Chapter 14

Question 1

“Blending” hypothesis

Answer 1

The idea that genetic material contributed by the two parents mixes

Question 2

“Particulate” hypothesis

Answer 2

The gene idea.

Question 3

Character

Answer 3

A heritable feature that varies among individuals, such as flower color.

Question 4

Trait

Answer 4

Each variant for a character

Question 5

Stamens

Answer 5

Pollen-producing organs

Question 6

Carpel

Answer 6

An egg-bearing organ

Question 7

True-breeding

Answer 7

Referring to organisms that produce offspring of the same variety over many generations of self-pollination.

Question 8

Hybridization

Answer 8

Mating, or crossing, of two true-breeding varieties

Question 9

P generation

Answer 9

Parental generation

Question 10

F1 generation

Answer 10

First filial generation

Question 11

F2 generation

Answer 11

Second filial generation

Question 12

Alleles

Answer 12

Alternative versions of a gene

Question 13

Locus

Answer 13

The location of a gene in a chromosome

Question 14

For each character, an organism inherits two copies (that is, two alleles) of a gene, one from each parent.

Answer 14

True

Question 15

Dominant allele

Answer 15

Determines the organism’s appearance.

Question 16

Law of segregation

Answer 16

States that the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes.

Question 17

Homozygous

Answer 17

An organism that has a pair of identical alleles for a character

Question 18

Heterozygous

Answer 18

An organism that has two different alleles for a gene

Question 19

Phenotype

Answer 19

Observable traits

Question 20

Genotype

Answer 20

Genetic makeup

Question 21

Testcross

Answer 21

Breeding an organism of unknown genotype with a recessive homozygote

Question 22

Mendel derived the law of segregation from experiments in which he followed only a single character, such as flower color.

Answer 22

True

Question 23

Monohybrid

Answer 23

An organism that is heterozygous with respect to a single gene of interest.

Question 24

Monohybrid cross

Answer 24

A cross between two organisms that are heterozygous for the character being followed.

Question 25

Mendel identified the law of independent assortment by following two characters at the same time, such as seed color and seed shape.

Answer 25

True

Question 26

Dihybrids

Answer 26

Individuals heterozygous for the two characters being followed in the cross.

Question 27

Dihybrid cross

Answer 27

A cross between F1 dihybrids

Question 28

Law of independent assortment

Answer 28

States that two or more genes assort independently— that is, each pair of alleles segregates independently of each other pair of alleles— during gamete formation.

Question 29

Incomplete dominance

Answer 29

Neither allele is completely dominant, and the F1 hybrids have a phenotype somewhere between those of the two parental varieties.

Question 30

Codominance

Answer 30

The two alleles each affect the phenotype in separate, distinguishable ways.

Question 31

Pleiotropy

Answer 31

The property of genes having multiple phenotypic effects.

Question 32

Epistasis

Answer 32

The phenotypic expression of a gene at one locus alters that of a gene at a second locus.

Question 33

Quantitative character

Answer 33

A heritable feature that varies continuously over a range rather than in an either-or fashion

Question 34

Polygenic inheritance

Answer 34

An additive effect of two or more genes on a single phenotypic character.

Question 35

A genotype generally is not associated with a rigidly defined phenotype, but rather with a range of phenotypic possibilities due to environmental influences.

Answer 35

True

Question 36

Multifactorial

Answer 36

Many factors, both genetic and environmental, collectively influence phenotype.

Question 37

Carriers

Answer 37

Heterozygotes; they may transmit the recessive allele to their offspring.

Question 38

The probability of passing on recessive traits increases greatly if the man and woman are close relatives.

Answer 38

True

Question 39

The most common lethal genetic disease in the United States is ________, which strikes one out of every 2,500 people of European descent but is much rarer in other groups.

Answer 39

Cystic fibrosis

Question 40

The most common inherited disorder among people of African descent is __________, which affects one out of 400 African—Americans.

Answer 40

Sickle-cell disease

Question 41

Sickle cell is caused by…

Answer 41

The substitution of a single amino acid in the hemoglobin protein of red blood cells.

Question 42

Achondroplasia is a trait for which the recessive allele is much more prevalent than the corresponding dominant allele.

Answer 42

True

Question 43

Dominant alleles that cause a lethal disease are much less common than recessive alleles that have lethal effects.

Answer 43

True

Question 44

Huntington’s disease is caused by a lethal dominant allele that has no obvious phenotypic effect until the individual is about 35 to 45 years old.

Question 45

Heart disease, diabetes, cancer, alcoholism, certain mental illnesses such as schizophrenia and bipolar disorder, and many other diseases are multifactorial.

Answer 45

True

Question 46

Amniocentesis

Answer 46

Technique used to help determine whether the developing fetus has Tay-Sachs disease.

Question 47

Chorionic villus sampling (CVS)

Answer 47

Technique where a sample of placenta is used to detect genetic disorders.

Question 48

CVS is faster than amniocentesis and can be performed earlier.

Answer 48

True

Question 49

Ultrasound

Answer 49

Technique where reflected sound waves are used to produce an image of the fetus by a simple noninvasive procedure.

Question 50

Fetoscopy

Answer 50

Technique where a needle-thin tube containing a viewing scope and fiber optics is inserted into the uterus.