Genetic Variation Terms

DNA

molecule containing the genetic information that makes up the chromosomes.

Chromosome

tightly coiled DNA located within the nucleus

Gene

A section of DNA that codes for a specific trait

Allele

An alternative form of a gene.

Homologous

A pair of chromosomes carrying the same sequence of genes

Nucleus

A part of the cell containing DNA

Genotype

combination of alleles for a gene

Phenotype

observable characteristics determined by your genotype

Heterozygous

An organism that has two different alleles for a gene. Eg Bb

Homozygous

An organism that has two identical alleles for a gene. Eg BB or bb

Dominant

An allele that is always expressed in the phenotype

Recessive

An allele that is not expressed unless two copies are present in the genotype

Pure bred

An organism that is homozygous for a trait

test cross

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

Diploid

containing two complete sets of chromosomes

Haploid

having a single set of unpaired chromosomes

Fertilisation

Fusing of a male gamete with a female gamete.

Genetic Variation

Differences in DNA within a species

Meiosis

a type of cell division that creates gametes

Mutation

permanent change in the DNA base sequence

Natural Selection

A process where individuals who are best suited to their environment are more likely to survive and reproduce, passing on their favourable alleles.

Pure Breeding

Individuals that are homozygous that will always produce the same offspring when crossed together

semi conservative

in each new DNA double helix, one strand is from the original molecule and one strand is new

Somatic Cell

body cell

Gametic Cell

Sex cell, such as sperm or egg.

Mitosis

a type of cell division that results in two identical cells for growth and repair

Nucleotide

A building block of DNA, consisting of a base, sugar and phosphate

Zygote

fertilized egg

Carrier

A person who is heterozygous for a recessive disorder

asexual reproduction

A reproductive process that involves only one parent and produces offspring that are identical to the parent.

sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which genetically differs from both parents