Genetic variation and Inheritance

Genetic variation

Differences in genetic information or alleles between individuals in a population. It can arise through mutation and through the creation of new combinations of alleles during sexual reproduction.

Mutation

A permanent change in the DNA sequence. A mutation can create a new allele and therefore introduce new genetic variation into a population.

Gametic mutation

A mutation that occurs in a gamete (sperm or egg) or in the cells that produce gametes. Because sperm and eggs contribute DNA to offspring, a mutation in this reproductive cell line can be passed to the next generation.

Somatic mutation

A mutation that occurs in a body cell other than a sperm or egg, such as a skin or muscle cell. Because these cells do not contribute their DNA to offspring, the mutation is generally not passed to the next generation.

Sexual reproduction

Reproduction involving genetic material from two parents. It creates genetically varied offspring because alleles from the two parents are combined in new ways.

Asexual Reproduction

A type of reproduction that involves a single parent and produces genetically identical offspring (clones) without the fusion of gametes or fertilisation.

Meiosis

A type of cell division that produces egg and sperm cells with half the number of chromosomes of the parent cell.

Crossing over

A process during meiosis where homologous pairs of chromosomes come together and exchange alleles between each other. This creates new and unique combinations of alleles in the resulting gametes.

Independent assortment

The random lining up of homologous chromosome pairs in the middle of a cell during meiosis, which creates unique combinations of alleles in gametes

Contributes to genetic variation by randomly mixing maternal and paternal chromosomes into gametes during meiosis.

Fertilisation

Fertilisation is the random fusion (joining) of a male gamete (sperm or pollen) and a female gamete (egg or ovule) to form a genetically unique single cell called a zygote

Zygote

A zygote is the very first single cell formed when a male sex cell (sperm) and a female sex cell (egg) fuse together during fertilisation

Pure breeding

An organism that is homozygous for a particular characteristic and consistently produces offspring showing the same characteristic when bred appropriately.

Indreeding

When closely related individuals reproduce, their offspring have a greater chance of inheriting the same allele from both parents, which can make harmful recessive characteristics more likely to appear.

Non-random mating / selective mating

When individuals in a population do not mate randomly and certain individuals are more likely to reproduce with particular individuals. This can affect which alleles are passed on within a population.

Gene pool

The complete collection of all the different alleles for all the genes found in a population. It represents the genetic variation available within that population.

Allele frequency

The proportion of copies of a particular allele within a population. Changes in allele frequency can indicate that the genetic makeup of a population is changing.

Natural selection

The process in which individuals with inherited characteristics that provide an advantage are more likely to survive and reproduce. As a result, the alleles associated with those characteristics can become more common in the population over generations.

Genetic drift

A random change in allele frequencies within a population. Its effects can be particularly noticeable in small populations because chance can have a larger influence on which individuals reproduce.