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Genetic variation (Genetic change (Genetic biodiversity (Measure of the…
Genetic variation
Genetic change
Genetic biodiversity
Measure of the different genetic combinations within a gene pool. The amount of genetic diversity in a population may affect the likelihood
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Genetic drift
Frequency of alleles changing, due to a chance event, rather than a selection pressure e.g. being alike to your mother more than your father
Founder effect
Small number of individual emigrate from a population or become geographically isolated from their original population. The new population may have reduced frequency and range of alleles, and have less genetic variation between them.
Bottleneck affect
Population numbers can be reduced by human/environment. A large section of the population is killed off, and the remaining population are unlikely to represent the orgininal frequency, Increased interbreeding will occur between close relatives ----genetic diversity will reduce----may hinder the surviving populations ability to survive in the future
Geneflow
Migrating individuals interbreed within new populations, contributes to gene pool of local population, distribution of favourable mutations, reduced genetic variation between the populations
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Evolution
Change in characteristics of living things over a long period of time, natural selection- living things with beneficial traits produce more offspring than others, resulting in a change of traits overtime.
Predicting inheritance
Monohybrid Cross
A monohybrid cross is a mating between two organisms with different variations at one genetic chromosome of interest. The characters being studied in a monohybrid cross are governed by two or multiple variations for a single locus.
Test cross
Mateing a organism in question of being a pure bred with an individual that is homozygous reccesive for that trait
Co-dominance
This is a single gene that has more than one dominant allele. an individual that is hetrozygus with two co-dominant alleles will show the phenotype of both alleles. for example a hetrozygus flower with co-dominant alleles of red and white would have some red petals and some white in its phenotype.
Dihybrid cross
Dihybrid cross is a cross between two different lines/genes that differ in two observed traits. In the Mendelian sense, between the alleles of both these loci there is a relationship of complete dominance - recessive.
Incomplete Dominance
incomplet dominance is when an allele is not completly domanant so a hetrozygus individual will still show part of the reccesive gene in the phenotype the phenotypes will blend together for example if a flower has white alleles and red alleles a hetrozygus flower would be a blend of both the pink alleles and the white so it will be pink.
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Pure Breeding
individuals that are pure breeding have homozygous genotype for a certain trait that they are being breed for this is ether dominant or rescessive if these individuals are breed with another pure breeder for that trait they will only produce offspring with the same genotype as the parent
Lethal Alleles
alleles that produce a phenotypic trait that that causes death. arise due to a mutation in an essential gene. the mutation means the gene cannot produce a functioning version of a protein.
Sources of variation
Mutations
The permanent change to the base sequence of DNA, it is considered to be the ultimate source of variation as it creates new alleles within a population. For it to be inherited into offspring, the mutation must occur in the gametic cells, rather than the
Neutral- no observable effect to the organism, does not provide an advantage or disadvantage . Beneficial- survival advantage e.g. in conditions where others die. Harmful- may affect survival, or generation depending if it is located in the gamatic cells
Types of mutations
Deletion- part of the chromosome breaks off reducing its size and reducing the chromosomes and alleles on it
Inversion- rearrangement of genetic info on chromosome, does not affect overall length
Translocation- movement from 1 chromosome to another, affects overall length of chromosome
Duplication- genetic material is copied, duplication of genes and increases in length
Segregation
Pairs of alleles are segregated when homologous chromosomes split, so that each gamete receives one alleles for each pair- unique
Meiosis
Used to produce male and female gametes, contain haploid number of chromosomes as original, genes get shuffled and variation occurs
Crossing over
Homologous chromosomes swap parts (genes) of their chromosomes, breaking up the gene combinations and altering the genetypes and phenotypes of the organism
Independant assortment
Homologous pairs of chromosomes line up randomly at the cell equator during meiosis, and do so randomly. It means it is completely random which combination of alleles will end up in each of the four gametes produced