Chapter 8: Patterns of Inheritance

Question 1

allele

Answer 1

one of two or more variants of a gene that determines a particular trait for a characteristic

Question 2

codominance

Answer 2

in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic

Question 3

continuous variation

Answer 3

a variation in a characteristic in which individuals show a range of traits with small differences between them

Question 4

dihybrid

Answer 4

the result of a cross between two true-breeding parents that express different traits for two characteristics

Question 5

discontinuous variation

Answer 5

a variation in a characteristic in which individuals show two, or a few, traits with large differences between them

Question 6

dominant

Answer 6

describes a trait that masks the expression of another trait when both versions of the gene are present in an individual

Question 7

epistasis

Answer 7

an interaction between genes such that one gene masks or interferes with the expression of another

Question 8

F1

Answer 8

the first filial generation in a cross; the offspring of the parental generation

Question 9

F2

Answer 9

the second filial generation produced when F1 individuals are self-crossed or fertilized with each other

Question 10

genotype

Answer 10

the underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism

Question 11

hemizygous

Answer 11

the presence of only one allele for a characteristic, as in X-linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant

Question 12

heterozygous

Answer 12

having two different alleles for a given gene on the homologous chromosomes

Question 13

homozygous

Answer 13

having two identical alleles for a given gene on the homologous chromosomes

Question 14

hybridization

Answer 14

the process of mating two individuals that differ, with the goal of achieving a certain characteristic in their offspring

Question 15

incomplete dominance

Answer 15

in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype

Question 16

law of dominance

Answer 16

in a heterozygote, one trait will conceal the presence of another trait for the same characteristic

Question 17

law of independent assortment

Answer 17

genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur

Question 18

law of segregation

Answer 18

paired unit factors (i.e., genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors

Question 19

linkage

Answer 19

a phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together

Question 20

model system

Answer 20

a species or biological system used to study a specific biological phenomenon to gain an understanding that will be applied to other species

Question 21

monohybrid

Answer 21

the result of a cross between two true-breeding parents that express different traits for only one characteristic

Question 22

parental generation (P)

Answer 22

the first generation in a cross

Question 23

phenotype

Answer 23

the observable traits expressed by an organism

Question 24

Punnett square

Answer 24

a visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively, and the possible zygotic genotypes are recombined at each box in the grid

Question 25

recessive

Answer 25

describes a trait whose expression is masked by another trait when the alleles for both traits are present in an individual

Question 26

reciprocal cross

Answer 26

a paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross

Question 27

recombination

Answer 27

the process during meiosis in which homologous chromosomes exchange linear segments of genetic material, thereby dramatically increasing genetic variation in the offspring and separating linked genes

Question 28

test cross

Answer 28

a cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait

Question 29

trait

Answer 29

a variation in an inherited characteristic

Question 30

wild type

Answer 30

the most commonly occurring genotype or phenotype for a given characteristic found in a population

Question 31

X-linked

Answer 31

a gene present on the X chromosome, but not the Y chromosome