Deck 19: Developmental Genetics

Question 1

A pure- breeding tree that produces fruit with 12 seeds, the smallest number of seeds possible, is mated with a pure- breeding tree that produces fruit with 36 seeds, the largest number of seeds possible. This polygenic trait is controlled by two alleles, which both contribute to the phenotype, present at multiple loci. When two F1 individuals are mated, 7 phenotypes result. Which of the following statements is FALSE?

A) One of the additive alleles contributes 2 seeds to the seed content of the fruit.
B) There are 3 genes that control this polygenic trait.
C) One of the additive alleles contributes 6 seeds to the seed content of the fruit.
D) One of the F2 phenotypic classes has 18 seeds.
E) The F1 offspring all have 24 seeds.

Answer 1

D

Question 2

A scientist is studying insect wing length. An individual from a pure- breeding parental line (P1), for which the VP is 40 mm2, is mated with an individual from a pure- breeding parental line (P2), for which the VP is 80 mm2. This results in F1 progeny that have a VP of 54 mm2. A cross between two F1 progeny results in offspring with a VP of 92 mm. What is the genotypic variance?

A) 34 mm
B) 32 mm
C) 14 mm
D) 38 mm
E) 58 mm

Answer 2

A

Question 3

Which of the following formulas can be used to calculate broad sense heritability (H2)?

A) VA / VP
B) (VA + VD + VI)/ VP
C) VE / VP
D) R/S
E) S(h2)

Answer 3

B

Question 4

As broad sense heritability (H2) approaches 0.0, which of the following must be true?

A) Almost all the variation in phenotype is VE.
B) Identical (MZ) twins are virtually all discordant.
C) Almost all the variation in phenotype is VG.
D) Narrow sense heritability (h2) approaches 1.
E) Fraternal (DZ) twins are virtually all concordant.

Question 5

A scientist is researching oil content of seeds from a new plant species named R. tificial. She has determined the narrow sense heritability (h2) is 0.80. She mates plants with an average seed oil content of 32%. If the response to selection (R) was 16%, what is the estimated average oil content of seeds in the entire lab population?

A) 32%
B) 50%
C) 20%
D) 12%
E) 44%

Question 6

Which of the following is FALSE regarding human multifactorial traits?

A) They usually exhibit discontinuous variation.
B) They are influenced by genetic and environmental factors.
C) They are influenced by multiple genes.
D) They are usually quantitative rather than qualitative.
E) Their phenotype can be maximized by environmental factors to reach a genetic potential.

Question 7

A scientist is researching oil content of seeds from a new plant species named R. tificial. The average oil content from plants in her lab population is 52%, and she has determined the narrow sense heritability (h2) is 0.60. If she randomly mates individuals with 70%, 71%, 72%, 73%, and 74% seed oil content what is the expected response to selection (R)?

A) 31.2%
B) 12%
C) 6%
D) 72%
E) 24%

Question 8

An animal breeder asks your advice about which, of a number of traits, could most effectively be selected for in his herd. A trait with which of the following would you most correctly suggest?

A) a high VP relative to VG
B) a high VE
C) a low h2 value
D) a high VA relative to VP
E) a low response to selection (R)

Question 9

A group is experimenting with selection in an insect species due to exposure to a newly developed insecticide, cpd AW143. The group has found that after 10 generations of exposure, the population is now bimodal in its response to the drug. Close to 30% of the population are completely normal while 70% live only about 1/6 of the normal lifetime. This is an example of .

A) threshold effect
B) stabilizing selection
C) disruptive selection
D) directional selection
E) additive genes

Question 10

For the following traits, the concordances of MZ and DZ twins are given as percentages. Which trait unlikely to have a strong genetic influence?

Question 11

A group is experimenting with selection in a mouse model for a disease that is lethal in mid- life. After 30 generations of exposure, the population's average life span is near that of a wild- type mouse population. What type of selection did the model mouse population undergo?

A) disruptive selection
B) directional selection
C) threshold effect
D) additive genes
E) stabilizing selection

Question 12

For a specific trait, monozygotic twins have a phenotypic variance of 15% and dizygotic twins have a phenotypic variance of 40%. Which of the following can be concluded for this trait based on this data from a twin study?

A) VG for monozygotic twins is 15%
B) VG for dizygotic twins is 25%
C) VE for monozygotic twins is 30%
D) VG for dizygotic twins is 50%
E) VE for dizygotic twins is 25%

Question 13

A sexually reproducing species of algae has been engineered to produce biofuels with varying yields. A colony with the highest yield is stimulated to reproduce with a colony with the lowest yield and the resulting F1 progeny are allowed to grow. Yields among the F1 generation have a variance of 7.8 g2. The F1 are allowed to mate and the resulting progeny are sampled and found to have a variance of 9.1 g2. Assuming that the F1 progeny are genetically uniform, determine the broad sense heritability (H2) and interpret if genetic heritability is low or high.

A) H2 = 0.86, genetic variability is high
B) H2 = 0.17, genetic variability is low
C) H2 = 0.14, genetic variability is high
D) H2 = 0.14, genetic variability is low
E) H2 = 0.86, genetic variability is low

Question 14

A hypothetical condition in some domesticated fowl is identified phenotypically by patchy loss of feathers on the animals' backs. Although several factors, genetic and environmental, are found to be involved, only about 3% of any population with any of these factors are found with feather loss. Which of the following is a likely cause?

A) continuous variation
B) high number of alleles in one of the genes
C) low mutation frequency
D) threshold of liability
E) high number of environmental effects

Question 15

How many distinct phenotypic categories should be observed for a polygenic trait in humans that results from segregation of additive alleles for 10 genes?

A) 5
B) 20
C) 21
D) 10
E) 4

Question 16

QTL mapping resembles linkage analysis primarily because .

A) it uses the three- point mapping method
B) it uses statistics to analyze its data
C) the results are quantifiable
D) it uses the location of a known DNA marker
E) the distances are reported in cM

Question 17

Which of these statements about heritability is FALSE?

A) Twin studies can offer insight into broad sense heritability of human traits.
B) Broad sense heritability measures the ratio of genetic variance to phenotypic variance.
C) Heritability measures the extent to which environmental variation contributes to the total phenotypic variation.
D) High narrow sense heritability values are correlated with a greater degree of response to artificial selection.
E) Narrow sense heritability measures the contribution of additive genotypic variance to phenotypic variance.

Question 18

A cultivator is breeding a crop for increased fruit production. The mean fruit weight in the population in 500g and the plants selected for breeding have an average fruit weight of 450g. The response to selection (R) is - 25g. What is the narrow sense heritability (h2)?

A) h2 = 0.20
B) h2 = 2.00
C) h2 = 0.05
D) h2 = 0.50
E) h2 = 0.06

Question 19

It is clearly established that obesity has greatly increased in children over the last several decades in the United States. While several genes have been identified that increase the potential for obesity, environmental influences are also involved. Which of the following is most likely?

A) There is little or no gene- environment interaction.
B) There is a demonstrable threshold of environmental effects.
C) There is a wide range of phenotypes with each genotype.
D) There is a small overlap of phenotypic ranges of different genotypes.
E) Phenotypic variation is discontinuous.

Question 20

The brain mass in a population of mice has a phenotypic variance of 0.56 g2 and an environmental variance of 0.14 g2. What is the broad sense heritability (H2)?

A) 1.54
B) 0.25
C) 0.75
D) 0.42
E) The broad sense heritability cannot be calculated with the data provided

Question 21

While most additive polygenic traits show continuous distribution, some can be divided into two or more categories based on their contribution to genetic liability. Such traits are said to have what separation between affected and unaffected members of a population?

Question 22

A strain of a cereal grain can be either dark tan, medium- dark tan, medium tan, light tan, or cream colored. When a dark tan and a cream plant are crossed, all F1 are medium tan. The F2 are distributed in a ratio of 1:4:6:4:1 from darkest to lightest. How many genes are involved in this coloration?

Question 23

What is the mean, variance (s2), and standard deviation (s) of the following sample: 1.00, 2.00, 3.00, 5.00, 7.00, 9.00, 10.00, and 11.00.

Question 24

A strain of a cereal grain can be either dark tan, medium- dark tan, medium tan, light tan, or cream colored. When plants pure- breeding for dark tan grains and cream grains are crossed, all F1 have medium tan grains. If the F1 are crossed, what proportion of the F2 will be light tan?

Question 25

If H2 for club foot is estimated as 80%, would you expect a small difference in concordances between MZ and DZ twins, such as 30 versus 27, or a large difference, such as 30 versus 2?

Question 26

If the odds ratio for a particular QTL/DNA marker pair is 2.2, this indicates that the organism is how many times more likely to get Q10M10 gametes?

Question 27

Calculate the narrow sense heritability (h2) for the following data on a trait in turkeys:
VA = 11.0
VE = 94.4
VP = 114.2
VD = 13.8

Question 28

Parkinson disease (PD) is a neurodegenerative disease that has been associated with a significant number of different genes, therefore showing it to be genetically heterogenic. One recent study in 278 families found evidence of two such possible loci. Evidence for linkage to chromosome 18q11 was presented by Gao et al. in 2009. Which of the following would be considered reputable evidence for this?

A) finding the locus to be in Hardy- Weinberg equilibrium in the population
B) finding the lod score for association between the chromosomal location and PD to be 4.1
C) use of persons from multiple ethnic and geographic backgrounds in the study
D) analysis of all other possible SNPs with no such association to chromosome 18
E) lack of quantitative difference for the occurrence of both loci in individuals

Question 29

Genetic variance can be partitioned into which three types of variance?

Question 30

Mean platelet volume (MPV) in humans increases with heart attacks and strokes and is used to predict recurrence as well as mortality. MPV has high heritability. A recent GWA study found MPV to be associated with SNPs on chromosomes 12, 3, and 17, respectively. These three QTLs accounted for 4- 5% of MPV variance. Which of the following is a reasonable explanation?

A) Other loci may also account for significant variance of MPV.
B) The three SNPs, when sequenced, should show high conservation.
C) Monitoring of these SNPs should identify those at highest risk.
D) These SNPs must be translocated or transposed alleles.
E) The three SNPs will be found in genes responsible for stroke.

Question 31

Which of the following is true?

A) GWAS is able to determine a single gene that plays the sole role in the development of Crohn's disease.
B) GWAS requires controlled crosses and the formation of introgression lines.
C) QTL mapping approaches can analyze organisms in random mating populations.
D) GWAS can scan the entire genome for QTLs by statistically testing for marker variants.
E) QTL mapping can directly identify the gene responsible for the associated phenotypic variation.

Question 32

Which component of variance in a trait such as stamina in horses is the best indicator of whether the trait will respond to selection?

Question 33

Although no specific gene alteration has yet been demonstrated as a cause for schizophrenia (SZ), it is known to have a strong genetic component. A recent study has found a strong association between SZ and a locus at chromosome 10q22- 23 in Ashkenazi Jewish and Taiwanese Han populations. Which of the following is probable?

A) The neuregulin- 3 gene at this locus is mutated in all or most SZ cases.
B) Other populations will have the same association with 10q22- 23.
C) SZ exhibits significant genetic heterogeneity in different populations.
D) People with SZ being characterized differently in various medical communities results in this association between the Jewish and Han populations.
E) The region on 10q must include several genes associated with SZ.

Question 34

Which will exhibit the most shared maternal effects (uterine environment, etc.), identical or fraternal twins?

Question 35

In which order should the following steps be done to identify a quantitative trait locus (QTL) gene t contributes to the phenotypic variation in a trait? I. DNA and protein sequence analyses are used to determine if there is a correlation with phenoty variation
II) Each of the offspring is individually backcrossed with the same parent, usually the one expressi phenotype more strongly
III) Lod scores are calculated for each genetic marker to find QTLs
IV) The genotype of the progeny at genetic markers located every 5- 10 cM is determined for each introgression line
V) Two individuals which exhibit the extremes of a specific phenotype are crossed
VI) DNA sequence variants among introgression lines are analyzed to find candidate genes

A) V, II, IV, III, VI, I
B) V, IV, III, II, VI, I
C) V, IV, II, III, I, VI
D) I, V, III, II, IV, VI
E) I, II, IV, III, VI, V

Question 36

Of mean, median, and modal, what value is the most common value in a given population?

Question 37

What is the statistically acceptable lod score that provides evidence of genetic linkage?

Question 38

Once a chromosomal position for a putative gene associated with Parkinson disease is verified, which of the following is a next step?

A) ascertaining all living and at- risk individuals who are family members of the affected test subjects
B) fine mapping of the linkage region to identify particular variants for influencing risk
C) developing a FISH screening test to identify pre- Parkinson patients
D) determining whether this locus is mutated in all Parkinson patients
E) using a genome- wide linkage SNP panel to identify more minor genes

Question 39

What two measures describe the distribution of a trait in a sample?

Question 40

QTLs are most often mapped relative to DNA markers by using what scores as measurement?

Question 41

In a newly discovered diploid animal species, tail length is determined solely by 3 additive gene loci that can have the allele s, which contributes 4mm, and the allele l, which contributes 15mm. Two lines with the genotypes AsAsBsBsClCl and AlAlBsBsCsCs are mated to create the F1 generation.
a. What is the predicted genotype and phenotype of the F1 progeny?
b. If two individuals from the F1 generation are crossed, each phenotypic category will occur in what proportion?

Question 42

Many human behavioral traits have both genetic and environmental components. Bipolar disorder has long been known to be familial, and more recently a number of genes and/or SNPs have been found to be involved. What are three or more reasons that this research has been hampered?

Question 43

In a newly discovered diploid animal species, tail length is determined solely by 2 additive gene loci that can have the allele s, which contributes 4mm, and the allele l, which contributes 15mm. Two lines with the genotypes AsAsBsBs and AlAlBsBs are mated to create the F1 generation.
a. What is the predicted genotype and phenotype of the F1 progeny?
b. If two individuals from the F1 generation are crossed, each phenotypic category will occur in what proportion?

Question 44

Distinguish between broad sense heritability and narrow sense heritability, and explain how either or both of these measures can be used to inform those using artificial selection.

Question 45

The part of the genetic variance that is attributed to epistatic interactions is called the
variance.

Question 46

A GWA study relies on the correlation between a QTL and a .

Question 47

Recent work in Drosophila demonstrated that the genes known as the chromatin remodeling complex
co- localize at loci for hsp genes that respond to heat shock. Outline a procedure you could use to substantiate this finding.

Question 48

Given a list of concordances (as percentages) for monozygotic and dizygotic twins for a selection of traits, describe how you would evaluate the relative input of environmental versus genetic factors for each trait.

Question 49

In some traits, different phenotypes result from genes whose alleles each contribute a specific increment to the whole. The phenotypes then have a phenotypic distribution.

Question 50

Describe how quantitative traits can be explained in Mendelian terms.

Question 51

After successful QTL mapping, _ lines, which result from the repeatedly backcrossing to form highly inbred lines, can help identify QTL genes.

Question 52

After locating a genome region likely to include a QTL, what must be found in this region?

Question 53

If a trait results from genetic variation as well as environmental factors, it is known as a
trait.