Chapter 14_DV

Question 1

What is the ‘blending’ hypothesis in genetics?

Answer 1

The idea that genetic material from the two parents blends together.

Question 2

What contradicts the blending hypothesis?

Answer 2

Everyday predictions, breeding experiments, and reappearance of traits after skipping a generation.

Question 3

What is the ‘particulate’ hypothesis?

Answer 3

The idea that parents pass on discrete heritable units (genes) that retain their separate identities in offspring.

Question 4

Who documented the particulate mechanism through experiments?

Answer 4

Mendel documented it through his experiments with garden peas.

Question 5

What was Mendel’s approach to studying heredity?

Answer 5

He used a scientific approach, conducting carefully planned breeding experiments.

Question 6

What advantages do pea plants offer for genetic study?

Answer 6

Distinct heritable features, controlled mating, short generation time, and large number of offspring.

Question 7

What does a heritable trait refer to?

Answer 7

A trait passed from parent to offspring.

Question 8

What is hybridization in Mendel’s experiments?

Answer 8

The process of mating two contrasting, true-breeding varieties.

Question 9

What is the parental generation in Mendel’s experiments called?

Answer 9

The P generation.

Question 10

What are the offspring of the P generation called?

Answer 10

The F1 generation.

Question 11

What was the ratio of purple to white flowers in the F2 generation?

Answer 11

Approximately three to one.

Question 12

What did Mendel call the trait that was expressed in the F1 hybrids?

Answer 12

Dominant trait.

Question 13

What is a recessive trait?

Answer 13

A trait that is masked in the presence of a dominant trait.

Question 14

What is a gene according to Mendel’s findings?

Answer 14

What Mendel called a ‘heritable factor’ is now known as a gene.

Question 15

What are alleles?

Answer 15

Alternative versions of genes that account for variations in inherited characters.

Question 16

What does it mean for an organism to be homozygous?

Answer 16

It has two identical alleles for a character.

Question 17

What does it mean for an organism to be heterozygous?

Answer 17

It has two different alleles for a gene.

Question 18

What is the phenotype of an organism?

Answer 18

The physical appearance of an organism.

Question 19

What is the genotype of an organism?

Answer 19

The genetic makeup of an organism.

Question 20

What is a testcross?

Answer 20

Breeding a mystery individual with a homozygous recessive individual to determine its genotype.

Question 21

What is the law of independent assortment?

Answer 21

The law stating that each pair of alleles segregates independently of each other pair during gamete formation.

Question 22

What is a monohybrid cross?

Answer 22

A cross between individuals heterozygous for one character.

Question 23

What is a dihybrid cross?

Answer 23

A cross between individuals heterozygous for two characters.

Question 24

What does the multiplication rule in genetics state?

Answer 24

The probability that two or more independent events will occur together is the product of their individual probabilities.

Question 25

What does the addition rule in genetics state?

Answer 25

The probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities.

Question 26

What is the significance of Mendel’s laws of segregation and independent assortment?

Answer 26

They reflect the rules of probability in genetic inheritance.

Question 27

What is the relationship between genotype and phenotype in inheritance?

Answer 27

It is often more complex than predicted by simple Mendelian genetics.

Question 28

What is the relationship between genotype and phenotype in inheritance patterns?

Answer 28

The relationship is rarely as simple as in Mendelian genetics ## Footnote Many heritable characters are not determined by only one gene with two alleles

Question 29

What are the basic principles that apply even to complex patterns of inheritance?

Answer 29

Segregation and independent assortment ## Footnote These principles are foundational in genetics

Question 30

What can cause inheritance patterns of a single gene to deviate from simple Mendelian patterns?

Answer 30

The following situations: * Alleles are not completely dominant or recessive * A gene has more than two alleles * A gene produces multiple phenotypes

Question 31

What occurs in complete dominance?

Answer 31

Phenotypes of the heterozygote and dominant homozygote are identical

Question 32

Define incomplete dominance.

Answer 32

The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties

Question 33

What is codominance?

Answer 33

Two dominant alleles affect the phenotype in separate, distinguishable ways ## Footnote Example: Human MN blood group

Question 34

What is an example of incomplete dominance in plants?

Answer 34

Snapdragon color ## Footnote Red and white parents produce pink hybrids

Question 35

How do dominance/recessiveness relationships of alleles depend?

Answer 35

On the level at which we examine the phenotype

Question 36

What is pleiotropy?

Answer 36

Most genes have multiple phenotypic effects

Question 37

What is epistasis?

Answer 37

A gene at one locus alters the phenotypic expression of a gene at a second locus

Question 38

Give an example of a polygenic trait.

Answer 38

Skin color in humans

Question 39

What is the norm of reaction?

Answer 39

The phenotypic range of a genotype influenced by the environment

Question 40

What is a pedigree?

Answer 40

A family tree that describes the interrelationships of parents and children across generations

Question 41

What are carriers in genetics?

Answer 41

Heterozygous individuals who carry the recessive allele but are phenotypically normal

Question 42

What is cystic fibrosis?

Answer 42

The most common lethal genetic disease in the United States, caused by a defective chloride transport channel

Question 43

What is sickle-cell disease?

Answer 43

A genetic disorder caused by the substitution of a single amino acid in hemoglobin

Question 44

What is achondroplasia?

Answer 44

A form of dwarfism caused by a rare dominant allele

Question 45

What is Huntington’s disease?

Answer 45

A degenerative disease of the nervous system that appears later in life

Question 46

What is multifactorial inheritance?

Answer 46

Inheritance patterns influenced by both genetic and environmental factors

Question 47

What is the purpose of genetic counseling?

Answer 47

To provide information to prospective parents concerned about a family history of specific diseases

Question 48

What is amniocentesis?

Answer 48

A procedure that removes liquid that bathes the fetus for testing

Question 49

What is chorionic villus sampling (CVS)?

Answer 49

A technique that removes a sample of the placenta for testing

Question 50

What is newborn screening?

Answer 50

Tests performed at birth to detect some genetic disorders