4. genetic diversity and evolution

    Cards (26)

    • species- a group of similar organisms that can successfully breed together to produce fertile offspring
    • mutagenic agents- increases rate of mutation by physical/ chemical factors such as; ionising radiation or carcinogenic chemicals
    • substitution mutation
      • substitute replaces one base with another
      • number of bases stays the same
      • no frameshift
    • deletion/ insertion mutation
      •  takes away/ adds bases so number will decrease/ increase
      • frameshift occurs and different protein produced
    • how mutation leads to production of a non-functional enzyme
      • change in base sequence of DNA
      • causes change in amino acid sequence in
      • which changes hydrogen, ionic and disulphide bonds in 3°
      • which will change the active site of an enzymes
      • substrate no longer complimentary so no ES complexes form
    • how chromosomes produce genetic variation in gametes
      • crossing over of chromatids
      • independent segregation in second cell division
    • meiosis
      • 2 cell divisions, produce 4 non-identical daughter cells
      • variation caused by random assortment and crossing over of chromatids
      • crossing over occurs in first cell division
      • produces half the number of chromosomes
    • how meiosis produces haploid chromosomes and shows genetic variation
      • homologous chromosomes pair up
      • crossing over occurs producing new combination of alleles
      • chromosomes separate at random
      • producing a varying combination of chromosomes
      • chromatids separated at meiosis 2 (independent assortment)
    • crossing over occurs at the chiasma
    • how crossing over causes genetic variation (4)
      • homologous chromosomes from a bivalent
      • sister chromatids exchange alleles at chiasma
      • producing new combination of alleles
    • genetic diversity- number of different alleles of genes in a population
    • natural selection- process by which organisms better adapted to the environment survive and reproduce and pass on their advantageous alleles to their offsprings producing different phenotypes
    • variation- differences in the base sequence of DNA or amino acid sequence of proteins
    • variation
      • genetic: mutation, meiosis independent assortment or crossing over, fertilisation of gametes
      • environmental: climate change, availability of water/food, light intensity, water and nutrients in soil
    • genetic bottleneck- reduce number of different alleles, reduce genetic diversity. survivors produce larger populations but reduced diversity remains
    • founder effect- start a new colony due to geographical isolation
    • natural selection
      • (geographical isolation occurs therefore no interbreeding/ reproductive isolation)
      • there is variation in a population
      • due to mutation some have favourable alleles which allow them to survive and reproduce
      • pass on favourable alleles to offsprings, so frequency of alleles in population increase
    • stabilising selection (5)
      • occurs in unchanging environment
      • selection for the mean
      • range of standard deviation is reduced
      • increased proportion of population becomes well adapted to the environment
      • increasing allele frequency
    • directional selection
      • individuals with alleles for a single extreme phenotype are more likely to survive and reproduce
      • change due to environment increasing allele frequency
    • anatomical- internal or external physical feature
      -camouflage, mimicry
      -waxy cuticle, spines
    • behavioural- acts are inherited or learned through experience
      -migration
      -phototropism- growing towards the light
    • physiological- process inside an organism
      -kidney adaptations
      -toxin production
    • uses of phosphates: make RNA,DNA, ATP, ADP, membranes, phosphorylation
    • why clear zone around each paper disc
      antibiotics diffuse out of paper disc and inhibit growth and kill bacteria
    • aseptic technique
      • flame any instruments to kill microorganisms
      • disinfect work surfaces to kill microorganisms
      • lift lid of petri dish only slightly so unwanted microbes don't contaminate culture
      • use bunsen burners to create a convection current
      • wash hands to kill microbes
    • degenerate - several codons code for one amino acid
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