Chapter 5

Question 1

trait (p. 184)

Answer 1

a particular version of a characteristic that is inherited, such as hair colour or blood type

Question 2

true-breeding organism (p. 184)

Answer 2

an organism that produces offspring that are genetically identical for one or more traits when self- pollinated or when crossed with another true-breeding organism for the same traits

Question 3

hybrid (p. 184)

Answer 3

the offspring of two different true- breeding plants

Question 4

cross (p. 185)

Answer 4

the successful mating of two organisms from distinct genetic lines

Question 5

P generation (p. 185)

Answer 5

the parent plants used in a cross

Question 6

F1 generation (p. 185)

Answer 6

the offspring of a P-generation cross

Question 7

monohybrid (p. 185)

Answer 7

the offspring of two different true-breeding plants that differ in only one characteristic

Question 8

monohybrid cross (p. 185)

Answer 8

a cross designed to study the inheritance of only one trait

Question 9

F2 generation (p. 185)

Answer 9

offspring of an F1 generation cross

Question 10

law of segregation (p. 186)

Answer 10

a scientific law stating that (1) organisms inherit two copies of genes, one from each parent, and (2) organisms donate only one copy of each gene to to their gametes because the genes separate during gamete formation

Question 11

allele (p. 187)

Answer 11

a specific form of a gene

Question 12

homozygous (p. 187)

Answer 12

describes an individual that carries two of the same alleles for a given characteristic

Question 13

heterozygous (p. 187)

Answer 13

describes an individual that carries two different alleles for a given characteristic

Question 14

genotype (p. 187)

Answer 14

the genetic makeup of an individual

Question 15

phenotype (p. 187)

Answer 15

an individual’s outward appearance with respect to a specific characteristic

Question 16

dominant allele (p. 187)

Answer 16

the allele that, if present, is always expressed

Question 17

recessive allele (p. 187)

Answer 17

the allele that is expressed only if it is not in the presence of the dominant allele, that is, if the individual is homozygous for the recessive allele

Question 18

Punnett square (p. 188)

Answer 18

a diagram that summarizes every possible combination of each allele from each parent; a tool for determining the probability of a single offspring having a particular genotype

Question 19

probability (p. 188)

Answer 19

the likelihood that an outcome will occur if it is a matter of chance

Question 20

test cross (p. 190)

Answer 20

a cross used to determine the genotype of an individual expressing a dominant trait

Question 21

complete dominance (p. 194)

Answer 21

a situation where an allele will determine the phenotype, regardless of the presence of another allele

Question 22

incomplete dominance (p. 194)

Answer 22

a situation where neither allele dominates the other and both have an influence on the individual; results in partial expression of both traits

Question 23

co-dominance (p. 195)

Answer 23

a situation where both alleles are expressed fully to produce offspring with a third phenotype

Question 24

pedigree (p. 197)

Answer 24

a diagram of an individual’s ancestors used in human genetics to analyze the Mendelian inheritance of a certain trait; also used for selective breeding of plants and animals

Question 25

autosomal inheritance (p. 200)

Answer 25

inheritance of alleles located on autosomal (non-sex) chromosomes

Question 26

sex-linked (p. 200)

Answer 26

describes an allele that is found on one of the sex chromosomes, X or Y, and when passed on to offspring is expressed

Question 27

X-linked (p. 200)

Answer 27

phenotypic expression of an allele that is found on the X chromosome

Question 28

Y-linked (p. 200)

Answer 28

phenotypic expression of an allele that is found on the Y chromosome

Question 29

mutation (p. 204)

Answer 29

a change in the genetic code of an allele; the change may have a positive effect, a negative effect, or no effect

Question 30

carrier testing (p. 204)

Answer 30

a genetic test that determines whether an individual is heterozygous for a given gene that results in a genetic disorder

Question 31

genetic screening (p. 204)

Answer 31

tests used to identify the presence of a defective allele that leads to a genetic disorder

Question 32

phenylketonuria (PKU) (p. 205)

Answer 32

an autosomal, recessive, inherited genetic disorder that results in the accumulation of phenylalanine in the tissues and blood

Question 33

dihybrid cross (p. 210)

Answer 33

a cross that involves two genes, each consisting of heterozygous alleles

Question 34

law of independent assortment (p. 210)

Answer 34

if genes are located on separate chromosomes, they will be inherited independently of one another

Question 35

product law (p. 213)

Answer 35

the probability of two independent random events both occurring is the product of the individual probabilities of the events

Question 36

discontinuous variation (p. 213)

Answer 36

when the expression of the products of one gene has no bearing on the expression of the products of a second gene

Question 37

continuous variation (p. 214)

Answer 37

when the product of one gene is affected by the product of another gene, the gene products may be additive, or one product may negate another product

Question 38

additive allele (p. 214)

Answer 38

an allele that has a partial influence on a phenotype