Stage 5 Science: Genetics & Evolutionary Change

Comprehensive vocabulary flashcards covering DNA structure, Mendelian genetics, reproduction, mutations, and natural selection based on the Stage 5 Science curriculum.

DNA (deoxyribonucleic acid)

The molecule that stores genetic information as a chemical code in the cells of every living organism, inherited and passed from parents to offspring.

Nucleotide

The building block of DNA, consisting of a phosphate, a sugar, and one of four nitrogenous bases ($A$, $T$, $G$, or $C$).

Double Helix

The ladder-shaped structure of DNA consisting of two long strands twisted around each other.

Base-pairing Rule

The specific pairing in DNA where Adenine ($A$) always pairs with Thymine ($T$) and Guanine ($G$) always pairs with Cytosine ($C$).

Gene

A section of DNA that acts as the basic functional unit of heredity, usually providing instructions to build a specific protein.

Chromosome

A long DNA molecule tightly coiled around histone proteins to fit inside the cell nucleus.

Genome

The complete sequence of all an organism's DNA, encompassing every chromosome and every gene.

DNA Replication

The process by which DNA unzips and matches new bases to existing strands to create two identical copies before a cell divides.

Chargaff’s Rules

The discovery from the 1940s that states that in DNA, the amount of Adenine ($A$) always equals Thymine ($T$), and Guanine ($G$) equals Cytosine ($C$).

Asexual Reproduction

A process by which a single organism creates a genetically identical copy (clone) of itself, such as through binary fission or budding.

Sexual Reproduction

A process requiring two parents and the fusion of gametes to create offspring with a unique genetic sequence.

Mitosis

A type of cell division for growth and repair that results in two identical diploid daughter cells with $46$ chromosomes in humans.

Meiosis

A type of cell division occurring in reproductive organs that produces four unique haploid gametes with $23$ chromosomes.

Allele

A specific variant or alternative form of a gene, such as attached versus free earlobes.

Genotype

The specific alleles an organism carries for a trait (e.g., $Bb$ or $bb$).

Phenotype

The observable physical or biochemical traits of an organism resulting from its genotype and environment.

Dominant Allele

An allele that hides the effect of a recessive allele and only requires one copy to be expressed in the phenotype.

Recessive Allele

An allele that is masked by a dominant one and requires two copies to be seen in the phenotype.

Homozygous

A genotype where an individual has two copies of the same allele (e.g., $AA$ or $aa$).

Heterozygous

A genotype where an individual has two different alleles for a gene (e.g., $Aa$).

Punnett Square

A grid tool used to predict the possible genotype and phenotype ratios of offspring from a specific genetic cross.

Pedigree

A family tree diagram used to track the inheritance of a single trait across multiple generations using standard symbols.

Mutation

A change in the sequence of bases in the DNA, which can be beneficial, harmful, or neutral.

Mutagen

A factor that increases the chance of DNA mutation, such as UV radiation, X-rays, or certain chemicals.

Natural Selection

The process by which individuals with advantageous traits better suited to their environment are more likely to survive and reproduce.

Selection Pressure

Factors like competition, predation, or ecosystem change that determine which traits provide a survival advantage.

Speciation

The formation of a new species that occurs when populations are isolated and diverge enough that they can no longer interbreed.

CRISPR Gene Editing

An emerging genetic technology that uses the $Cas9$ protein and guide RNA as "molecular scissors" to edit DNA at a precise location.

Selective Breeding

The traditional practice of choosing parents with useful traits over generations to achieve a desired outcome in offspring.

Genetic Rescue

A conservation application that involves adding new genetic variation to a small, inbred population to boost its survival and fitness.