Genetic Variation

DNA

The molecule that carries genetic information. It is twisted into the shape of a double helix.

Chromosome

The structure formed when a DNA molecule coils around proteins. Each chromosome has a specific sequence of genes.

Gene

A section of DNA that codes for a particular protein.

Allele

An alternative form of a gene.

Nucleotide

The repeating unit of DNA; made up of a sugar, a phosphate and a base.

Phenotype

The observable characteristics an organism has due the interaction between its genotype and environment.

Genotype

The combination of alleles an organism has for a particular trait.

Variation

Differences between individuals of the same species.

Meiosis

A type of cell division that produces four genetically unique daughter cells called gametes.

Mutation

A permanent change in the base sequence of DNA. The ultimate source of genetic variation.

Crossing over

A process where sections of homologous chromosomes are exchanged during meiosis.

Independent assortment

A process where homologous chromosomes line up randomly on the equator of the cell, during meiosis.

Fertilisation

The fusion of a sperm with an egg.

Base pairing rule

A always bonds to T and G always bonds with C.

Gamete

A sex cell with one set of chromosomes

Homologous chromosomes

A pair of chromosomes that are the same size and contain the same sequence of genes. One is inherited from the mother, one is inherited from the father.

Trait

A feature of an organism.

Asexual reproduction

When genetically identical offspring are produced from a single parent.

Sexual reproduction

When genetically different offspring are produced by combining the genetic information from two parents.

Zygote

A fertilised egg.

DNA replication

A process where a molecule of DNA is copied before a cell divides.

Inheritable

Information that is passed on to offspring via the DNA of the gametes.

Non-inheritable

Information that can't be passed on to offspring.

Sister Chromatid

Identical copy (chromatid) formed by the DNA replication of a chromosome, with both chromatids joined together by a common centromere

Locus

The position of a gene on a particular chromosome is called the locus (plural = loci)