Chapter 23

Question 1

Alternative forms of a gene that influence the same trait and are found at the same location in homologous chromosomes are called

Answer 1

alleles

Question 2

physical characteristics of the individual

Answer 2

phenotypes

Question 3

What are alleles?

Answer 3

alternative forms of a gene for a single trait, such as blue eyes or brown eyes

Question 4

The _____ indicates the gene combination of an individual.

Answer 4

genotype

Question 5

the law of independent assortment

Answer 5

It is based upon the process of meiosis, Each pair of factors separates independently, All possible combinations of factors can occur in the gametes

Question 6

according to Mendel’s law of segregation…

Answer 6

Each individual contains two alleles for each trait, Alleles separate from each other during gamete formation, Each gamete contains one copy of each allele, Fertilization restores the presence of two alleles

Question 7

Mendel’s law of segregation implies that the two members of an allele pair

Answer 7

are distributed to separate gametes

Question 8

In a Mendelian monohybrid cross involving two homozygous genotypes, the ____ generation is always completely heterozygous.

Answer 8

F1

Question 9

What will the genotypic ratio be of a monohybrid cross of two individuals who are both heterozygous for a trait?

Answer 9

25% homozygous dominant, 50% heterozygous, 25% homozygous recessive

Question 10

A pheasant breeder starts with two birds in the P generation, one of which is AA and the other is aa. If he takes two of the birds from the F1 generation and breeds them together, what can he expect in his F2 offspring?

Answer 10

AA, Aa, and aa

Question 11

A woman who can roll her tongue (presumably dominant) is married to a man who cannot. Two of their four children can roll their tongues and two cannot. If A = roll tongue and a = cannot roll tongue, then what is the genotype of the parents?

Answer 11

woman Aa; man aa

Question 12

Some plants fail to produce chlorophyll, due to a recessive trait. If we locate a pea plant that is heterozygous for this trait, self-pollinate it, and harvest the seeds, what are the likely phenotypes of the resulting offspring?

Answer 12

About one-fourth will be white and three-fourths green since it is similar to a monohybrid cross.

Question 13

A cross is made between two parents with genotypes AaBB and aabb. If there are 32 offspring, how many of them would be expected to exhibit both dominant characteristics?

Answer 13

16

Question 14

In guinea pigs, B = black, b = brown, S = short hair, s = long hair. A heterozygous black, short-haired animal reproduces with a brown, long-haired animal. What is the expected phenotypic ratio of the offspring?

Answer 14

1 black short hair, 1 black long hair, 1 brown short hair, 1 brown long hair

Question 15

In humans, aniridia, a type of blindness, is due to a dominant allele A. Migraine headaches are due to another dominant allele M. If a man who suffers from both conditions (AaMm) marries a woman who suffers from both (AaMm), what are the chances of an offspring expressing both traits.

Answer 15

9/16

Question 16

In which kind of cross could you expect to find ratios of 1:1:1:1 among the offspring?

Answer 16

two-trait test cross

Question 17

In guinea pigs, B = black, b = brown, S = short hair, s = long hair. Two heterozygous individuals reproduce. The expected results are

Answer 17

9 black short hair, 3 black long hair, 3 brown short hair, 1 brown long hair.

Question 18

What genetic disorder is associated with the lack of an enzyme necessary for the normal metabolism of the amino acid phenylalanine?

Answer 18

phenylketonuria (PKU)

Question 19

Which genetic disorder is associated with an irregular shape of the red blood cells?

Answer 19

sickle cell disease

Question 20

What are the chances that two individuals with wavy hair (an incomplete trait) will have a curly-haired child? Curly hair and straight hair exhibit incomplete dominance.

Answer 20

25%

Question 21

The four o’clock flower is an example of incomplete dominance: R = red, r = white, and Rr = pink. If two hybrids are crossed, what are the chances that an offspring will have pink flowers?

Answer 21

50%

Question 22

Traits that are controlled by several sets or pairs of alleles, such as skin color and height in humans, are the result of what form of inheritance?

Answer 22

polygenic

Question 23

an example of the blending of phenotypes

Answer 23

incomplete dominance

Question 24

You have two true-breeding rose bushes, one with red flowers and one with white flowers. A cross between these two roses yields a bush with pink flowers. What condition does this demonstrate?

Answer 24

incomplete dominance

Question 25

When two or more genes with multiple alleles affect the same trait in an additive fashion, it is termed

Answer 25

polygenic inheritance

Question 26

You have two true-breeding rose bushes, one with red flowers and one with white flowers. A cross between these two roses yields a bush with white flowers that have red splotches. What condition does this demonstrate?

Answer 26

codominance

Question 27

Cold weather can change the ______ of a Himalayan rabbit.

Answer 27

phenotype

Question 28

Hydrangeas are a flowering plant with large showy blooms. When a plant is grown in aluminum-rich soil it has blue flowers. If the same plant is transplanted into soil that is lacking aluminum, the flowers produced will be pink. This is an example of

Answer 28

environmental effects.

Question 29

In peas, yellow is dominant over green in seeds. With which of these is it best to cross a yellow-seeded pea plant to determine whether it is homozygous or heterozygous?

Answer 29

a green-seeded plant

Question 30

In a testcross, an organism with a dominant phenotype, but unknown genotype is crossed with which of the following to establish its genotype?

Answer 30

homozygous recessive

Question 31

True or False? A man with AB blood type can have a child with type O.

Answer 31

False