EXAM 4- AGR3303 True/False

Assuming normal distribution, the mean +/- 2 standard deviations should include approximately how much of the total measurements?

95%

At a locus of two alleles A and a, the genotypic frequencies in teh Hardy-WEinberf population, after random mating, are expected to be p2, pq, q2

False

The components of phenotypic variance include only genetic variance and environmental variance

False, also have G value?

An X-linked recessive trait is never seen in females.

False, can have both copies

Affected people with an autosomal dominant trait have 100% chance to pass the trait to their kids

False, depends on if theyre AA or Aa

Heritability indicates the degree to which a characteristic is genetically determined

False, does not indicate degree, but it is a variation proportion ratio

If we know the recombination frequency of two linked genes, we can predict the outcomes of crosses with the two linked genes

False, for you to make the outcome, you need to know whether its coupling or repulsion and the recombination frequency

Odd number of crossover evens between two genes can't be detected in the test cross

False, its an even number

Some linked genes can exhibit recombination frequencies of more than 50%

False, maximum 50%, never above this

X-linked recessive traits can be passed from father to son

False, needs mother also

When heritability is high, environmental factor will not influence character

False, no matter how high environment could influence

The cellular reason for X-inactivation is to reduce the amount of nondisjunction during meiosis

False, not really related to x-inactivation

Three-point test crosses are only informative when both parents are true-breeding

False, on is heterozygote and one is homo recessive

The higher the coefficient of coincidence, the higher the crossover interference

False, opposite relationship always

One centriMorgan (cM) is one map unit and 100% recombination frequency

False, should be 1% recombination frequency

At Hardy-Weinberg equilibrium, the allele frequencies do not change from generation to generation, while genotypic frequencies can increase or decrease from generation to generation

False, the genotypic frequency will stabilize and not change

Height in all organisms is always a continuous trait

False, the height is qualitative not quantitative

Recombination of different alleles of different genes can only occur through crossing over

False, the recombination can also happen through independent assortment!!

Linked genes are allelic

False, they are not allelic

The X and Y chromosomes are named after their characteristic shape

False, they are not named after that

X and Y chromosomes can't pair and segregate into different cells in meiosis

False, they can pair 5%

Completely linked genes on the same chromosome can show independent assortment

False, they do not show independent assortment

Linked genes segregate independently

False, they don't

The condition XXXY is always lethal in humans

False, this can be a condition

Absence of Y chromosome in humans is lethal and results in embryo abortion

False, this is Turner Syndrome

Recombination frequencies can be predicted by a chi-square test

False, this is calculated by the amount of recombinants, chi square has to do with independent assortment

For the X-linked recessive traits, normally there are more females than males affected

False, this is males

As the number of loci affecting a character increases, the number of phenotypic classes in the F2 decreases

False, this is opposite

A Y-linked trait is always passed from a father to a son

True

A chromosome map shows the linear order of gene loci present on a chromosome and the relative distances between them.

True

A normal human female heterozygous for two X-linked alleles usually express only one of those alleles in any given cell in her body

True

A testcross includes one parent that is homozygous recessive for all gene loci being examined

True

A woman with normal color vision must be a carrier (heterozygote) if she has a father who is color blind

True

Autosomal recessive traits often appear to "skip" generation

True

Barr body is an inactivated X-chromosome visible in the nucleus of a cell in female mammals

True

Both autosomal recessive and dominant traits appear equally in males or females

True

Coupling and repulsion phases can result in the same phenotypes of the offspring but in very different numbers

True

Crossovers on chromosomes are frequently not independent events. The interference occurs when one crossover inhibits another

True

For the X-linked dominant trait, affected fathers normally pass the trait to daughters, but will not pass the trait to sons

True

Genotypic and allelic frequencies of samples from a population are used to represent the gene pool of the population

True

Heritability is used to estimate what proportion of a traits variance in a population is genetic variance

True

In a cross between a white-eyed female fruit fly and red-eyed male, will produce all red-eyed females and white eyed-males

True

In humans SRY is the male determining gene

True

In humans, there are about 5% pseudoautosomal regions at both tips of the X and Y chromosomes

True

Linked genes with a low recombination frequency are closer than genes with higher recombination frequency

True

Most continuously varying characteristics are both polygenic and influenced by environmental factors

True

Random mating is an important assumption in Hardy-Weinberg law

True

Standard deviation is calculated in the same units as the original measurements while variants is calculated in units squared

True

Temperature during embryonic development determines sex in reptiles like turtles and alligators.

True

The heritability of an individual cannot be estimated

True

When both parents are heterozygous for an autosomal recessive trait, 1/4 of their children will inherit the trait

True

When narrow-sense heritability is high for a particular trait, offspring tend to resemble their parents for that trait

True

Which statement is true for quantitative traits? a. Quantitative traits are normally influenced by multiple genes b. Quantitative traits are normally influenced by environmental factors. c. Quantitative traits are those for which multiple genes contribute in an equal and additive way to the phenotype. d. All of the above are true. e. a and b are true

a and b are true

Suppose that researchers estimate that broad-sense heritability of IQ in Sweden is 0.8. Which of the following conclusions is (are) valid, assuming that the estimate is accurate? a. Most variance for IQ in Sweden is due to total genetic variance. b. In Sweden, the environment does not play a role in determining the IQ of individuals. c. Enriching the environment of poor children in Sweden would not lead to improvement on IQ tests. d. Broad-sense heritability of IQ in the United States probably is close to 0.8.

a. Most variance for IQ in Sweden is due to total genetic variance.

If broad-sense heritability for a trait is very high and narrow-sense heritability is very low, which of the following must be true? a. Additive variance must be high relative to total phenotypic variance. b. Dominance variance must be high relative to total phenotypic variance. c. Environmental variance must be high relative to total phenotypic variance. d. Genotypic-environmental covariance must be high relative to total phenotypic variance.

b. Dominance variance must be high relative to total phenotypic variance

The estimated broad-sense heritability for milk production in a herd of dairy cattle is high. Which is a valid inference? a. Most of the variation in milk production in the herd is due to additive genetic variance within the herd. b. Most of the variation in milk production in the herd is due to dominant genetic variance. c. Little of the variation in milk production is due to environmental variation within the herd. d. Broad-sense heritability for milk production will be high in most other herds of dairy cattle.

c. Little of the variation in milk production is due to environmental variation within the herd.

Knowing the __________ of a trait has great practical importance because it allows statistical predictions regarding the phenotypes of offspring to be made on the basis of the parents' phenotypes. a. variance b. inbreeding coefficient c. heritability d. genotype

c. heritability

Heritability: a. is universal for a given trait. b. is the degree to which a specific trait is genetically determined. c. is specific for a given population in a specific environment. d. can be used as a quantitative measure of genetic differences between two populations.

c. is specific for a given population in a specific environment.

Suppose that pumpkin weight is controlled by five unlinked loci, each with two segregating alleles (A/a, B/b, C/c, D/d, E/e) that have additive effects. What fraction of the F2 offspring from a cross of AABBCCDDEE and aabbccddee parents are expected to have the same weight phenotype as the aabbccddee parent? a. 1/4 b. 1/10 c. (1/2)^5 d. (1/4)^5

d. (1/4)^5

______________ can cause a single genotype to produce a range of potential phenotypes. a. Epistasis b. The inbreeding coefficient c. Hybrid vigor d. Environmental effects e. Heritability

d. Environmental effects

Two highly inbred tobacco plants are crossed. One has dark green leaves. The other has yellow leaves. The F1 have light green leaves. Six hundred progeny from F1 ´ F1 crosses are analyzed. Their leaves show continuous variation in color, but none has dark green or yellow leaves. What do these data suggest about the number of genes determining this trait? a. There are 2 genes that determine this trait. b. There are 3 genes that determine this trait. c. There are 4 genes that determine this trait. d. There are more than 4 genes that determine this trait.

d. There are more than 4 genes that determine this trait.

A series of experiments shows that oil content in a diploid grain is influenced by five genes (a through e) with additive alleles. The highest producing strain is 20% oil content; the lowest has close to 0%. A plant of unknown genotype has an oil content of 12%. What is a possible genotype for this plant? (+ = additive alleles) a. a+a+b+b+c+c+d+de+e b. a+a+b+b ccddee c. a+a+b+bccddee d. aab+bc+cd+d+e+e+

d. aab+bc+cd+d+e+e+