Mendelian and Modern Genetics

Vocabulary practice flashcards covering classical Mendelian inheritance, complex genetic interactions, pedigree analysis, and modern molecular genetics techniques.

Gregor Mendel

An Augustinian monk at St Thomas Abbey in Brno of the Czech Republic who studied garden peas, published his pioneering genetics paper in 1866, and whose experiments were distinguished by being quantitative, controlled, and elegantly designed.

Cross (or Mating)

Sexual reproduction between two organisms.

Hybrid

A cross between two parents that differ in some trait.

Phenotype

The observable physical or biochemical properties of an organism.

Genotype

The genetic makeup of an organism, referring to the specific alleles it contains.

True Breeding

A strain or organism that consistently transmits a specific trait unchanged to all offspring across generations when selfed or bred with an identical individual (homozygous).

Parental Strains ($P_0$ or $F_0$)

The initial generation of true-breeding individuals mated to begin a genetic cross.

$F_1$ Generation

The first filial generation; the immediate offspring produced from crossing the parental ($P_0$) strains.

$F_2$ Generation

The second filial generation; the offspring resulting from the selfing or intercrossing of individuals from the $F_1$ generation.

Dominant

An allele or phenotype that masks the expression of an alternative allele when present in a heterozygote.

Recessive

An allele or phenotype whose effect is masked in the presence of a dominant allele and is only expressed when homozygous.

Gamete

A reproductive sex cell that carries exactly one genetic determinant (one allele) for each trait.

Zygote

A fertilized egg resulting from the fusion of two gametes, carrying two genetic determinants for each trait.

Mendel's Principle of Segregation

The rule stating that each individual possesses two genetic determinants for each gene, which segregate randomly into gametes such that each gamete receives only one determinant.

Backcross

The mating of an $F_1$ generation individual back to one of the parental strains (usually the recessive parental strain).

Test Cross

The mating of an individual of unknown genotype (or an $F_1$ individual) to a homozygous recessive individual to determine the gametic ratio or genotype.

Gene

A hereditary factor or unit of DNA that influences a specific characteristic or trait.

Allele

A particular variant or alternative form of a specific gene.

Homozygous

Having two identical alleles for a particular gene.

Heterozygous

Having two different alleles for a particular gene.

Dihybrid Cross

A cross between parental organisms that differ in two specific, observable traits.

Principle of Independent Assortment

The rule stating that alleles of different genes segregate and assort into gametes independently of one another during meiosis.

Incomplete Dominance

A form of intermediate inheritance where neither allele is completely dominant, producing a heterozygous phenotype that is an intermediate blend (such as pink snapdragons resulting from red and ivory parents).

Antigen

A substance (such as a cell-surface polysaccharide) recognized as foreign by the immune system or capable of binding specific antibodies.

Antibody

A protein in the blood produced by the immune system that identifies, binds, and targets foreign substances for destruction.

ABO Blood Group System

A human blood group system determined by three alleles ($I^A$, $I^B$, and $I^0$); $I^A$ and $I^B$ synthesize distinct polysaccharide antigens, whereas $I^0$ is defective and produces no additional polysaccharide.

Codominance

A condition in which both alleles of a gene pair in a heterozygote are fully and simultaneously expressed without blending, as observed with the $I^A$ and $I^B$ alleles producing AB blood type.

Conditional Mutation

A mutation whose phenotypic effects are only expressed under specific circumstances, such as particular environmental factors or combinations with other genes.

Temperature-Sensitive Mutation

A conditional mutation where phenotype depends on temperature; exemplified in Siamese cats whose coat pigment enzyme is only active in cooler body extremities such as the paws, ears, and tail.

Epistasis

A form of gene interaction where one gene alters or masks the phenotypic expression of another gene, such as eye color in Drosophila melanogaster producing a $9:3:3:1$ ratio featuring a novel white double-homozygous mutant phenotype.

Pedigree

A standardized diagram depicting the phenotypic history and familial relationships of individuals across several generations.

Carrier

An individual who is heterozygous for a recessive allele, possessing the allele without expressing the mutant or diseased phenotype.

Dominant Pedigree

A pedigree pattern tracking a dominant trait (such as widow's peak, $W$) where affected individuals appear in every generation and there are no unaffected carriers.

DNA Microarray

A glass slide with an ordered pattern of known DNA sequences synthesized by PCR, used to hybridize with fluorescently labeled DNA samples to detect differences in genetic composition or mutations.

BRCA1 and BRCA2

Genes associated with hereditary breast and ovarian cancer susceptibility that can be directly screened for mutations using modern DNA testing.