Inheritance, Variation and Evolution - Paper 2

DNA (Deoxyribonucleic acid)

A polymer made up of two strands forming a double helix, which contains the genetic material of an organism.

Gene

A small section of DNA on a chromosome that codes for a particular sequence of amino acids, resulting in a specific protein.

Allele

Different versions of the same gene, which can be dominant or recessive.

Genotype

The collection of alleles that determine an organism's characteristics, often represented by symbols such as AA, Aa, or aa.

Phenotype

The observable physical characteristics of an organism, determined by its genotype and its interaction with the environment.

Homozygous

An organism that has two identical alleles for a particular gene (e.g., BB or bb).

Heterozygous

An organism that has two different alleles for a particular gene (e.g., Bb).

Variation

The differences in characteristics between individuals of the same species, which can be caused by genetic factors, environmental factors, or a combination of both.

Mutation

A random change in the DNA sequence that can lead to a new phenotype; most have no effect, but some can be beneficial or harmful.

Evolution

A change in the inherited characteristics of a population over time through a process of natural selection, which may result in the formation of new species.

Natural Selection

The process by which individuals with characteristics best suited to their environment are more likely to survive and reproduce, passing on their alleles.

Speciation

The formation of a new and distinct species in the course of evolution, often occurring when populations become isolated.

Extinction

The permanent loss of all members of a species from Earth.