U2T6 - Keywords Flashcards
Population Genetics
Population
All of the organisms of one species, who live in the same place at the same time, and can breed together.
Gene Pool
Sum total of all genes + alleles in pop/species at particular time. Can vary from generation to generation due to variation + mutations.
Hardy Weinberg Principle/Equation
Frequency of dominant + recessive alleles in population remains constant from gen to gen, provided certain conditions exist.
Hardy-Weinberg Formula (A)
Allele Frequencies
p + q = 1
p = Frequency of dominant alleles
q = Frequency of recessive alleles
Hardy-Weinberg Formula (B)
Genotype Frequencies p2 + 2pq + q2 = 1 p2 = Frequency of homozygous dominant 2pq = Frequency of heterozygous q2 = Frequency of homozygous recessive
Allele Frequency
Proportion of particular allele in pop/species at particular time.
Genotype Frequency
Total num each genotype in given pop
Random Mating
Not choosing a mate, like plants. Animals don’t do this.
Shuffle Variation
Sources of variation that shuffle existing genetic info, don’t form new forms of alleles/genes. Mutation required for that.
Mutation
Permanent, spontaneous changes to the genetic makeup of alleles/num of chromosomes/DNA.
Gene Mutations
Occur when there are changes to letters making up triplet code. May be 1 base substitution or deletion or addition of new base. Changes can occur at base pair of DNA of gene. May be caused by chemical/radiation (x-ray). Restricted to 1 gene.
Gene Mutation Substitutions (Sickle Cell Anaemia)
Gene for B-Haemoglobin on chromosome 11 prone to single gene mutation + protein synthesis error. Thymine substituted by adenine so CTT becomes CAT. Causes Valine to replace Glutamate so abnormal haemoglobin forms into long fibres that distort RBCs into sickle shapes.
Gene Mutation Deletions
Occurs when 1+ nucleotides not copies during DNA replication. Can result in non functional proteins as it shifts ribosome’s reading frame. AA’s coded for after deletion may be totally different to OG DNA molecule.
Chromosome Mutations
Occur when large bits/entire/sets of chromosomes fail to segregates. E.g. Down’s Syndrome.
Down’s Syndrome
Chromosome 21 doesn’t segregate during meiosis. Egg cell contains 2 copies of chromosome 21 so upon fertilisation, zygote contains 3 copies of chromosome 21, leading is trisomy 21.
Trisomy 21
Three copies of chromosome 21 in a zygote.
Selection
Editing of genetically inheritable features in pop, increases frequency of some while decreasing frequency of others.
Natural Selection
Presence of variation in pop allows diff members to be more suited to current environmental conditions than others (obtain + use resources, mate, evade predators, catch prey). Impact survival. Most able to survive = fittest. Over time, adaptations of fitter controlled by alleles, favoured + so increase in the allele frequencies so more of the favourable phenotype.Better adapted organisms more likely to survive + produce more offspring. Brings about evolution.
Directional Selection
Selection of organisms whose phenotype, at 1 end of variation range gives selective advantage. In normal distribution curve, phenotype shifts to left or right (moves moda, value). Most likely when environment changes or pop colonises new habitat. New code = new optimism value.
Mode
Most common number/phenotype.
Stabilising Selection
Form of selection that selects against both extremes + favours individuals with average phenotypes. If extremes found, they’re selected against. Common in stable ecosystems. No obvious phenotype change, doesn’t drive evolutionary change. E.g. birth mass in humans (high + low birth weights less likely to survive)
Polymorphism
Diff forms of organism’s traits that can be found (blood groups, eye colour). Can investigate forms of selection (sickle cell in Central Africa as results in malarial parasite less able to complete life cycle so confers malarial resistance)
Species
Group of individuals of common ancestry that closely resemble each other + normally capable of interbreeding to produce fertile offspring.
Speciation
Formation of new species from existing species that are reproductively isolated from other species.
Evolution
Formation of new species from existing species.
Aneuploidy
Having abnormal num of chromosomes in haploid set.
Polyploidy
Having 2+ paired (homologous) sets of chromosomes.
Polymorphic Population
Occurrence of 2+ diff forms/phenotypes in pop of species.
Sympatric Speciation
Speciation that occurs when 2 groups of same species live in same place, but evolve differently until they can’t interbreed + are diff species.
Interspecific Competition
Competition between diff pops for resources.
Selection Pressure
Agent of diff mortality/fertility that tends to make pop change genetically.
Niche
Role taken by type of organism within community.
Hybridisation
Process of animal/plant breeding with individual of another species/variety.
Habitat Isolation
Populations inhabit different local habitats within one environment.
Temporal Isolation
Pops use same environment but are reproductively active at diff times.
Genome
All DNA in individual.
Point Mutations
Genetic Mutations which affect only 1 base. Can involve substitution/deletion of single bases. Relatively common.
Frameshift Mutations
When 1 base removed from DNA sequence. Changes entire section of DNA. All amino acids after mutation point may be changed or shortened if stop codon produced earlier than intended.
Sub-Species
Separate populations that haven’t diverged enough to produce separate species but may in future. Differ in several signif aspects but can still interbreed + produce fertile young.
