MODULE 6 Genetics, Evolution and Ecosystems
TOPIC 1 ○○ Repressor breaks away from operator Types of Gene Mutations ○○ RNA polymerase can bind to promoter •• Homeobox genes •• Types of gene mutations ○○ Regulate body part development ○○ Substitution ○○ Grouped in hox clusters –– Nucleotide replaced ○○ Precisely conserved due to importance ○○ Insertion ○○ Expressed anterior posterior –– Causes frameshift ○○ Determine where limbs branch off ○○ Deletion •• Apoptosis = programmed cell death in multicellular –– Causes frameshift organisms •• Consequences of gene mutations ○○ Enzymes break down cytoskeleton and DNA ○○ Neutral ○○ Remaining parts phagocytosed ○○ Harmful ○○ Controlled by complex cell signals ○○ Beneficial ○○ Causes limbs to separate •• Point mutation •• Transcription factors ○○ Only one base is affected ○○ Proteins/ noncoding RNA ○○ Silent mutation ○○ Attach/detach from DNA –– No change in amino acid sequence •• Introns = unexpressed DNA (don’t code for genes) ○○ Missense mutation • •• Exons = expressed DNA • Monohybrid = genetic diagram with just 1 gene –– 1 amino acid is changed in sequence •• Dihybrid = genetic diagram with 2 genes ○○ Excess amino acids deaminated in liver ○○ Nonsense mutation •• Linkage = when 2 or more gene loci are on the same ○○ Converted into ammonia then urea –– Triplet becomes stop codon chromosome ○○ Urea excreted in urine by kidney •• Gene expression regulation ○○ Autosomal linkage = when the two genes are on ○○ Some genes constantly expressed TOPIC 2 non-sex chromosomes ○○ Others expressed only when needed Patterns of Inheritence ○○ Sex linkage = when the two genes are on sex –– E.g. lac operon chromosomes –– Presence of lactose and absence of glucose •• Genotype = genetic makeup of an individual –– More likely to be on X chromosome triggers synthesis of enzymes that break down •• Phenotype = observd/ expressed characteristics of an •• Epistasis = interaction of non-linked genes where one lactose individual masks the other •• Lac operon = section of E.coli DNA ○○ Result of genotype and environment •• Recessive epistasis • ○○ Structural part codes for enzyme • Genetic factors contributing to phenotypic variation ○○ Homozygous recessive alleles mask expression of ○○ Operon part switches structural genes on/off ○○ Genetic random mutations another allele at different locus ○○ Promoter region = region where RNA polymerase –– Mutagenic agents ○○ E.g. flower colour in Salvia binds to begin transcription –– Chromosomal mutations •• Codominance = when two different alleles at the same •• Lac operon in absence of lactose –– Aneuploidy/ polyploidy locus are both expressed –– Variation from sexual reproduction ○○ Regulator gene expressed ○○ E.g. human blood group type •• Environmental factors contributing to phenotypic ○○ Repressor protein synthesised and binds operator •• Chi-squared test region variation ○○ Determine whether expected vs observed allele ○ Environment alone (e.g. limb loss in accident) ○○ RNA polymerase cannot bind promoter region ○ frequency differences are due to chance •• Lac operon in presence of lactose ○○ Environment affecting gene expression ○○ Use when... ○○ Epigenetics ○○ Lactose changes shape of repressor –– Data variation is discrete •• Genetic diagrams –– Large sample size
Super concise & exam board specific videos, notes & summaries by A* students at snaprevise.co.uk MODULE 6 Genetics, Evolution and Ecosystems
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Super concise & exam board specific videos, notes & summaries by A* students at snaprevise.co.uk MODULE 6 Genetics, Evolution and Ecosystems
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Super concise & exam board specific videos, notes & summaries by A* students at snaprevise.co.uk MODULE 6 Genetics, Evolution and Ecosystems
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Super concise & exam board specific videos, notes & summaries by A* students at snaprevise.co.uk MODULE 6 Genetics, Evolution and Ecosystems
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Super concise & exam board specific videos, notes & summaries by A* students at snaprevise.co.uk