AP Bio - Chapter 11 + 12 - Mendel and the Chromosomal Basis of Inheritance.

Characters

Varieties with distinct heritable features (such as flower color).

Traits

Character variants (such as purple or white flowers).

True-Breeding

Plants that produce offspring of the same variety when the self-pollinate.

Hybridization

The mating of two contrasting, true-breeding varieties.

P Generation

The true-breeding parents.

F1 Generation

The hybrid offspring of the P generation.

F2 Generation

The offspring resulting from the self-pollination or cross-pollination of the F1 generation.

Alleles

Alternative versions of genes.

Law of Segregation

Law that states that the two alleles for a heritable character separate during gamete formation and end up in different gametes.

Homozygous

An organism with two identical alleles for a character is said to be __________ for the gene controlling that character.

Heterozygous

An organism that has two different alleles for a character is said to be ____________ for the gene controlling that character.

Phenotype

An organism’s physical appearance.

Genotype

An organism’s genetic makeup.

Testcross

Breeding a mystery individual with a homozygous recessive individual.

Monohybrids

The F1 offspring produced, they are individuals that are heterozygous for one character.

Monohybrid Cross

A cross between monohybrids.

Dihybrids

Individuals that result from the cross between two true-breeding parents that differ in two characters, they are heterozygous for both characters.

Dihybrid Cross

Cross between two F1 dihybrids.

Law of Independent Assortment

Law that states that each pair of alleles segregates independently of each other pair of alleles during gamete formation. Applies to genes on different nonhomologous chromosomes or those very far apart on the same chromosome.

Multiplication Rule

Rule that states that the probability that two or more independent events will occur together is the product of their individual probabilities.

Addition Rule

Rule that states that the probability that any one of two or more mutually exclusive events will occur is calculated by adding together their individual probabilties.

Complete Dominance

Type of dominance that occurs when phenotypes of the heterozygote and dominant homozygote are idenitcal.

Incomplete Dominance

Type of dominance where the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties.

Codominance

Type of dominance where two dominant alleles affect the phenotype in separate, distinguishable ways.

Pleiotropy

Property of most genes where they have multiple phenotypic effects.

Epistasis

A gene at one locus alters the phenotypic expression of a gene at a second locus.

Quantitative Characters

Characters that are those that vary in the population among a continuum. Usually indicates polygenic inheritance.

Polygenic Inheritance

An additive effect of two or more genes on a single phenotype.

Pedigree

A family tree that describes the interrelationships of parents and children through generations.

Carriers

Heterozygous individuals who carry the recessive allele but are phenotypically normal.

Chromosome Theory of Inheritance

Theory that states that mendelian genes have specific loci on chromosomes, and that chromosomes undergo segregation and independent assortment.

Wild-Type

Normal phenotypes that are common in a species.

Mutants

Organisms that have alternative traits to the normal.

Sex-Linked Gene

A gene that is located on either sex chromosome.

X-Linked Genes

Genes on the X chromosome.

Barr Body

In mammalian females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development, and condenses into a ____ ____.

Genetic Recombination

The production of offspring with combinations of traits differing from either parent.

Parental Types

Offspring with a phenotype matching one of the parental phentypes.

Recombinants

Offspring with nonparental phenotypes (new combinations of traits).

Linkage Map

A genetic map of a chromosome based on recombination frequencies.

Map Units

Distances between genes can be expressed as this unit, one unit represents a 1% recombination frequency.

Cytogenic Maps

Indicate the positions of genes with respect to chromosomal features.

Nondisjunction

Pairs of homologous chromosomes do not separate normally during meiosis.

Aneuploidy

Results from the fertilization of gametes in which nondisjunction occured.

Monosomic

Zygote that has only one copy of a particular chromosome.

Trisomic

A zygote that has three copies of a particular chromosome.

Polyploidy

A condition in which an organism has more than two complete sets of chromosomes.

Deletion

Removal of a chromosomal segment, results in a change of chromosomal structure.

Duplication

Repetition of a segment, results in a change of chromosomal structure.

Inversion

Reversal of the orientation of a segment within a chromosome, results in a change of chromosomal structure.

Translocation

Movement of a segment from one chromosome to another, results in a change of chromosomal structure.