Genetics Exam I

Front 1

A trait exhibits incomplete dominance. If one of the two alleles is a loss-of-function allele, a reasonable molecular explanation would be

a. 50% of the functional protein is not enough to give the same phenotype as 100%.
b. The functional allele is up-regulated in the heterozygote.
c. The nonfunctional allele is up-regulated in the heterozygote.
d. 50% of the functional protein gives the same phenotype as 100%.

Back 1

a. 50% of the functional protein is not enough to give the same phenotype as 100%

Front 2

wo different strains of plant exhibit a recessive phenotype of white flowers. When crossed, they produce offspring with wild-type purple flowers. This phenomenon is called __________ and it indicates that _________________________________.Select one:

a. epistasis/the recessive alleles mask the dominant alleles.

b. complementation/the recessive alleles are in two different genes.

c. epistasis/the recessive alleles are in two different genes.

d. complementation/the recessive alleles mask the dominant alleles.

Back 2

b. complementation/the recessive alleles are in two different genes.

Front 3

Hemophilia, type A, is an X-linked recessive trait. A mother without hemophilia and a father with hemophilia have a daughter with hemophilia. If their next offspring is a son, which is the likelihood that this son will have hemophilia?Select one:

a. 100%

b. 25%

c. 50%

d. 0%

Back 3

c. 50%

Front 4

The length of the index finger is sex-influenced. The short allele is dominant in males, whereas the long allele is dominant in females. If a heterozygous male and a female with short index fingers have offspring together, what are the possible phenotypes of the offspring?Select one:

a. males with long index fingers and females with long index fingers
b. males with short or long index fingers and females with short index fingers
c. males with short index fingers and females with long index fingers
d. males with short index fingers and females with short or long index fingers

Back 4

d. males with short index fingers and females with short or long index fingers

Front 5

In humans, an individual who is XXY would be aSelect one:

a. male
b. female
c. hermaphrodite
d. none of the above

Back 5

a. Male

Front 6

An explanation for overdominance isSelect one:

a. the inability of a pathogen to propagate in cells.
b. homodimer formation.
c. variation in functional activity.
d. all of the above.

Back 6

d. All of the above.

Front 7

A heterozygous plant, GgHhIiJjKk is allowed to self fertilize. What is the probability that an offspring will be GGHhIiJjkk?Select one:

a. 1/4 = 0.75

b. 1/128 = 0.0078

c. 1/1024 = 0.00098

d. 243/1024 = 0.24

Back 7

b. 1/128 = 0.00098

Front 8

Which of the following statements is false?Select one:

a. An allele is a gene.
b. A heterozygote has different alleles for a given gene.
c. For most species, a chromosome carries a single gene.
d. A true-breeding individual is homozygous.

Back 8

c. For most species, a chromosome carries a single gene.

Front 9

Which of the following patterns is/are consistent with this pedigree?Select one:

a. X-linked recessive only
b. Autosomal dominant only
c. Autosomal dominant and autosomal recessive
d. Autosomal recessive only

Back 9

b. Autosomal dominant only

Front 10

A female who is IA i has offspring with a father who IB IB. Which blood type(s) would not be possible for their offspring? Select one:

a. Type A

b. Type O

c. Type A and type O

d. Type AB and type O

Back 10

c. Type A and type O

Front 11

Which of the following statements regarding the imprinting of genes (such as Igf2, PWS gene, or AS gene) is generally correct? Select one:

a. Imprinting involves methylation that first occurs during spermatogenesis.
b. Imprinting involves methylation that first occurs during oogenesis.
c. Imprinting involves methylation that first occurs during spermatogenesis or oogenesis, but not both.
d. Imprinting involves methylation that first occurs during embryogenesis.

Back 11

c. Imprinting involves methylation that first occurs during spermatogenesis or oogenesis

Front 12

What is the molecular/cellular explanation for maternal effect? Select one:

a. The father’s gene is silenced at fertilization. b. During oogenesis, nurse cells transfer gene products to the oocyte.
c. The gene products from nurse cells are needed during the very early stages of development.
d. Both b and c are correct

Back 12

d. Both b and c are correct

Front 13

In mice, the copy of the Igf2 gene that is inherited from the mother is never expressed in her offspring. This happens because the Igf2 gene from the mother Select one:

a. is deleted during embryonic development. b. always undergoes a mutation that inactivates its function.
c. is deleted during oogenesis.
d. is not transcribed in the somatic cells of the offspring.

Back 13

d. is not transcribed in the somatic cells of the offspring

Front 14

In most species, the transmission of mitochondria follows Select one:

a. a maternal inheritance pattern.
b. a paternal inheritance pattern.
c. a biparental inheritance pattern.
d. none of the above.

Back 14

a. A maternal inheritance pattern

Front 15

In mice, a true-breeding female with a normal spine is crossed to a true-breeding male with a crooked spine. All of the F1 offspring have normal spines. The F1 female offspring are then crossed to true-breeding males with a crooked spine. All of the F2 offspring have normal spines. These are observations are consistent with Select one:

a. maternal effect.
b. genomic imprinting.
c. maternal inheritance.
d. both a and c.

Back 15

d. both a and c

Front 16

The purpose of X inactivation is
Select one:

a. dosage compensation.
b. sex determination.
c. to eliminate the X chromosome from cells.
d. to eliminate the Y chromosome from cells

Back 16

a. dosage compensation

Front 17

The Igf2 gene that is inherited from the mother is silenced due to imprinting. A mutation, which we will call Igf2¯, is a loss-of-function mutation. If an Igf2¯Igf2¯ mother is crossed to an Igf2Igf2¯ father, what is the predicted outcome? Select one:

a. All offspring would be normal.
b. All offspring would be dwarf.
c. Half of the offspring would be normal, and half would be dwarf.
d. Could be b or c.

Back 17

c. Half of the offspring would be normal, and half would be dwarf.

Front 18

In snails, coiling is controlled by a maternal effect gene in which D (right) is dominant to d (left). A female that coils to the left has offspring that coil to the right. What are the genotypes of the mother of these offspring and the maternal grandmother, respectively? Select one:
a. Dd, dd
b. dd, Dd
c. Dd, Dd
d. dd, DD

Back 18

a. Dd, dd

Front 19

A cross is made between a green four-o’clock and a variegated four o’clock. Green chlorophyll synthesis is inherited via the chloroplasts, which are maternally inherited in this species. If the variegated plant provides the pollen, the expected outcome of the offspring would be Select one:

a. 3 plants with green leaves to 1 plant with variegated leaves.

b. 3 plants with green leaves to 1 plant with white leaves.

c. some plants with green leaves, some with variegated leaves, and some with white leaves. d. all plants with green leaves.

Back 19

a. 3 plants with green leaves to 1 plant with variegated leaves

Front 20

Due to imprinting, males silence the AS gene. A female born with Angelman syndrome carries a deletion in the AS gene (i.e., the UBE3A gene). Which parent transmitted the deletion to her? Select one:

a. her mother

b. either her mother or father

c. not enough information is provided to answer this question

d. her father

Back 20

d. Her father

Front 21

Which of the following statements correctly describes how the linkage pattern involving two genes can be altered and transmitted to offspring? Select one:

a. During mitosis, a crossover initiates between homologues in the region between the two genes.

b. During mitosis, a crossover initiates between sister chromatids in the region between the two genes.

c. During meiosis, a crossover initiates between sister chromatids in the region between the two genes.

d. During meiosis, a crossover initiates between homologues in the region between the two genes.

Back 21

d. During meiosis, a crossover initiates between homologues in the region between the two genes

Front 22

By conducting testcrosses, researchers have found that the apple has 17 linkage groups. How many chromosomes would you expect to find in leaf cells? Select one:

a. 2

b. 17

c. 34

d. None of the above

Back 22

c. 34

Front 23

Morgan observed a higher number of recombinant offspring involving eye color and wing length (401 + 318) compared to body color and eye color (17 + 12). These results occurred because Select one:

a. the gene affecting wing length is not on the X chromosome.
b. the genes affecting eye color and wing length are farther apart on the X chromosome compared to the genes affecting body color and eye color.
c. the gene affecting body color is not on the X chromosome.
d. the genes affecting eye color and wing length are closer together on the X chromosome compared to the genes affecting body color and eye color.

Back 23

b. the genes affecting eye color and wing length are farther apart on the X chromosome compared to the genes affecting body color and eye color

Front 24

In genetics, the term “linkage” means that Select one:

a. two or more genes are on the same chromosome.
b. two or more genes tend to be transmitted as a unit.
c. two or more genes have the same function. d. both a and b are correct.

Back 24

d. both a and b are correct

Front 25

Two genes are 18 map units apart. In a testcross, what percentage of offspring is expected to be recombinants?

a. 9

b. 18

c. 25

d. 36

Back 25

b. 18

Front 26

With regard to linked genes along the same chromosome, which of the following statements is false?

a. Crossing over that separates linked alleles occurs during prophase of meiosis I.

b. Crossing over is more likely to separate alleles if they are far apart on the same chromosome.

c. Crossing over is needed to produce recombinant offspring.

d. Crossing over is needed to produce parental offspring.

Back 26

d. crossing over is needed to produce parental offspring

Front 27

A researcher conducted crosses between two different strains of Drosophila. When true-breeding flies with singed bristles (s) and normal wings (L) were crossed to true-breeding flies with normal bristles (S) and vestigial wings (l), all F1 offspring had normal wings and normal bristles. The F1 offspring were crossed to flies with singed bristles and vestigial wings. Which F2 offspring is/are recombinant?Select one:

a. Singed bristles/vestigial wings and normal bristles/normal wings
b. Singed bristles/normal wings only
c. Singed bristles/vestigial wings only
d. Singed bristles/normal wings and normal bristles/vestigial wings

Back 27

a. singed bristles/vestigial wings and normal bristles/normal wings

Front 28

The phenomenon of linkage defies

a. Mendel's law of segregation

b. Mendel/s law of independent assortment

c. both a and b.

d. neither a nor b.

Back 28

b. Mendel/s law of independent assortment

Front 29

Two genes are 22 map units apart on the same chromosome. A true-breeding GGhh individual is crossed to a true-breeding ggHH individual. The F1 offspring are mated to gghh individuals. If this testcross produces 1000 offspring, how many of them would you expect to be GgHh?

a. 390

b. 220

c. 110

d. 250

Back 29

c. 110

Front 30

In a chi square analysis involving genes that may be linked, which of the following statements is correct? Select one:

a. A large chi square value suggests that the observed and expected data are in good agreement.

b. The hypothesis is rejected when the chi square value is very low.

c. An independent assortment hypothesis is not proposed because the data usually suggest linkage.

d. An independent assortment hypothesis is proposed because it allows you to calculate expected numbers of offspring.

Back 30

d. An independent assortment hypothesis is proposed because it allows you to calculate expected numbers of offspring

Front 31

Law of Independent Assortment

Back 31

Two different genes will randomly assort their alleles during the formation of haploid cells.

Phenotype 9:3:3:1 with homozygous crosses

Front 32

Explain why Bb and BB have the same phenotype (the b is due to a recessive loss of function mutation)

Back 32

The recessive allele doesn't affect the phenotype of the heterozygote. A single copy of the dominant allele is enough to cover the effects of the recessive allele.

Front 33

Up-regulation

Back 33

When the heterozygote actually produces more than 50% of the functional protein therefore the dominant phenotype is expressed (compensates for the lack of function of the defective allele

Front 34

homodimer

Back 34

protein composed of two subunits that are encoded by the same gene

Front 35

When does crossing over occur

Back 35

meiosis I in the pachytene stage

Front 36

Spermatogenesis

Back 36

produces 4 haploid sperm cells

Front 37

Oogenesis

Back 37

produces a single haploid cell

Front 38

Haploinsufficiency

Back 38

heterozygote exhibits an abnormal or disease phenotype

Front 39

Dominant-negative mutation

Back 39

protein encoded by the mutant gene acts antagonistically. Mutant protein counteracts the effects of the normal protein, altering the phenotype

Front 40

Gain of function mutation

Back 40

mutant gene is over expressed or expressed in the wrong cell type

Front 41

Epistasis

Back 41

alleles of one gene mask the phenotypic effects of the alleles of another gene

Front 42

Complementation

Back 42

the production of offspring with a wild type phenotype from parents that both display the same or similar recessive phenomenon

Front 43

Info do you need to predict the phenotypic outcome of DWARFISM due to a mutant lgf 2 allele

Back 43

genotype of the father (genomic imprinting)

Front 44

Snail coiling direction

Back 44

genotype of mother (maternal effect)

Front 45

Leber hereditary optic neuropathy

Back 45

mtDNA genotype of the other (extranuclear inheritance)

Front 46

Genetic Linkage

Back 46

genes are close together on the same chromosome tend to be transmitted as a unit - genetic linkage has an influence on inheritance patterns