectively, the mode of inheritance with regards to survival is?

codominance

If relative fitness for the homozygous dominant, the heterozygous, and the homozygous recessive genotypes are 1.0, 1.0, and 0.0. respectively, the mode of inheritance with regards to survival is?

simple dominance

I'm currently listening to the soundtrack of Game of Thrones, and I am reminded of Circe's remark, "in the game of thrones, you either win or you die".  Of the original 8 members of family Stark,  4 of them survived.  In the family Lannister, out of 8, only one survived.  If the two families represented two possible genotypes at a single locus, the Starks would have a relative fitness of _______, and the Lannisters a relative fitness of __________.

1, 0.25

The regression of y on x is equal to?

the regression of x on y

b^xy is?

The regression of x on y, COV_x,y/ variance y²

Variance is?

• a required component when considering effectiveness of genetic selection

• mathematically related to STDEV

• limited as a useful term

Covariance

measures direction of a relationship ONLY

Correlation Coefficient

measures rate of change and direction of a relationship

Regression Coefficient

measures rate of change and direction of a relationship

Standard deviation

• is a measure of variation within a population

• is the square root of variance

• Marks the point of inflection on a normally distributed bell curve

r_x,y = r_{y,x (T/F)?}

False

b_x,y = b_{y,x (T/F)?}

False

Because a litter is raised by one dam, often the performance of littermates will be more alike than you would expect given the proportion of genes they have in common.  This effect, denoted by the term “c²” is known as __________________?

Common Environmental Effect

The average performance of many progeny is a good indication of an individual’s?

breeding value

An EPD based on an animal’s own data is more accurate than one based on a number of his progeny (T/F)

True

Heritability for litter size is 0.4. When computing the accuracy of an EPD for litter size, h² = ?

SQRT (0.4) = 0.63

The baseline used to compare birthweight EPDs is a standard reference number used by all beef cattle breed associations (T/F)?

False

Littermates are by default full sibs (T/F)?

False

Which statement reflects the relationships between accuracy, confidence range, and possibility change associated with an EPD?

• All three are correlated with amount of evidence

• All three are usually correlated age of the animal

• All three are correlated with heritability

When heritability is _________,

a sire’s own performance record is valuable in estimating BV for that trait

high

Possible Change represents what statistic in reference to accuracy of an estimated BV?

 

The standard deviation of true BV based on estimation

If accuracy of an EBV is calculated as “h”, then?

 

“h” is the square root of the heritability

change in BV_y|x/t = [(r_BVx,BVy)(r_BVx,BVx)i_xBVy]/L

 

Selection to improve the BV of trait X may alter the BV of trait Y

BV_y|x/t = [(r_BVx,BVy)h_xh_yi_xPy]/L

 

Is used to calculate correlated rate of progress in trait Y when using phenotypic data for trait X

r_Px,Py = r_BVx,Bvy + r_Ex,Ey

False

If  [BV_y|x/t] /[BV_y/t]  > 1.0,

the correlated response in trait Y to direct selection of trait X will be better than the response to direct selection for trait Y.

True

Selection indices should only be used to compare animals within the same or highly similar ____________.

contemporary groups

A selection index allows you to look at one or more traits and derive a comprehensive  _______ for an animal.

breeding value

Threshold traits are better selected for directly rather than by a correlated continuous trait (T/F)?

False

Bill uses a selection index based on 3 traits.  Ted uses an index based on 6 traits.  Whose index provides the greatest overall selection intensity?

Bill

A possible cause for the phenomenon of correlated traits is?

pleiotropy and linkage

Which crossbreeding system retains the most heterosis at equilibrium?

3-breed spatial rotation with crossbred sires

Which crossbreeding system retains the least heterosis at equilibrium?

 

2-breed spatial rotation with purebred sires

Which terminal cross results in the most heterosis in the market offspring?

 

Composite male x F1 Yorkshire x Landrace female

If a crossbred progeny does not perform better than both of its purebred parents, it does not exhibit heterosis (T/F)?

False

Percent Maximum Heterosis in F1 progeny?

100%

Percent Maximum Heterosis in F2 progeny?

50%

Percent Maximum Heterosis in F3 progeny?

50%

The average performance of many progeny is a good indication of an individual’s?

breeding value

What is the term used to describe the result of too many alleles identical by descent?

inbreeding depression

What is the term used to describe improved performance through good GCV?

hybrid vigor