Definitions

Question 1

What is an allele?

Answer 1

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

Question 2

Define codominance.

Answer 2

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

Question 3

What is continuous variation?

Answer 3

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

Question 4

What does dihybrid refer to?

Answer 4

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

Question 5

Define 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

What is a dominant trait?

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

What is epistasis?

Answer 7

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

Question 8

What does F1 stand for?

Answer 8

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

Question 9

What is F2?

Answer 9

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

Question 10

Define genotype.

Answer 10

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

Question 11

What does hemizygous mean?

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

What is heterozygous?

Answer 12

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

Question 13

Define homozygous.

Answer 13

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

Question 14

What is hybridization?

Answer 14

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

Question 15

Define incomplete dominance.

Answer 15

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

Question 16

What is the law of dominance?

Answer 16

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

Question 17

What does the law of independent assortment state?

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

Define the 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

What is 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

What is a model system?

Answer 20

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

Question 21

Define monohybrid.

Answer 21

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

Question 22

What is the parental generation (P)?

Answer 22

The first generation in a cross

Question 23

Define phenotype.

Answer 23

The observable traits expressed by an organism

Question 24

What is a 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

What is a recessive trait?

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

What is a 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

Define 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

What is a 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

What is a trait?

Answer 29

A variation in an inherited characteristic

Question 30

Define wild type.

Answer 30

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

Question 31

What does X-linked mean?

Answer 31

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