Bio ch 14

Question 1

Pea plants were particularly well suited for use in Mendel’s breeding experiments for all of the following reasons except that

Answer 1

peas have an unusually long generation time.

Question 2

What is the difference between a monohybrid cross and a dihybrid cross?

Answer 2

A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid only one.

Question 3

A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates

Answer 3

dominance.

Question 4

The F1 offspring of Mendel’s classic pea cross always looked like one of the two parental varieties because

Answer 4

one phenotype was completely dominant over another.

Question 5

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

Answer 5

Traits are inherited in discrete units, and are not the results of “blending.”

Question 6

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

Answer 6

8

Question 7

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests

Answer 7

that the parents were both heterozygous.

Question 8

Two characters that appear in a 9:3:3:1 ratio in the F2 generation should have which of the following properties?

Answer 8

The genes controlling the characters obey the law of independent assortment.

Question 9

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?

Answer 9

HT

Question 10

It was important that Mendel examined not just the F1 generation in his breeding experiments, but the F2 generation as well, because

Answer 10

parental traits that were not observed in the F1 reappeared in the F2.

Question 11

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

Answer 11

50%

Question 12

Which of the boxes marked 1-4 correspond to plants with dark leaves?

Answer 12

1, 2, and 3

Question 13

Which of the boxes correspond to plants with a heterozygous genotype?

Answer 13

2 and 3

Question 14

Which of the plants will be true-breeding?

Answer 14

1 and 4

Question 15

Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that

Answer 15

traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.

Question 16

Which of the following about the law of segregation is false?

Answer 16

It is a method that can be used to determine the number of chromosomes in a plant.

Question 17

The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?

Answer 17

All of the genes controlling the traits behaved as if they were on different
chromosomes.

Question 18

Mendel was able to draw his ideas of segregation and independent assortment because of the influence of which of the following?

Answer 18

His experiments with the breeding of plants such as peas

Question 19

Mendel’s observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

Answer 19

Anaphase I of meiosis

Question 20

Mendel’s second law of independent assortment has its basis in which of the following events of meiosis I?

Answer 20

Alignment of tetrads at the equator

Question 21

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt  BBtt will have black fur and long tails?

Answer 21

1/2

Question 22

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?

Answer 22

0

Question 23

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 color and location assort independently. If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?

Answer 23

190

Question 24

In a cross AaBbCc  AaBbCc, what is the probability of producing the genotype AABBCC?

Answer 24

1/64

Question 25

Given the parents AABBCc  AabbCc, assume simple dominance and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?

Answer 25

3/4

Question 26

These results indicate which of the following?

Answer 26

Epistasis is involved.

Question 27

How many genes must be responsible for these coat colors in Labrador retrievers?

Answer 27

2

Question 28

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?

Answer 28

Yellow

Question 29

If true-breeding red long radishes are crossed with true breeding white oval radishes, the F1 will be expected to be which of the following?

Answer 29

Purple and long

Question 30

In the F2 generation of the above cross, which of the following phenotypic ratios would be expected?

Answer 30

6:3:3:2:1:1

Question 31

Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg). If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the following offspring would you expect?

Answer 31

All +bt +vg heterozygotes

Question 32

The flower color trait in radishes is an example of which of the following?

Answer 32

Incomplete dominance

Question 33

A 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross is a sign of

Answer 33

incomplete dominance.

Question 34

In snapdragons, heterozygotes for one of the genes have pink flowers, whereas homozygotes have red or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers?

Answer 34

100%

Question 35

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color. A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?

Answer 35

TtRr–tall and pink

Question 36

Skin color in a certain species of fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system?

Answer 36

4

Question 37

In cattle, roan coat color (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?

Answer 37

roan  roan

Question 38

The relationship between genes S and N is an example of

Answer 38

epistasis.

Question 39

A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce

Answer 39

all sharp-spined progeny.

Question 40

If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios?

Answer 40

9 sharp-spined : 3 dull-spined : 4 spineless

Question 41

A blue budgie is crossed with a white budgie. Which of the following results is not possible?

Answer 41

Green and yellow offspring

Question 42

Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies?

Answer 42

yyBb and yyBb

Question 43

Which of the following is a possible partial genotype for the son?

Answer 43

IBi

Question 44

Which of the following is a possible genotype for the mother?

Answer 44

IAi

Question 45

Which of the following is a possible phenotype for the father?

Answer 45

B positive

Question 46

Which of the following is the probable genotype for the mother?

Answer 46

IAiRr

Question 47

If both children are of blood group MM, which of the following is possible?

Answer 47

Each parent must be type M.

Question 48

Which describes the ability of a single gene to have multiple phenotypic effects

Answer 48

Pleiotropy

Question 49

Which describes the ABO blood group system?

Answer 49

Multiple alleles

Question 50

Which of the following terms best describes when the phenotype of the heterozygote differs from the phenotypes of both homozygotes?

Answer 50

Incomplete dominance

Question 51

. 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?

Answer 51

Pleiotropy

Question 52

Which of the following is an example of polygenic inheritance?

Answer 52

Skin pigmentation in humans

Question 53

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

Answer 53

Environmental factors such as soil pH

Question 54

Which of the following provides an example of epistasis?

Answer 54

In rabbits and many other mammals, one genotype (cc) prevents any fur color from developing.

Question 55

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

Answer 55

There may still be only two phenotypes for the trait.

Question 56

Huntington's disease is a dominant condition with late age of onset in humans. If one parent has the disease, what is the probability that his or her child will have the disease?

Answer 56

1/2

Question 57

A woman has six sons. The chance that her next child will be a daughter is

Answer 57

1/2.

Question 58

What is the genotype of individual II-5?

Answer 58

ww

Question 59

What is the likelihood that the progeny of IV-3 and IV-4 will have wooly hair?

Answer 59

50%

Question 60

What is the probability that individual III-1 is Ww?

Answer 60

1

Question 61

People with sickle-cell trait

Answer 61

All of the above

Question 62

When a disease is said to have a multifactorial basis, it means that

Answer 62

both genetic and environmental factors contribute to the disease.

Question 63

An ideal procedure for fetal testing in humans would have which of the following features?

Answer 63

Lowest risk procedure that would provide the most reliable information

Question 64

A scientist discovers a DNA-based test for the 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?

Answer 64

To design a test for identifying heterozygous carriers of the allele

Question 65

An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?

Answer 65

Amniocentesis

Question 66

The frequency of heterozygosity for the sickle cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?

Answer 66

Darwin's explanation of natural selection

Question 67

Cystic fibrosis (CF) is a Mendelian disorder in the human population that is inherited as a recessive. Two normal parents have two children with CF. The probability of their next child being normal for this characteristic is which of the following?

Answer 67

1/4

Question 68

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

Answer 68

Regulate the diet of the affected persons to severely limit the uptake of the amino acid.

Question 69

Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility, and death, usually of 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?

Answer 69

The disorder may be due to mutation in a single protein-coding gene.

Question 70

A pedigree analysis for a given disorder's occurrence in a family shows that, although both parents of an affected child are normal, each of the parents has had affected relatives with the same condition. The disorder is then which of the following?

Answer 70

Recessive

Question 71

One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant, although it may be either mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?

Answer 71

One of the parents has very mild expression of the gene.