Question 1

Most genes have many more than two alleles. However, which of the following is also true?

Accepted Answer

A) At least one allele for a gene always produces a dominant phenotype. 
B) Most of the alleles will never be found in a live-born organism. 
C) All of the alleles but one will produce harmful effects if homozygous. 
D) There may still be only two phenotypes for the trait. 
E) More than two alleles in a genotype is considered lethal.

Question 2

Phenylketonuria (PKU)is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. The amino acid is not otherwise produced by humans. Therefore, the most efficient and effective treatment is which of the following?

Accepted Answer

A) Feed them the substrate that can be metabolized into this amino acid. 
B) Transfuse the patients with blood from unaffected donors. 
C) Regulate the diet of the affected persons to severely limit the uptake of the amino acid. 
D) Feed the patients the missing enzymes in a regular cycle, such as twice per week. 
E) Feed the patients an excess of the missing product.

Question 3

Use the following information to answer the questions below.
Tay-Sachs disease is an inherited genetic disorder in which the gene sequence codes for an enzyme involved in lipid metabolism. Accumulation of lipids in the brain leads to seizures, blindness, loss of neural function, and early death. People can be carriers of this disease and only homozygotic offspring will die from this disorder.
-How can you reconcile these conclusions?

Accepted Answer

A) These alleles are really displaying incomplete dominance. 
B) There is a polygenic effect, where another gene encodes for the same enzyme. 
C) This is a result of epistasis. 
D) The observed dominant/recessive relationship of alleles depends on the level at which the phenotype is examined. 
E) The observed dominant/recessive relationship of alleles only applies at the organismal level.

Question 4

Use the following description and figure to answer the questions below.
In a particular plant, leaf colour is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.
 
-Which of the boxes correspond to plants with a heterozygous genotype?

Accepted Answer

A) 1 
B) 1 and 2 
C) 1, 2, and 3 
D) 2 and 3 
E) 2, 3, and 4

Question 5

Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility and death, usually from coronary artery disease, at an average age of approximately 13. Patients, who look very old even as children, do not live to reproduce. Which of the following represents the most likely assumption?

Accepted Answer

A) All cases must occur in relatives; therefore, there must be only one mutant allele. 
B) Successive generations of a family will continue to have more and more cases over time. 
C) The disorder may be due to mutation in a single protein-coding gene. 
D) Each patient will have had at least one affected family member in a previous generation. 
E) The disease is autosomal dominant.

Question 6

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Accepted Answer

A) There is considerable genetic variation in garden peas. 
B) Traits are inherited in discrete units, and are not the results of "blending." 
C) Recessive genes occur more frequently in the F₁ generation than do dominant ones. 
D) Genes are composed of DNA. 
E) An organism that is homozygous for many recessive traits is at a disadvantage.

Question 7

Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes ocular problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information?

Accepted Answer

A) It is recessive. 
B) It is dominant. 
C) It has a late age of onset (> 60). 
D) It is pleiotropic. 
E) It is epistatic.

Question 8

Which of the following is the best statement of the use of the addition rule of probability?

Accepted Answer

A) the probability that two or more independent events will both occur 
B) the probability that two or more independent events will both occur in the offspring of one set of parents 
C) the probability that either one of two independent events will occur 
D) the probability of producing two or more heterozygous offspring 
E) the likelihood that a trait is due to two or more meiotic events

Question 9

Refer to the following information to answer the questions below.
Gene S controls the sharpness of spines in a type of cactus. Cacti with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cacti have dull spines. At the same time, a second gene, N, determines whether or not cacti have spines. Homozygous recessive nn cacti have no spines at all.
-A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce

Accepted Answer

A) all sharp-spined progeny. 
B) 50% sharp-spined, 50% dull-spined progeny. 
C) 25% sharp-spined, 50% dull-spined, 25% spineless progeny. 
D) all spineless progeny. 
E) It is impossible to determine the phenotypes of the progeny.

Question 10

A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Of the following, which is the best use of this discovery?

Accepted Answer

A) Screen all newborns of an at-risk population. 
B) Design a test for identifying heterozygous carriers of the allele. 
C) Introduce a normal allele into deficient newborns. 
D) Follow the segregation of the allele during meiosis. 
E) Test school-age children for the disorder.

Question 11

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
-In one type cross of black × black, the results were as follows: 9/16 black
4/16 yellow
3/16 brown
The genotype aabb must result in which of the following?

Accepted Answer

A) black 
B) brown 
C) yellow 
D) a lethal result 
E) white

Question 12

A sexually reproducing animal has two unlinked genes, one for head shape (H)and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

Accepted Answer

A) tt 
B) Hh 
C) HhTt 
D) T 
E) HT

Question 13

Use the following information to answer the questions below.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
-How many genes must be responsible for these coat colours in Labrador retrievers?

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
E) 5

Question 14

(The)________: when two alleles separate from each other and end up in separate gametes.

Accepted Answer

A) law of independent assortment 
B) law of segregation 
C) chiasmata 
D) Epistasis 
E) Aneuploidy

Question 15

________ is when a gene on one locus has an influence on the phenotypic expression of an allele at another locus.

Accepted Answer

A) Polygenic influence 
B) Pleiotropy 
C) Multifactorial occurrence 
D) Epistasis 
E) Segregation

Question 16

In cattle, roan coat colour (mixed red and white hairs)occurs in the heterozygous (Rr)offspring of red (RR)and white (rr)homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

Accepted Answer

A) red × white 
B) roan × roan 
C) white × roan 
D) red × roan 
E) The answer cannot be determined from the information provided.

Question 17

Use the following information to answer the questions below.
Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F₁ individuals have red, axial flowers. The genes for flower colour and location assort independently.
-If 1000 F₂ offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?

Accepted Answer

A) 65 
B) 190 
C) 250 
D) 565 
E) 750

Question 18

Refer to the following information to answer the questions below.
Humanoids on the newly explored planet Brin (in a hypothetical galaxy in ~50 years from the present) have a gene structure similar to our own, but many very different plants and animals.
-One species of green plant, with frondlike leaves, a spine-coated stem, and purple cup-shaped flowers, is found to be self-pollinating. Which of the following is true of this species?

Accepted Answer

A) The species must be haploid. 
B) Its reproduction is asexual. 
C) All members of the species have the same genotype. 
D) Some of the seeds would have true-breeding traits. 
E) All of its dominant traits are most frequent.

Question 19

Use the following information to answer the questions below.
Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg).
-If flies that are heterozygous for both the bent wing gene and the vestigial wing gene are mated, what is the probability of offspring with bent wings only?

Accepted Answer

A) 1/8 
B) 3/8 
C) 1/4 
D) 9/16 
E) 3/16

Question 20

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?

Accepted Answer

A) incomplete dominance 
B) multiple alleles 
C) pleiotropy 
D) epistasis 
E) codominance

Exam 14: Mendel and the Gene Idea

Most genes have many more than two alleles. However, which of the following is also true?

Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. The amino acid is not otherwise produced by humans. Therefore, the most efficient and effective treatment is which of the following?

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Which of the following is the best statement of the use of the addition rule of probability?

A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Of the following, which is the best use of this discovery?

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T) . Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

(The) ________: when two alleles separate from each other and end up in separate gametes.

________ is when a gene on one locus has an influence on the phenotypic expression of an allele at another locus.

In cattle, roan coat colour (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?