genetic variation

Gene

A sequence of bases (in DNA) that codes for a particular straight (eg.hair colour)

Allele

An alternative form of a gene (e.g blonde hair, brown hair, black hair)

Sexual reproduction

Involves in one gamete (sex cell) form each of two individuals combining to form a new individual. The new individual is therefore not identical to either parent.

Meiosis

Cell division to create four unique gametes, each with half a set of chromosomes.

Homologous chromosomes

Pairs of maternal and paternal chromosomes (same chromosomes but different alleles).

Soster chromatids

Identical copies of chromosomes made by DNA Replication

Crossing over

Sections of DNA are swapped between homologous chromosomes. This results in the chromosomes having new combinations of alleles > variation

Independent assortment

When homologous chromosomes line up at the cemtre of the cell, they do so independently of all of the other pairs. This means that it is random which combination of chromosomes ends up in which cell > variation

Segregation

The chromotids that the parent has are split up randomly, so that each gamete ends up a single allele for each trait. Which alleles it ends up with are down to chance > variation

Mutations

Changes in the base sequence of DNA

Co-dominance

A situation where two alleles are equally dominant so the physical expression of each allele can be seen in the individual.

Incomplete dominance

The inability for any allele to mask another allele. This results in a blended phenotype.

Multiple alleles

A gene which has more than two possible alleles.

Dihybrid inheritance

The simultaneous inheritance of alleles for two different genes. Punnet squares show dihybrid inheritance explore the liklihood of alleles on different genes being inherited together.

Linked genes

Genes which are highly likely to cross over together during meiosis

Genetic diversity

The differences in a population. The more genetically diverse it is, the greater amount of different alleles are present, and the more differences it has within it.

Natural selection

The tendency of individuals with more environmentally favorable alleles to survive. This maes them more likely to pa’s their alleles onto the next generation, resulting in a greater frequency of these alleles in tge gene pool.

Genetic drift

The changes in allele frequency within a gene pool between generations, which are completely due to chnace.

Gene pool

Total number of different alleles that exist within a population

Allele frequency

How often a certain allele occurs in the gene pool

Genetic change

Refers to the change in frequency of alleles in the gene pool of a population

Recombinant

The gametes produced as a result of crossing over

Inheritance

The passing on of genetic information from one generation to the next

Allele frequency

The number of times an allele is in a gene pool/population

Bottleneck

A sudden drastic reduction in population size due to an event, leading to loss of alleles in the gene pool

Genetic drift

A random even that changes allele frequency in the population