BIO103 - CH14 VOCAB - patterns of inheritance

heterozygous

Having two different alleles for a given gene.

phenotype

The observable physical and physiological traits of an organism, which are determined by its genetic makeup.

genotype

The genetic makeup, or set of alleles, of an organism.

gene

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

character

An observable heritable feature that may vary among individuals.

true-breeding

Referring to organisms that produce offspring of the same variety over many generations of self-pollination.

P generation

The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance. (hint: P stands for parental)

addition rule

A rule of probability stating that the probability of any one of two or more mutually exclusive events occurring can be determined by adding their individual probabilities.

dihybrid cross

A cross between two organisms that are each heterozygous for both of the characters being followed (or the self-pollination of a plant that is heterozygous for both characters).

locus

A specific place along the length of a chromosome where a given gene is located.

allele

Any of the alternative versions of a gene that may produce distinguishable phenotypic effects.

recessive allele

An allele whose phenotypic effect is not observed in a heterozygote.

trait

One of two or more detectable variants in a genetic character.

homozygous

Having two identical alleles for a given gene.

dominant allele

An allele that is fully expressed in the phenotype of a heterozygote.

F1 generation

The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross.

F2 generation

The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation.

Punnett square

A diagram used in the study of inheritance to show the predicted genotypic results of random fertilization in genetic crosses between individuals of known genotype.

multiplication rule

A rule of probability stating that the probability of two or more independent events occurring together can be determined by multiplying their individual probabilities.

monohybrid cross

A cross between two organisms that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant).

law of segregation

Mendel's first law, stating that the two alleles in a pair segregate (separate from each other) into different gametes during gamete formation.

heredity

The transmission of traits from one generation to the next.

variation

Differences between members of the same species.

polygenic inheritance

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

pleiotropy

The ability of a single gene to have multiple effects.

complete dominance

The situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.

incomplete dominance

The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.

codominance

The situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways.

law of independent assortment

Mendel's second law, stating that each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes.

epistasis

A type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene.

epigenetics

The study of the inheritance of traits transmitted by mechanisms that DO NOT involve the nucleotide sequence (e.g. DNA).