Genetic Variation (Ncea Lvl 2)

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Alleles

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Variants of a gene

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Chiasma

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The point at which paired chromosomes contact during crossing over

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Co-Dominance

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An individual who is heterozygous will show both traits (yellow+red) in their phenotype

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Diploid

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Cell containing two complete sets of chromosomes, one from each parent.

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Evolution

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A gradual process in which organisms changes, usually becoming better and more complex

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Founder effect

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The reduced genetic diversity that results when a population is descended from a small number of colonising ancestors.

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Gamete

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Reproductive cell having the haploid no. of chromosomes

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Gene

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Sequence of DNA the occupies a specific location on a chromosome and determines a particular characteristic

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Genetic Biodiversity

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The total number of genetic characteristics in the genetic make-up of a species

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Gene Pool

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Total sum of different alleles in an interbreeding population

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Genetic Drift

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Process of change in the genetic composition of a population due to chance or random events rather than natural selection

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Genetic Variation

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Variation in the allele frequency or genome between members of species or groups of species

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Genotype

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Set of alleles that determines the expression of a particular characteristic or trait

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Haploid

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A cell that contains a single set of unpaired chromosomes.

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Heterozygous

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An individual with two different alleles for a specific trait

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Incomplete Dominance

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A relationship between alleles of a single gene, in which one allele masks the phenotypic expression of another allele at the same gene locus (red+ white = pink)

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Independant assortment

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Process of random segregation and assortment of chromosomes during meiosis resulting in the production of genetically unique gametes

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Lethal Alleles

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Alleles that cause an organism to die when present in homozygous condition

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Linked Genes

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Genes that are inherited together with other genes as they are located togeher on the same chromosome

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Locus

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The position that a given gene occupies on a chromosome

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Meiosis

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The process of cell division in sexually reproducing organisms that reduced the no. of chromosomes in reproductive cells from diploid to haploid

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Mutagen

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An agent (like chemicals, radiation) the cam induce or increase the frequency of mutation in an organism

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Mutation

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A permanent change to the base sequence of DNA

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Natural Selection

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The process whereby organisms better adapted to their enviroment tend to survive and produce more offspring

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Phenotype

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The set of observable characteristics of an individual resulting from the interaction of its genotype and the enviroment

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Population Bottleneck

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A sharp reduction of a populatipn due to enviromental events or human activites

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Segregation

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The separation of paired alleles or homologous chromosomes, especially during meiosis, so that the members of each pair appears in different gametes

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Somatic Cell

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Any cell of the body that is not a sexually reproductive cell

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Trait

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A genetically determined characteristic or condition

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Test Cross

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Cross between unknown genotype and homozygous recessive to identify unknown