Mendelian and Non-Mendelian Genetics

Question 1

What is an allele?

Answer 1

Gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes.

Question 2

What are autosomes?

Answer 2

Any of the non-sex chromosomes.

Question 3

What is the blending theory of inheritance?

Answer 3

Hypothetical inheritance pattern in which parental traits are blended together in the offspring to produce an intermediate physical appearance.

Question 4

What is codominance?

Answer 4

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

Question 5

What is continuous variation?

Answer 5

Inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them.

Question 6

What is a dihybrid?

Answer 6

Result of a cross between two true-breeding parents that express different traits for two characteristics.

Question 7

What is discontinuous variation?

Answer 7

Inheritance pattern in which traits are distinct and are transmitted independently of one another.

Question 8

What does dominant mean in genetics?

Answer 8

Trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait.

Question 9

What is a dominant lethal?

Answer 9

Inheritance pattern in which an allele is lethal both in the homozygote and the heterozygote; this allele can only be transmitted if the lethality phenotype occurs after reproductive age.

Question 10

What is epistasis?

Answer 10

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

Question 11

What does F1 represent?

Answer 11

First filial generation in a cross; the offspring of the parental generation.

Question 12

What does F2 represent?

Answer 12

Second filial generation produced when F1 individuals are self-crossed or fertilized with each other.

Question 13

What is a genotype?

Answer 13

Underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism.

Question 14

What does hemizygous mean?

Answer 14

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

Question 15

What does heterozygous mean?

Answer 15

Having two different alleles for a given gene on the homologous chromosome.

Question 16

What does homozygous mean?

Answer 16

Having two identical alleles for a given gene on the homologous chromosome.

Question 17

What is hybridization?

Answer 17

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

Question 18

What is incomplete dominance?

Answer 18

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

Question 19

What is the law of dominance?

Answer 19

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

Question 20

What is the law of independent assortment?

Answer 20

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 21

What is the law of segregation?

Answer 21

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

Question 22

What is linkage?

Answer 22

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 23

What is a model system?

Answer 23

Species or biological system used to study a specific biological phenomenon to be applied to other different species.

Question 24

What is a monohybrid?

Answer 24

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

Question 25

What does P0 represent?

Answer 25

Parental generation in a cross.

Question 26

What is a phenotype?

Answer 26

Observable traits expressed by an organism.

Question 27

What is the product rule in genetics?

Answer 27

Probability of two independent events occurring simultaneously can be calculated by multiplying the individual probabilities of each event occurring alone.

Question 28

What is a Punnett square?

Answer 28

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 29

What does recessive mean?

Answer 29

Trait that appears 'latent' or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive trait is expressed.

Question 30

What is a recessive lethal?

Answer 30

Inheritance pattern in which an allele is only lethal in the homozygous form; the heterozygote may be normal or have some altered, nonlethal phenotype.

Question 31

What is a reciprocal cross?

Answer 31

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 32

What does sex-linked mean?

Answer 32

Any gene on a sex chromosome.

Question 33

What is the sum rule in genetics?

Answer 33

Probability of the occurrence of at least one of two mutually exclusive events is the sum of their individual probabilities.

Question 34

What is a test cross?

Answer 34

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 35

What is a trait?

Answer 35

Variation in the physical appearance of a heritable characteristic.

Question 36

What does X-linked mean?

Answer 36

Gene present on the X, but not the Y chromosome.