NCEA Biology 2.5 - Sources of Genetic Variation Vocabulary

Vocabulary flashcards covering key terms, definitions, genetics concepts, and sources of variation based on the provided NCEA Biology 2.5 notes.

Allele

Any of two or more alternative variants or forms of a gene that occupy the same relative position (locus) on homologous chromosomes and are responsible for alternative characteristics.

Allele frequency

The percentage of a population of a species that carries a particular allele on a given chromosome.

Chiasma

The point at which paired chromosomes contact during crossing over.

Continuous variation

Variation within a population in which a graded series of intermediate phenotypes falls between two extremes, such as human height, body weight, and hand span.

Crossing over

A process occurring during meiosis wherein two chromosomes pair up and exchange segments of their genetic material.

Diploid

A cell that contains two complete sets of chromosomes ($2n$), one set from each parent (e.g., human somatic cells contain 46 chromosomes).

Discontinuous variation

Variation within a population in which characteristics fall into a number of distinct classes or categories with few or no intermediate phenotypes, such as human blood groups, ear lobe attachment, and tongue rolling ability.

Gamete

A reproductive cell having the haploid number of chromosomes, especially a mature sperm or egg.

Gene

A section or sequence of DNA that occupies a specific location on a chromosome and holds the instructions to code for one protein or trait.

Gene pool

The total sum of different alleles in an interbreeding population.

Genetic variation

Variation in the allele frequency or genome between members of a species, or between groups of species.

Haploid

A cell that contains a single set of unpaired chromosomes (e.g., human gametes containing 23 unpaired chromosomes).

Heritable

Capable of being passed from one generation to the next.

Independent assortment

The process of random segregation and assortment of chromosomes during meiosis resulting in the production of genetically unique gametes.

Locus

The specific position or location that a given gene occupies on a chromosome.

Meiosis

The process of cell division in sexually reproducing organisms that reduces the number of chromosomes in reproductive cells from diploid to haploid.

Mutagen

An agent, such as a chemical, ultraviolet light, or a radioactive element, that can induce or increase the frequency of mutation in an organism.

Mutation

A permanent change in the base sequence of DNA, which acts as the source of variation that can produce new alleles.

Trait

A genetically determined characteristic or condition, such as eye colour.

Segregation

The separation of paired alleles or homologous chromosomes, especially during meiosis, so that the members of each pair appear in different gametes.

Somatic cell

Any cell of the body that is not a sexually reproductive cell (e.g., a gamete).

Chromatin

Substance made up of DNA tightly bound to proteins called histones.

Histones

Proteins around which DNA is tightly wound to form chromatin.

Centromere

The structure that joins two sister chromatids together in a replicated chromosome.

Homologous chromosomes

Paired chromosomes (homologues) that carry the same genes in the same location (locus) as one another, with one set inherited from the mother and one set from the father.

Species

A category used by scientists to classify organisms of the same type that are able to reproduce to make more of that species, such as Homo sapiens.

Phenotype

The physical appearance or expressed characteristics of an individual, produced by the interaction of its genotype with the environment ($\text{Genotype} + \text{Environment} = \text{Phenotype}$).

Genotype

The unique combination of alleles possessed by an individual organism.