CH 10 Patterns of inheritance

Vocabulary flashcards covering key genetics concepts from the notes.

Gene

A portion of DNA whose sequence of nucleotides encodes a protein or trait; the proteins expressed in cells determine many characteristics.

DNA

The molecule that carries genes; composed of nucleotides A, C, G, and T.

Chromosome

A long strand of DNA wrapped around histone proteins; contains many different genes.

Diploid

Cells with two sets of chromosomes; humans have 46 chromosomes, 23 from each parent.

Allele

Alternative forms of a gene that encode information for the same trait; may be identical or different versions.

Homologous chromosomes

Pairs of chromosomes that carry the same genes; may carry different alleles.

Locus

The specific location of a gene on a chromosome.

Genotype

An individual’s two alleles for one gene.

Phenotype

The observable physical appearance or trait, determined by how alleles interact.

Homozygous dominant

Two dominant alleles for a gene (e.g., AA).

Homozygous recessive

Two recessive alleles for a gene (e.g., aa).

Heterozygous

One dominant and one recessive allele for a gene (e.g., Aa).

Dominant allele

An allele that exerts its effect whenever it is present.

Recessive allele

An allele whose effect is masked by a dominant allele; often encodes a nonfunctional protein.

True breeding

Parental generation that would produce offspring identical to itself if self-fertilized.

Hybrid

Offspring from crossing true-breeding strains; outwardly resembles one parent and produces mixed offspring.

Punnett square

A diagram showing gamete formation and fertilization to predict offspring genotypes and phenotypes.

Monohybrid cross

Cross involving a single gene; typically yields a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio.

Test cross

Cross with a homozygous recessive individual to reveal an unknown genotype of the other parent.

Dihybrid cross

Cross tracking two genes; demonstrates independent assortment; can yield 9:3:3:1 phenotypic ratio.

Law of Segregation

The two alleles of each gene segregate during gamete formation.

Law of Independent Assortment

Genes on different chromosomes assort independently during gamete formation.

Sex-linked genes

Genes located on the sex chromosomes (X or Y) with inheritance patterns that differ by sex.

X-linked inheritance

Genes on the X chromosome; males have one X allele and express it; females have two X alleles.

X-inactivation

In XX individuals, one X chromosome is randomly inactivated to prevent double gene dosage.

Environment and phenotype

Environmental factors can alter phenotype, e.g., pigment production in Siamese cats depends on temperature.

Polygenic trait

Trait controlled by more than one gene, resulting in a range of phenotypes (e.g., height, skin color).

Incomplete dominance

Heterozygotes show an intermediate phenotype rather than one being completely dominant.