DNA & Genetics – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering key concepts from DNA, genetics, and evolution.

Genetics

The study of heredity—the passing of traits from parent to offspring; environment also influences traits.

Heredity

Transmission of traits from parents to offspring through genes.

Environment

All external factors that influence how traits develop in an individual.

Gene

A hereditary unit that controls a particular characteristic (Mendel's factors), e.g., eye color.

Chromosome

A long, coiled DNA-protein structure that contains thousands of genes.

DNA

Deoxyribonucleic acid; the molecule carrying genetic information, shaped as a double helix with a sugar-phosphate backbone and bases A, T, C, G.

Nucleotide

The basic unit of DNA, consisting of a sugar (deoxyribose), a phosphate, and a base (A, T, C, or G).

Base pairing

Rule that A pairs with T and C pairs with G (complementary base pairs).

Double helix

Two DNA strands twisted into a spiral, forming the shape of DNA.

Complementary base pair

A-T or C-G pairings in DNA.

Replication

Process of copying DNA before cell division; strands unzip and new complementary strands are formed.

Diploid

A cell with paired homologous chromosomes (2n).

Haploid

A cell with half the chromosome number (n), as in gametes.

Homologous chromosomes

Pairs of chromosomes that carry the same genes in the same order.

Allele

Different forms of the same gene (e.g., G or g).

Genotype

The genetic makeup of an individual (e.g., GG, Gg, gg).

Phenotype

The observable traits resulting from the genotype.

Homozygous

Having two identical alleles for a gene (GG or gg).

Heterozygous

Having two different alleles for a gene (Gg).

Dominant allele

An allele that masks the effect of a recessive allele in a heterozygote.

Recessive allele

An allele whose effect is masked in a heterozygote and may appear in homozygous form.

Monohybrid cross

A cross examining inheritance of a single trait.

Dihybrid cross

A cross examining inheritance of two traits.

Complete dominance

In a heterozygote, the dominant phenotype is expressed; the recessive is hidden.

Codominance

Heterozygote expresses both homozygous phenotypes distinctly.

Incomplete dominance

Heterozygote phenotype is a blend of the two homozygotes.

Punnett square

A diagram showing possible offspring genotypes from parental gametes.

True-breeding

Organisms that consistently produce offspring identical to the parent for a trait (homozygous).

Hybrid

Offspring with two different alleles for a trait (heterozygous).

Mendel

Father of Genetics; Austrian monk who studied peas and proposed basic inheritance patterns.

Pedigree

A chart showing family history of traits across generations.

Sex determination

Mechanism by which sex is determined; in humans, 23 pairs of chromosomes with XX female and XY male.

Autosomes

The 22 pairs of non-sex chromosomes.

Sex chromosome

The 1 pair of chromosomes that determine sex (X and Y).

X-linked inheritance

Inheritance of genes on the X chromosome; many recessive disorders; more common in males.

Carrier

An individual (often female) with a recessive disease allele who is phenotypically normal but can pass it to offspring.

Hemophilia

An X-linked recessive disorder affecting blood clotting.

Mutation

A change in the DNA sequence or chromosome that can alter a trait.

Mutagen

An agent that causes mutations (e.g., benzene, X-rays, gamma rays, UV light).

Silent mutation

A DNA change that does not alter the amino acid sequence of a protein.

Missense mutation

A DNA change that alters one amino acid in a protein.

Nonsense mutation

A DNA change that creates a premature stop codon.

Frameshift mutation

Insertion or deletion of nucleotides that shifts the reading frame of the genetic code.

Sickle-cell anemia

A disease caused by a single gene mutation.

Down syndrome

A chromosomal mutation (trisomy 21) with an extra chromosome 21.

Fossil

Preserved evidence of ancient organisms in rocks or soils.

Original fossil

Part of the organism preserved with the same chemical composition as when living.

Replacement fossil

Part of the organism replaced by minerals.

Carbon film fossil

A fossil formed when a thin film of carbon remains.

Relative dating

Dating by layering; older fossils are deeper; index fossils and fluorine analysis are used.

Absolute dating

Dating methods that give the actual age, e.g., radiometric dating and tree rings.

Darwin

Naturalist who proposed natural selection and common descent as the mechanism of evolution.

Natural selection

Process by which advantageous traits increase in frequency, leading to adaptation.

Speciation

Formation of new species from a common ancestor.

Geographic isolation

Physical barriers that separate populations, leading to divergent evolution.

Reproductive isolation

Barriers that prevent interbreeding between populations.

Homologous structures

Similar anatomical structures in different species due to a common ancestor.

Divergent evolution

Evolution of related species into different forms.

Convergent evolution

Unrelated species evolve similar traits due to similar environments.

Parallel evolution

Related species evolve similar traits independently due to similar pressures.

Fossil record

Evidence of past life preserved in rocks through fossils.

Human Genome Project

International effort to map the human genome; completed the mapping stage in 2003; produced a genetic map.

Genetic map

A map showing the positions of genes on chromosomes.

Selective breeding

Breeding plants and animals for specific desirable traits.

Genetic engineering

Techniques that alter DNA to change genes within an organism.

Genetically modified organism (GMO)

Organisms with altered gene sequences.

Gene therapy

Removing, altering, or inserting genetic material into a person’s cells to treat disease.