Gene Pools Flashcards
Species
Organisms that can produce fertile offspring under natural conditions
Where does variation come from?
- Random assortment
- Crossing over
- Non-Disjunction
- Random Fertilisation
5 Mutations
Random Assortment
Chromosomes sorted into daughter cells randomly - many possible combinations of chromosomes from mother and father
Crossing over
Homologous chromosomes pair with eachother + exchange different segments
Non Disjunction
Chromosome pair fail to separate resulting in more/less number of chromosomes
Random Fertilisation
Chance alone responsible for which sperm meets which egg
Mutations
Pernament changes in DNA of chromosomes
Population
Group of organisms of same species living together in particular place + time
Gene Pool
Sum of all alleles in given population - can change.
Allele
Options for genes
Allele Frequencies
Usually measured in percentages
Natural Selection
Variation in population. Selection pressures makes traits favourable for survival. thoes traits survive + reproduce.
Speciation
- Variation - present in individuals
- Isolation - of gene pools + barriers of gene flow
- Struggle - Individual that possess suitable genes
- Selection - Suitable genes passed to offspring, unsuitable die
- Speciation - No longer reproduce with others/new species
Changes to allele frequencies
- Mutations - sudden + pernament changes to dna
- natural selection
- Random genetic drift - by chance allele frequency changes random + not associated to increase survival
- Migration - Gene flow from one population to another. individuals join, freq. change
- Barriers to gene flow - stop interbreeding + geographical + sociocultural
- Genetic diseases - fatal allele decrease in population over time
Bottleneck effect
Occurs after disaster reduces population to small handful - rarely represents actual genetic makeup of initial population
Founder Effect
Small group moves from original population to begin new poplatuon. Allele frequency from imigrating group different from frequencies of original population - can lead to random genetic drift
Genetic disease
Change allele frequencies in population. Epected frequ. for fatal allel will dec over time
Tay-Sachs Disease
Recessive autosomal. Homozygotes lack enzyme + accumulate lipids in nervous system. - inability to digest fats. results in mental/physical disabillities
Sickle Cell anaemia
Recessive. Caues flattening of erythrocytes - prevents carrying oxygen. High frequ in black populations
Thalassemia
Recessive disease that defects formation of haemoglobin + reduction in shape of RBC. high along mediterranean coast. Resistant to malaria
Alpha + Beta thalassemia similarities
Mutation for gene responsible for RBC/haemoglobin production.
Heterozygotes midly affected
heterozygotes carrier parents pass traits to children
recessive
Alpha nad Beta Thalassemia differences
Alpha - chromosome 16 (alpha globin)
Beta - chromosome 11 (beta globin)
Homozygous conditions in alpha = fatal
Homozygous conditions in beta = severe not fatal
No homozygote alpha sufferers but some beta
Fossils
Any preserved remains, imprint or trace left of a previously living organisms.
Fossils examples
Bones, teeth, footprints, faeces, burrows, egg shells
Artefact
Any object made by a human - not fossil
Fossils evidence +examples do…?
Provide evolution of which organisms lived on earth, provides examples of extinct organisms + transitional organisms between species.
Fossil Record
Sedimentary rock layers arranged in order they were deposited, most recent = top, oldest = bottom.
