DNA, Genetics & Evolution – Lecture Review

Traditional vocabulary flashcards summarizing key terms and definitions from the lecture on DNA, genetics, inheritance and evolution.

Genetics

The study of heredity, examining how characteristics are passed from parents to offspring.

Environment (in heredity)

The set of external factors that also influence an individual’s characteristics alongside genetic factors.

Gene

A hereditary unit (Mendel’s ‘factor’) that controls a specific characteristic, such as eye colour.

Chromosome

A long, coiled thread-like structure composed of DNA and protein that contains thousands of genes.

DNA (Deoxyribonucleic Acid)

The molecule that carries genetic information; made of two antiparallel strands forming a double helix.

Double Helix

The twisted-ladder shape formed by the two strands of the DNA molecule.

Watson and Crick

Scientists who uncovered the correct structure of DNA in 1953.

Nucleotide

The building block of DNA, consisting of a phosphate group, deoxyribose sugar and a nitrogen base.

Complementary Base Pairing

Specific pairing in DNA where adenine bonds with thymine and cytosine bonds with guanine.

DNA Replication

The process of making an exact copy of DNA before cell division; strands unzip and pair with complementary bases.

Diploid Cell

A cell containing two sets of chromosomes (2n); e.g., 46 in humans.

Haploid Cell

A cell containing one set of chromosomes (n); e.g., 23 in human gametes.

Homologous Chromosomes

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

Gamete

A reproductive cell (sperm or egg) that carries a haploid set of chromosomes.

Fertilization

The fusion of male and female gametes to form a diploid zygote.

Mitosis

Cell division producing two genetically identical daughter cells for growth and repair in somatic tissues.

Meiosis

Cell division in reproductive organs producing four genetically different haploid gametes.

Allele

Different versions of the same gene, such as G and g for pod colour.

Homozygous

Having two identical alleles for a trait (e.g., AA or aa).

Heterozygous

Having two different alleles for a trait (e.g., Aa).

Dominant Trait

A characteristic expressed in the F1 generation that masks the recessive allele when heterozygous.

Recessive Trait

A characteristic masked in the F1 generation but reappearing in F2 when homozygous.

Phenotype

The observable physical or biochemical characteristics of an organism.

Genotype

The genetic makeup (allele combination) of an organism.

Punnett Square

A grid system used to predict the genetic outcomes of a cross.

Complete Dominance

Inheritance where the dominant allele completely masks the recessive allele in heterozygotes.

Codominance

Inheritance where both alleles in a heterozygote are fully and independently expressed.

Incomplete Dominance

Inheritance where the heterozygote phenotype is a blend of the two homozygotes.

Autosomes

The 22 pairs of non-sex chromosomes in humans.

Sex Chromosomes

The pair of chromosomes (XX or XY) that determine biological sex in humans.

Pedigree Chart

A diagram that shows family relationships and the inheritance of traits across generations.

Sex-Linked (X-Linked) Inheritance

Inheritance of genes located on the X chromosome; traits are often more common in males.

Carrier (Genetics)

A heterozygous female who carries a recessive X-linked allele but does not express the trait.

Mutation

Any spontaneous change in a gene or chromosome that can alter a characteristic.

Mutagen

An agent that causes mutations, such as benzene, X-rays or UV light.

Sickle-Cell Anaemia

A genetic disorder caused by a single gene mutation affecting haemoglobin shape.

Down Syndrome (Trisomy 21)

A chromosomal mutation where an individual has an extra chromosome 21.

Human Genome Project

International effort completed in 2003 to map the entire human genetic code.

Selective Breeding

Breeding organisms to enhance desired traits through controlled mating.

Genetic Engineering

Direct manipulation of an organism’s DNA to alter its genes.

Genetically Modified Organism (GMO)

An organism whose genome has been altered via genetic engineering.

Gene / Stem-Cell Therapy

Treatment that involves modifying a patient’s genetic material and re-introducing it to treat disease.

Evolution

The process of change in living organisms over time from common ancestors.

Natural Selection

Mechanism of evolution where individuals with favorable traits survive and reproduce more successfully.

Speciation

The formation of new species through genetic divergence and reproductive isolation.

Fossil

Preserved evidence of past life found in rocks or soils.

Index Fossil

A widespread, short-lived species used to compare the relative ages of rock layers.

Relative Dating

Method of determining the age of fossils by comparing their placement in rock layers.

Absolute Dating

Dating technique giving a numerical age, often using radioactive decay (e.g., carbon dating).

Half-Life

The time required for half the atoms of a radioactive isotope to decay.

Homologous Structures

Body parts with similar fundamental structure owing to common ancestry (e.g., pentadactyl limb).

Analogous Structures

Body parts with similar function but different evolutionary origins, indicating convergent evolution.

Convergent Evolution

Independent evolution of similar features in unrelated groups (e.g., shark and dolphin body shape).

Divergent Evolution

Accumulation of differences from a common ancestor leading to new species.

Parallel Evolution

Related species evolving similar traits independently after separation.