GENETIC VARIATION AND CHANGE Flashcards
MEIOSIS
Cell division for the formation of gametes
SEGREGATION
When homologous pairs organise side by side during meiosis
INDEPENDENT ASSORTMENT
The random arrangement of homologous pairs of chromosomes during meiosis
CROSSING OVER
When homologous chromosomes pair up during meiosis
COMPLETE DOMINANCE
One allele completely masks the expression of another allele. A heterozygous individual will show the phentoype of the dominant allele
INCOMPLETE DOMINANCE
When alleles do not show complete dominance over each so that heterozygous genotypes produce phenotypes which display a mixture of each form of the trait
CODOMINANCE
When a gene has more than one dominant allele, so that in heterozygous individuals both forms are expressed equally in the phenotype
MULTIPLE ALLELES
When there are more than 2 alleles for a characteristic
LETHAL ALLELE
Lethal alleles are those that cause the death of the organism, and are usually the result of a mutation
TEST CROSS
When an individual displaying the dominant trait is crossed with a homozygous recessive individual in order to determine its genotype
LINKED GENES
Whem genes for different chracteristics are found on the same chromosome and are therefore distributed together during meiosis
GENE POOL
The collective number, type and variety of all the genes present in a population
GENETIC VARIATION/ BIODIVERSITY
A measure of the different genetic combinations in a gene pool
MIGRATION
The movement of individuals from one population to another (or to create a new population)
GENE FLOW
The exchange of genes/ alleles between populations due to migration
NATURAL SELECTION
The process where alleles which produce environmentally favourable phenotypes have a higher probability of being inherited than other alleles
SELECTION PRESSURE
An environmental factor hich causes some phenotypes to be more favourbale for survival than others
GENETIC DRIFT
The random change in allele frequencies in a gene pool, which is generally accelerated in smaller populations
MUTAGEN
A factor which increases the likelihood of a mutation occurring
SOMATIC MUTATION
A mutation which occurs in a normal body cell and is not inherited
GAMETIC MUTATION
A mutation which occurs in a gamete and is possibly inherited
BOTTLENECK EFFECT
The change in genetic variation in a population as a result of mass death of the majority of individuals
FOUNDERS EFFECT
The change in genetic variation in a small population which has migrated from a larger parent population
DIHYBRID CROSS
A genetic cross determining the likelihood of inheritance for two traits which independently assort
