Definitions Flashcards
DNA
The molecule that carries genetic instructions
Chromosome
Threadlike genetic structures that contain long lengths of DNA that holds many genes
Gene
Section of a chromosome that codes for one trait
Gamete
A sex cell
Allele
The different forms of a gene
Fertilisation
The fusion of 2 gametes
Zygote
A fertilised egg cell
Embryo
A ball of cells formed from the zygote by cell division
Foetus
An unborn or unhatched offspring that has developed beyond an embryo
Meiosis
The type of cell division that gametes are made by
Mitosis
The type of cell division body cells are made by
Sexual Reproduction
Reproduction that involves 2 individuals contributing genetically to offspring
Asexual reproduction
Reproduction that involves one individual genetically contributing to offspring
Variation
The differences(in DNA) of individuals in a population/species
Genotype
The alleles an individual has for a trait
Phenotype
The physical expression of a gene
Dominant allele
The allele that is always expressed when present
Recessive allele
The allele that is only expressed in the homozygous condition
Homozygous
Genotype with two of the same alleles
Heterozygous
Genotype with one dominant and one recessive allele
Punnett square
A diagram used to determine the probable outcomes of genetic cross between two individuals
Pure Breeding
An organism that is homozygous for a trait
Natural selection
The process whereby organisms better adapted to their environment tend to survive and produce more offspring
Mutation
A change in the base sequence of DNA
