Science - Genetic Variation: key terms Flashcards
Define: DNA
The molecule that carries the genetic instructions. shape; a double helix
Define: Gene
Section of a chromosome that codes for one trait
e.g. eye colour
Define: Allele
The different forms of a gene
e.g. brown eyes
Define: Chromosomes
Thread like structures found in the nucleus that contain long lengths of DNA that holds many genes.
Define: Fertilisation
The random fusing/joining of the male and female gametes to produce genetically unique offspring
Define: Base sequence
The order of bases (A, T, C and G) that form the genetic code
Define: Phenotype
Physical expression (appearance) of the gene/genotype
Define: Genotype
The alleles present (an individual carries) for a gene/characteristic/trait
Define: Sexual Reproduction
The combining/mixing DNA from two parents (through fertilisation using gametes produced by meiosis) to produce genetically unique offspring
THROUGH SEX!!! ;)))
Define: Meiosis
a cell division process that produces four genetically unique gametes with half the number of chromosomes as the parent cell.
Define: Crossing Over
During meiosis when DNA is exchanged between homologous chromosomes. This results in new allele combinations and therefore increases genetic variety.
Define: Independent assortment
When the homologous pairs line up during meiosis, the arrangement is random. Therefore, alleles will be put together in new combinations in gametes giving more genetic variety.
Define: Inheritable Variation
Involves a change in the DNA of gametes so can be passed on to offspring
Define: Non-inheritable variation
Is a change in the somatic cells so only affects the organism and cannot be passed onto offspring
Define: Homologous Chromosomes
Carry the same genes and one chromosome comes from the mother and one comes from the father.
Define: Pure Breeding
Homozygous for a trait (AA or aa)
Define: Genetic variation
Differences in the DNA/genes/characteristics of individuals in a species
Define: Recessive
The trait will only be expressed if two alleles are present in the genotype (aa)
Define: Dominant
The trait is always expressed if the allele is present in the genotype
Define: Mutation
A change in DNA (genetic material)
Define: Gamete
Sex cell with half the number of chromosomes (used for fertilisation in sexual reproduction) as the parent cell
VARPA
- Variation = exits in pop. random mutation
- Adaptation = survival advantages
- Reproduction = favorable adaptations –> reproduce
- Passing on = Fav. alleles passed on to OS
- Allele frequency = Fav. adapt. = common
