Genetic Variation

• genetic variation describes naturally occurring genetic differences among individuals of the same species
• all organisms are slightly or greatly different
• variation permits flexibility and survival of a population in the face of changing environmental circumstances and can also produce variation in the gene pools
• variation is important
• genetic variation is a biological advantage as having individuals in a species all slightly different leads to the ability of some of these individuals being able to adapt and change to the changes that may occur within their environment - this leads to survival of these individuals
• allele - different forms of a gene due to slightly different order of bases eg. brown eyes, blue eyes
• allele frequency - is a measure of the relative frequency of an allele on a genetic locus in a population
• asexual reproduction - reproduction involving only one parent. dosent produce genetic variation
• chiasma - point of contact, the physical link, between 2 (non-sister) chromatids belonging to homologous chromosomes during crossing over
• co-dominance - heterozygous individuals have a phenotype that shows the phenotype of both parents
• complete dominance - a form of dominance in heterozygous conditions wherein the allele that is regarded as dominant completely masks the effect of the allele that is recessive
• crossing over - occurs during meiosis, when the homologous chromosomes line up at the equator, sometimes they tangle, swap and exchange genetic information
• diploid - a cell or an organism consisting of 2 sets of chromosomes: usually one set from the mother and another from the father
• evolution - is the change in the characteristics of a species over several generations and relies on the process of natural selection
• fertilization - a process in sexual reproduction that involves the union of male and female gametes to produce a diploid zygote
• Fi - the parental generation (P1) is the first set of parents crossed. The F1 (first filiai) generation consists of all the offspring from the parents
• founder effect - is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population
• gamete - sex cell of an organism eg. sperm, egg, pollen, ova
• gamete cells - sex cells with half the number of chromosomes. If a mutation occurs in one of these cells and that cell results in a zygote, all cells in the offspring will have the mutation
• gene - a length of dna that hold the instructions for a characteristic
• gene pool - refers to the total number of genes of every individual in a population
• genetic diversity - the total number of genetic characteristics in the genetic makeup of a species
• segregation - the process that occurs during meiosis where parts of alleles are separated when the homologous chromosomes split
• selective pressure - can take many forms, including environmental conditions, availability of food and energy sources, predators, diseases, and even direct human influence. the selective pressure means that animals that don't have these characteristics are less likely to survive and reproduce due to natural selection
• sexual reproduction - reproduction involving 2 parents, produces genetic variation
• somatic cells - body cells, if a mutation occurs in these calls it will not be passed on to offspring
• test cross - a genetic cross between a homozygous recessive individual and a corresponding suspected heterozygote to determine the genotype of the latter
• genetic drift - is the change in the frequency of an existing gene variant (allele) in a population due to random chance alone and not natural selection
• genotype - the genetic make up of the organism
• haploid - when a cell has half the usual number of chromosomes
• heterozygous - different forms of the allele are present in the genotype
• homologous chromosomes - chromosome pairs (one from each parent) that are similar in length, gene position, and centromere location they contain. the position of the genes may contain different alleles
• homozygous - the same form of the allele is present in the genotype
• incomplete dominance - heterozygous individuals have a phenotype that is intermediate between the 2 homozygous phenotypes (like a bland)
• independent assortment - the way the homologous chromosomes line up at the equator maternal and paternal, is completely random
• lethal genes - alleles that produce a gene product that kills the offspring
• linked genes - genes located on the same chromosome that tend to be inherited together
• meiosis - the type of cell division which produces gametes
• migration - movement of organisms into and out of a population
• multiple alleles - when 3 or more alternative forms of a gene that can occupy the same locus