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As92022 L1 variation
ppt 2 sources of variation
| Question | Answer |
|---|---|
| Variation | Any difference between individuals of the same species. resulting from genetic, environmental, or combined influences. |
| Genetic variation | The range of different alleles; allele combinations in a species or population. |
| Gene pool | Sum of all alleles in a population |
| Population | All members of a species in a defined area, at a specific point in time. |
| Environment | All the abiotic and biotic factors an organism interacts with |
| Abiotic | All the interactions an organism has with non-living things, e.g., light, temperature, nutrients etc. |
| biotic | All the interactions an organism has with living things e.g., competition, predator/prey, parasites etc |
| Haploid (n) | one complete set of chromosomes (n=23 in humans), e.g. sperm, egg/ova, pollen |
| Diploid (2n) | two complete sets of chromosomes (2n=46 in humans) e.g. rest of body (somatic) cells. |
| Meiosis | Cell division that creates 4 genetically unique haploid sex cells (gametes). |
| Crossing over | homologous pairs exchange alleles between maternal and paternal chromatids resulting in new allele combinations in the gametes |
| Independent assortment | Homologous pairs randomly line up either side of cell center, mixing maternal and paternal chromosomes, introducing variation into the gamete that eventually form |
| Segregation | Alleles for a gene separate independently into different gametes. Mixes maternal and paternal alleles creating further variation in the gametes. |
| somatic cell | all body cells except sex cells |
| gamete | haploid sex cells e.g. sperm/egg, pollen/ova |
| Gonads | Organ that produces the gametes e.g., testes, ovary (animals), anther, ovary (plants). |
| Ova | Biological word for egg |
| Centromere | Where sister chromatids of a chromosome join |
| Sister chromatids | After DNA replication, each chromosome is made of two copies joined together, each copy is a sister chromatid. |
| Locus (loci plural) | The location of a gene on a chromosome |
| Mutagen | An agent that can induce or increase the frequency of mutations e.g. UV, chemicals. |
| Mutation | A permanent random change in the DNA sequence of a gene. The only source of new alleles |
| somatic mutation | Mutation that occurs in body (somatic) cells and are therefore not inherited, so only affects the individual within its lifetime |
| gametic mutation | Mutation that occurs in the gamete, (sperm/egg). When fertilized the mutation/new allele is inherited by the offspring and present in every body cell. |
| non-heritable | Is acquired after fertilization and is only present in somatic/body cells so is not passed on to offspring. |
| issues associated with small populations | •Low genetic diversity •Lower resilience to changes in environment •Increase chance of inbreeding •More susceptible to genetic drift |
| Inbreeding | When closely related individuals reproduce, increased chance of having the same harmful recessive alleles. Reduces fertility and genetic variation |
| relatedness | the proportion of an organism's genes that are shared with another individual due to common ancestry. The more closely related the more alleles are shared. E.g. Parent to offspring 50%, siblings 50% |
| fitness | a measure of an organism's ability to survive, reproduce, and pass on its genes to the next generation |
| genetic drift | change in allele frequency due to chance. Alleles maybe lost and/or fixed by chance. |
| inbreeding depression | The negative reproductive consequences for a population associated with having a high frequency of homozygous individuals possessing harmful recessive alleles. |
| non-random mating | animals choose their mates. Linked to inbreeding. Increase homozygous genotypes and reduces genetic variation |
| Human controlled non-random mating: strategic mating | human choose who mates, can choose individuals that have rare alleles/allele combinations and increase genetic variation, remove harmful alleles |
| migration (gene flow) | Movement of alleles between populations. |
| immigration | movement of alleles into a population: increases genetic variation by introducing new alleles or increasing the frequency of alleles |
| emigration | movement of alleles out of a population: decreases genetic variation by removing alleles or decreasing the frequency of alleles |
| translocation | A human controlled form of migration |
| natural selection | phenotypes best suited to the environment survive and have greater reproductive success, passing the "successful" alleles on to their offspring |
| selection pressure | Any factor that affects an organism survival and reproductive success. |
| fixed allele | Only one version of the gene remains in the gene pool e.g., brown eyes only e.g. bb |
Created by:
NZARoberts