bio mod 6

HideShow resource information
View mindmap
  • mod 6
    • 1) cellular control
      • mutations w/ mitotic division= somatic= not p***ed to offspring (e.g. cancerous tumors)
      • mutations w/ meiosis & gamete formation= may be inherited by offspring
      • gene mutations affect protein production + formation
        • types= point (replace) + insertion/deletion (frameshiift)
      • mutations= 1. spontaneous during DNA replication before cell division           2. mutagenic chemicals e.g. tar in tobacco, ionising rad- U.V, Xrays, gamma rays
        • expanding triple nucleotide repeats= a repeating triplet code e.g. CAG , num of repeats increases at meiosis  + again from generation to generation
      • regulating gene expression
        • transcription factor (TF)= protein/ short non-coding RNA combines w/ specific site on DNA + inhibits or activates transcription of that gene
          • operon= group of genes that function as 1 transcription unit
        • PROKARYOTIC cells; enzymes for specific conditions synthesised @ varying rates
        • EUKARYOTE CELLS- hav same genome but diff cells used + function differently; cell differentiation. All cells exppress basic housekeeping genes but e.g. genes expressed in neurones diff to in kidneys
          • TF slide down DNA, seek + bind to specific promoter regions;aid / stop attachment of RNA Polym to DNA & activate or suppress transcription of gene
            • TF IMPORTANT= make sure diff genes in diff cell types expressed
            • SOME TF involved in regulating cell cycle; tumour suppressor genes+ proto-oncogenes help reg cell division; mutation can lead to uncontrolled cell division or cancer
              • human genome project' mutation to genes for TF also lead to diseases e.g. cancer, autoimmune d
          • Chromosome translocation= piece of chromosome breaks off + attaches to another chromosome,; causes genetic abnormalities bc genes become too separated from promoter regions; gene expression not properly regulated
        • lac operon; E Coli normally metabolise glucose (Resp subst) Glucose absent, lactose (disacharide) present, lactose induces production of enzymes
          • lactose permease= lactose to enter bact cell
            • lactose NOT the absense of glucose that induces enzymes
          • B-galactosidase = hydrolyses lactose to glucose + galactose
            • promoter region= where RNA polymerase binds
              • operator + promoter = control sites
          • lac operon= 6000 b.p.; lacZ & lacY r structural genes; z=Bgalactosidase, y=lactose permease
      • post transcriptional gene reg
        • some introns= protein, some = short non coding lengths of RNA for gene reg. A length of DNA, according to how its spliced, encode for >1 protein
        • All of DNA= transcribed, makes primary mRNA- edited & mRNA introns removed. Remaining exons joined. Endonuclease enzyme= editing + splicing
          • transcription part = downstream of promoter region. (upstream = enhancer region= initiates or enhances transcription)
        • intron= non-coding regions of DNA; not expressed // exons = coding/ expressed
      • genetic control of body plan development
        • APOPTOSIS= programmed cell death
          • apop= 1) enzyme breaks cell cytoskeleton 2) cytoplasm = dense,      3) plasma membrane has small protrusions= BLEBS. 4)chromatin condenses, nuclear envelope + DNA break into fragment 5) cell breaks into vesicles; ingested via phagocytic cells
          • control apop; cells which reg cell cycle release signalling molecules for apoptosis to respond to int + ext stimuli e.g. stress. Molecules = cytokines from immune system cells / hormones / growth factors / nitric oxide; NO induces apop by making inner mitochondrial membrane more permeable to H+ & lowers H+ gradient, proteins get released into cytoplasm which bind to apoptosis inhibitor proteins + allow apop to occur
          • apop= integral part of plant & animal tissue development; extensive proliferation of cell types prevented by pruning w/ apop, without needing to release hydrolytic enzymes that could damage surrounding tissue
            • apop removes harmful/ ineffective T- lymphocytes at immune system development
              • rate of cells dying should equal rate of cells produced by mitosis; not enough apop = tumours, too much= degeneration. Cell signalling helps balance
        • (HS) homeobox sequence= 180 bp (not introns) within genes involved in regulating patterns of anatomical development in animals, fungi + plants
          • homeotic genes control anatomical development aka morphogensis so all structures in correct location w/ body plan... these genes contain homeobox sequences
          • HS encode 60 aa called a homeodomain (HD) sequence; folds into particular shape to bind to DNA + regulate transcription of adjacent genes. called Transcription factors and act within cell nucleus; shape called H-T-H.
            • shape H-T-H bc 2- alpha heices w/ one Turn // part of homeodomain aa seq recognise TAAT seq of enhancer region of gene to be transcribed
        • COLINEARITY = phenomenon where sequential and temporal (in time) order of gene expression corresponds with seq and temp development of various body parts
        • HG regulated by gap genes + pair-rule genes which are regulated by maternal mRNA from egg cytoplasm
        • homeobox + Hox genes help reg cell cycle by ensuring each daughter cell has full genome and is clone of parent. During cell differentiation, some genes in specific cells switched off bc not needed so not expressed.   Normal body cells divide limited num of times before dying
    • 2) patterns of inheritance
      • genotype= genetic make up // phenotype= visible characteristcs
      • mutagens= PHYSICAL= Xray,gamma, U.V. CHEMICAL= mustard gas, NO, free radicals, colchicine BIOLOGICAL= viruses, transposons (jumping genes, remenants of viral nucleic acid thats incorporated into genome), food contaminants e.g. mycotozins from fungi
      • mutations during gamete formation= persistent (transmit thru many generations w/o change) or random (not directed by a need on the organism part they occur on)
      • chromosome mutation= 1)deletion (part of chromosome lost, contain genes + reg seq lost.
        • 2) inversion= section of chromosome broken & turn 180o; genes still there but may be too far frm reg region to propr express
          • 3)translocation= piece of chromosome breaks off + attached to another chromosome, may interfere with translocated chromosome
            • 4)duplication= piece of chromosome duplicated, overexpression=harmful bc too main proteins or gene reg nucleic acids csn disrupt metabolism
              • 5)non-disjunction= one pair of chromosomes/ chromatids fail to seperate so one gamete has extra.- resulting zygote has extra, e.g. down syndrome
              • aneuploidy= chromosome num not multiple of haploid (failed separation in meiosis), polyploidy= diploid gamete fused w/ haploid, make triploid
      • variation from sexual repro- leads to evolution; during meiosis; crossing over alleles in prophase 1, independent ***ortment of chromosomes metaphase/ anaphase 1. Indep *** chromatids metaphase/ anaphase 2, random fusion
      • env factors; phenotypic variation, not p***ed through genes, some env factors prevent expression of genes .e.g. chlorosis bc Mg not available
      • monogenic= determined by single gene
      • punnett square= represents all possible random fertilization events
      • etoilation= plants grow abnormally long + spindly bc not enough light
        • autosomes= fully ****logous; match length + same genes at same loci
      • codominance= both alleles in genotype of heterozygous contribute to phenotype// Both resposible for 2 distinct + detectable gene products
      • sex linkage= 22 pairs of chromosomes = autosomes
      • autosomal linkage= gene loci present on same autosome that're often inherited together; bc chromosome not the gene is linked and cannot undergo independent ***ortment so inherited together
        • autosomal linkage; dont undergo crossing over in prophase 1 in meiosis
      • epistasis= interaction of non-linked gene loci where 1 masks expression of the other
        • 1)genes work antagonistically; recessive epistasis (****z; presence off recessive allele at 1st locus = epistatic to 2nd locus) ratio= 9:3:4
          • 2)antagonistically= dominant epistasis; presence of dom allele suppresses expression of other allele even if its dominant. ratio= 12:3:1 and 13:1 (both suggest dom epistasis)
            • 3) complementary fashion= 9:3:4 (suggests recessive epistasis) + 9:7 (bothh suggest epistasis by complementary gene action)
              • expl as; genes working to code for 2 enzymes that work in succession, catalyzing sequential steps of a metabolic pathway
        • in epi; gene loci not linked so ***ort independently during gamete formation
          • epistasis reduces genetic variation
        • autosomally inherited linked with genes CROSSING OVER or NO CROSSING OVER; crossing of non-sister chromatids in meiosis// with crossing; recombinant gametes can form; not in 9:3:3:1 ratio. Further apart 2 gene loci on chromosome= greater chance of recombinant gametes forming
      • chi2= determines if significance between observed + expected results is significant or due to chance
        • chi can be used when; data in non-contin catagories, strong bio theory, large sample size, data r raw counts, no zero scores
      • dihybrid= involving 2 gene loci
      • dihybrid crosses; alleles of 2 genes inherited independently of each other so each gamete has 1 allele for each gene locus,& during fertilisation any 1 allele pair can combine with any other 1
        • dihybrid characteristics e.g. seed colour + wrinkled; when 2 independent events occur simultaneously; product of individual probabilities = combined prob of occurence
          • many gardeners seeds = F1 gens so plants will exhibit specific desired phenotypic traits but wont breed true so new seeds needed next year
      • multiple alleles= characteristics for which 3+ alleles in pop gene pool (but individuals can only poses 2 on each gene locus)
      • sex linked= gene present on 1 of sex chromosomes
        • males= functionally haploid for X-linked disease bc cant be hetero or ****
          • in eukaryotes, num of linkage groups same as num of autosome pairs e.g. humans=22 linkage grps
      • null hypothesis= "there is no statistically significant difference between the observed & expected data. Any difference is due to chance"
      • variation
        • continuous v= produces phenotypic v where quantitative traits vary by small amouts (polygenic)
          • many genes involved in characteristics; each contribute to phenotype; have additive effect; more gene loci involved, greater range of phenotype
            • environment has greater effect on polygenic than mono
        • discontinuous v usually determined y alleles of single gene locus; monogenic. diff gene loci have diff effects on same characteristic
        • genes at diff loci may interact to influence 1 gene loci; makes discontin, v as in epistasis
        • directional selection= type of natural selection where env change favours new phenotype so change in pop mean (used by plant breeders for desired traits)
        • founder effect= small sample of original pop establish in new area; gene pool not very diverse (special case ofgenetic drift)
        • genetic bottleneck= sharp red in size of pop due to env event e.g flood/habitat destruction; reduces genetic diversity, as pop expands less diverse then before (e.g. selectively bred species) Can cause increase in freq of harmful alleles;risk to resulting pop
          • in nature; directional + stabilising may alternate
          • genetic drift can arise after a genetic bottleneck or as result of founder effect
            • genetic drift= loss of alleles from pop so  as pop recovers and size increases, it has less genetic diversity than before
        • stabilising selection= natural selection leads to constancy within pop, intermed pheotypes favoured, extremes removed; reduces genetic variation
        • disruptive selection= favours extreme phenotypes
      • Hardy-Weinberg principle
        • principle ***umes; -pop large enough to make sample error neglible, random mating, no selection, no mutation, no migration, no genetic drift
          • p+q=1 (alleles) p2+q2+2pq=1 (whole organism)
        • population (pop)= members of species living in same place, same time, that can interbreed
      • isolating mechanisms
        • allopatric speciation; 2 diff species from 1, due to geographical isolation (also barrier to gene flow)
          • allo:mutations not shared+ diff selection pressures+ diff allele freq
            • allo- genetic changes result of mutation/ selection/ genetic drift
        • speciation= splitting of genetically similar pop into 2+ to undergo genetic differentiation & eventually reproductive isolation, leading to evolution of new species
        • sympatric speciation= forming 2+ species bc reproductive isolation while pops inhabit same geographical location
          • sym:biological + behavioural changes.// Due to; mutations (wakeup late) genetic changes (change in chromosome num)
            • change chromosome num; prevent gamete fusion, zygotes less viable, infertile hybrid offspring.// mutation= change in courtship behaviour, animal genitalia
        • sub-species= pops are different but can still interbreed
      • artificial selection
        • e.g. plants; increased yield, pest + disease resistance, withstand low temps, high salinity
          • grow plants in high saline; doesnt make them tolerable just see which plants have mutation to survive
        • selective breeding programme = 20 yrs; produce new breeds
        • artificial selection (AS)= selective breeding of organisms, humans choosing desired phenotypes individually, so selecting genotypes that contribute to gene pool of next gen
        • invitro fertilisation, embryo cloning + artificial insemination, embryo transplant used in selective breeding of livestock & use tissue culture to make many plants from parent plant
        • inbreeding depression= related individuals crosses, more chances of inheriting 2 copies of harmful recessive allele
    • heterozygous ratio= 9:3:3:1 (mendelian ratio)

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »