Genetics Vocabulary

These flashcards cover key vocabulary terms related to genetics, heredity, and inheritance patterns.

Trait

A distinct variant of a phenotypic character of an organism.

Continuous variation

Variation in a trait that falls along a continuum.

Discontinuous variation

Variation in a trait where characteristics fall into distinct categories.

Hybridization

The mating, or crossing, of two true-breeding varieties.

Genes

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA.

Heterozygous

Having two different alleles for a given gene.

Law of segregation

Mendel's first law, stating that allele pairs separate during gamete formation; that is, during meiosis, the paired alleles separate.

Dominant

An allele that is fully expressed in a heterozygote.

Recessive

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

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.

Punnet 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.

Pedigree

A diagram of a family tree with conventional symbols, showing the occurrence of heritable characters in parents and offspring over multiple generations.

Dihybrid crosses

A cross between two organisms that are each heterozygous for both of the characters being followed

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.

Completed dominance

A 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.

Co-dominance

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

Polygene 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.

Chromosomal theory of inheritance

A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.

Linkage

Refers to when different traits are inherited together more often than they would be by chance; it is assumed that these traits are linked on the same chromosome.

Wild type

The phenotype most commonly observed in natural populations; also refers to the individual with that phenotype.

Variants

An individual, thing, or action differing from others of the same type.

Autosomes

A chromosome that is not directly involved in determining sex; not a sex chromosome.

Allosomes

A chromosome that determines sex; a sex chromosome.

Autosomal dominant disorder

A pattern of inheritance in which an affected individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes

Autosomal recessive disorder

Two copies of an abnormal gene must be present in order for the disease or trait to develop.

S(sex)-linked

A gene located on either sex chromosome. Most sex-linked genes are on the X chromosome and show distinctive patterns of inheritance; there are very few genes on the Y chromosome.