Genetic Variation Definition Flashcards
Allele Frequency
How often different alleles for a particular gene occur in a population
Co-dominance
Where multiple alleles are expressed in the heterozygous phenotype
Crossing Over
Where sections of chromosomes are exchanged during meiosis to produce new combinations of alleles
Diploid Cells
Cells with a full set of chromosomes eg somatic cells
Gametes
Haploid cells produced by meiosis
Genetic Drift
Random changes in allele frequencies of a population due to chance
Haploid
A cell with half the number of chromosomes it should have eg gametes
Homologous Chromosomes
Chromosomes with the same genes in the same location but usually with different alleles, eg maternal and paternal chromosomes
Incomplete Dominance
Neither allele is completely dominant so the heterozygous phenotype is a blend of the two alleles
Independent Assortment
When homologous chromosomes line up during meiosis, they do so randomly, to make the combinations of chromosomes in the gametes totally random
Linked Genes
Genes that are close by on the same chromosomes and will be inherited together, aka are not separated during crossing over
Meiosis
Cell division to produce 4 different haploid gametes
Migration
The movement of alleles from one population to another
Multiple Alleles
Where some traits have more than two possible alleles
Natural Selection
Individuals with advantageous traits are more likely to survive to reproductive age, and pass on those beneficial traits
Segregation
Each parent’s chromatids split up randomly in the final meiosis division, so each gamete only has one random allele for each gene
Test Cross
Crossing an individual with an unknown genotype with a homozygous recessive individual and analysing the phenotype ratios of the offspring
Population bottleneck
An event occurs which drastically reduces population size by killing lots of individuals off - reduces genetic variation by killing off rare alleles
Founder effect
Where a small proportion of a larger original population migrates to a new location - the small population won’t have the same allele frequencies as the larger population, rare alleles likely won’t be seen in the small population
