Chapter 13

Front 1

Genetics

Back 1

The field of study concerned with the inheritance of traits.

Front 2

Heredity

Back 2

The transmission of traits from parents to offspring via genetic information.

Front 3

Trait

Back 3

Any heritable characteristic of an individual.

Front 4

Model Organism

Back 4

An organism selected for intensive scientific study based on features that make it easy to work with in the hope that findings will apply to other species.

Front 5

Pollen Grain

Back 5

In seed plants, a male gametophyte enclosed within a protective coat.

Front 6

Cross-fertilization

Back 6

A mating that combines gametes from different individuals, as opposed to combining gametes from the same individual.

Front 7

Phenotype

Back 7

The detectable physical and physiological traits that determine an individual's genetic make up. Also the specific trait associated with a particular allele.

Front 8

Pure Line

Back 8

In animal or plant breeding, a strain of individuals that produce offspring identical to themselves when self-pollinated or crossed to another member of the same population. Pure lines are homozygous for most, if not all, genetic loci.

Front 9

Hybrid

Back 9

The offspring of parents from two different strains, populations, or species.

Front 10

Parental Generation

Back 10

The adult organisms used in the first experimental cross in a formal breeding experiment.

Front 11

F1 Generation

Back 11

First filial generation. The first generation of offspring produced from a mating, the offspring of the parental generation.

Front 12

Monohybrid Cross

Back 12

A mating between two parents that are both heterozygous for a given gene.

Front 13

Recessive

Back 13

Referring to an allele whose phenotypic effect is observed only in homozygous individuals.

Front 14

Dominant

Back 14

Referring to an allele that determines the phenotype of a heterozygous individual.

Front 15

Huntington's Disease

Back 15

A degenerative brain disease of humans caused by an autosomal dominant allele.

Front 16

Reciprocal Cross

Back 16

A breeding experiment in which the mother's and father's phenotypes are the reverse of that examined in a previous breeding experiment.

Front 17

Particulate Inheritence

Back 17

The observation that genes from two parents do not blend together to form a new physical entity in offspring, but instead remain separate or particle-like.

Front 18

Genotype

Back 18

All of the alleles of every gene present in a given individual. May refer specifically to the alleles of a particular set of genes under study.

Front 19

Principle of Segregation

Back 19

The concept that each pair of hereditary elements (alleles of the same gene) separate from each other during the formation of offspring. One of Mendel's two principles of genetics.

Front 20

Homozygous

Back 20

Having two identical alleles of a certain gene.

Front 21

Heterozygous

Back 21

Having two different alleles of a certain gene.

Front 22

Punnett Square

Back 22

A diagram that depicts the genotypes and phenotypes that should appear in offspring of a certain cross. Invented by R.C. Punnett.

Front 23

Genetic Model

Back 23

A set of hypotheses that explain how a certain trait is inherited.

Front 24

Dihybrid Cross

Back 24

A mating between two parents that are heterozygous for both of the two genes being studied.

Front 25

Principle of Independent Assortment

Back 25

The concept that each pair of hereditary elements (alleles of the same gene) behaves independently of other genes during meiosis. One of Mendel's two principles of genetics.

Front 26

Phenotypic Ratios of a Dihybrid Cross

Back 26

9:3:3:1

Front 27

Testcross

Back 27

The breeding of an individual of an unknown genotype with an individual having only recessive alleles for the traits of interest in order to infer the unknown genotype from the phenotypic ratios seen in offspring.

Front 28

Phenotypic Ratios of a Testcross

Back 28

1:1:1:1

Front 29

Gene

Back 29

A section of DNA that encodes information for building one or more related polypeptides or functional RNA molecules along with the regulatory sequences required for its transcription.

Front 30

Allele

Back 30

A particular version of a gene.

Front 31

Locus

Back 31

A gene's physical location on a chromosome.

Front 32

Chromosome Theory of Inheritance

Back 32

The principle that genes are located on chromosomes and that patterns of inheritance are determined by the behaviour of chromosomes during meiosis.

Front 33

Wild Type

Back 33

The most common phenotype seen in a population; especially the most common phenotype in wild populations compared with inbred strains of the same species.

Front 34

Mutation

Back 34

Any change in the hereditary material of an organism.

Front 35

Mutant

Back 35

A carrier of a mutation.

Front 36

X-linked Inheritance

Back 36

Inheritance patterns for genes located on the mammalian X chromosome. Also called X-linkage.

Front 37

Y-linked Inheritance

Back 37

Inheritance patterns for genes located on the mammalian Y chromosome. Also called Y-linkage.

Front 38

Sex-linked Inheritance

Back 38

Inheritance patterns observed in genes carried on sex chromosomes, so females and males have different numbers of alleles of a gene and may pass its trait only to one sex of offspring. Also called sex-linkage.

Front 39

Autosomal Inheritance

Back 39

The inheritance patterns that occur when genes are located on autosomes rather than on sex chromosomes.

Front 40

Thomas Hunt Morgan

Back 40

Fruit fly eye colour experiment. Showed that genes are located on chromosomes. Also showed that linked genes are inherited together unless crossing over occurs.

Front 41

Linkage

Back 41

A physical association between two genes because they are on the same chromosome; the inheritance patterns resulting from this association. An exception from independent assortment.

Front 42

Recombinant

Back 42

Possessing a new combination of alleles. May refer to a single chromosome or DNA molecule or to an entire organism. Happens when crossing over occurs.

Front 43

Genetic Map

Back 43

An ordered list of genes on a chromosome that indicates their relative distances from each other. Also called a linkage map or a meiotic map.

Front 44

Incomplete Dominance

Back 44

An inheritance pattern in which the heterozygote phenotype is a blend or combination of both homozygote phenotypes.

Front 45

How to use centiMorgan (cM)

Back 45

Genes that are 50cM apart cross over 50% of the time.

Front 46

Codominance

Back 46

An inheritance pattern in which heterozygotes exhibit both of the traits seen in either kind of homozygous individual.

Front 47

Multiple Allelism

Back 47

In a population, the existence of more than two alleles of the same gene.

Front 48

Polymorphism

Back 48

The occurrence of more than two distinct phenotypes of a trait in a population due to multiple allelism.

Front 49

Pleiotropy

Back 49

The ability of a single gene to affect more than one phenotypic trait.

Front 50

Marfan Syndrome

Back 50

A human syndrome involving increased height, long limbs and fingers, an abnormally shaped chest, and heart disorders. Probably caused by mutation in one pleiotropic gene.

Front 51

Phenylketonuria (PKU)

Back 51

A disease caused by the inability to process the amino acid phenylalanine.

Front 52

Discrete Trait

Back 52

An inherited trait that exhibits distinct phenotypic forms rather than the continuous variation characteristic of a quantitative trait such as body height.

Front 53

Quantitative Trait

Back 53

A heritable feature that exhibits phenotypic variation along a smooth, continuous scale of measurement (like height), rather than the distinct forms characteristic of discrete traits. Have a normal distribution on a graph.

Front 54

Polygenic Inheritance

Back 54

The inheritance patterns that result when many genes influence one trait.

Front 55

Gene-by-gene Interaction

Back 55

In discrete traits, the phenotype associated with an allele depends on which alleles are present at another gene.

Front 56

Gene-by-environment Interaction

Back 56

Phenotype influenced by environment experienced by individual (i.e. plant height and sun exposure).

Front 57

Pedigree

Back 57

A family tree of parents and offspring, showing inheritance of particular traits of interest.

Front 58

Carrier

Back 58

A heterozygous individual carrying a normal allele and a recessive allele for an inherited trait; does not display the phenotype of the trait but can pass the recessive gene to the offspring.

Front 59

Hemophilia

Back 59

A human disease, caused by an X-linked recessive allele, that is characterized by defects in the blood-clotting system.