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organelles.md

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Organelles

up until now focused on nuclear genome

label mito and chloro

eukaryotes defined by presence of nucleus and organelles

Endosymbiosis

first eukaryotes likely formed as infoldings -> nucleus

aquisition of mito -> respiration in increasingly oxygenated environ. both originated as endosymbionts

alpha-protobacteria or cyano taken up by archaea

as oxygen increased in atmosphere -> aerobic respiration a plus

some lineages took up cyanobacteria -> photosynthesize

some euks (giardia & some amoeba) have subsequently lost mito

Endosymbiosis

multiple independent endosymbiotic events for autotrophs

secondary (and teritary) endosymbiosis of other eukaryotes

Crosses and inheritance chloro

heteroplasmy vs. homoplasmy

by random dreplication/division (fig. 19.4) var. branch -> green or white

var. branch flowers -> green/white/var. offspring

Inheritance in mammals

inheriteance of mito in mammals -- always maternal

so mitochondrial diseases (some deafness, muscle myopathy)

blindness pedigree: normal, incomplete penetrance how explain incomplete penetrance? (interaction, environment, heteroplasmy)

label

  • oocyte development-
  • mutant (blue mito)
  • unaffected
  • intermediate
  • affected offspring

Not always maternal

  • redwoods both male
  • some pine trees, cpDNA male, mtDNA female
  • mussels have double uniparental: F mito is maternal, M mito is paternal

Organellar - nuclear interaction

wild type plants produce two mito genes MG1 and MG2

multiple origins of novel ORF (what's an ORF?)

sterile pollen grains don't stain

sterility cosegregates w/ RFLP cutting extra ORF

possible use of CMS?

Mito genome

few kb-megabases in size

not all circular, some linear

less restictive wobble rules

Mito code differs for some codons in some species

thus fewer tRNAs, also some coded for in nuclear genome

label:

  • rRNA (red)
  • mRNA (blue)
  • tRNA (black lines)

heavy strand (inside); literally has higher mass b/c mroe G's and A's

  • in humans mostly protein coding and tRNA

light strand (outside)

3 promoters

  • HSP1, HSP2, LSP (promoters for heavy light strand)

trasncription happens from 3 promotoers

then cleaved to separate pieces

in many species, mito D loop used for DNA barcoding (explain)

  • D loop is 3-stranded displaced as part is replicated by stops

in plants mito genomes mutation rate is very low but rearrangements common

in animals fewer rearrangements

Chloro genome

few hundred kb ina size

fewer rearrangements than mito genome

ribulose-1,5-biphosphate caroxylase oxygenase (top left)

  • needed for photosynthesis, ~50% protein plants
  • most abundant protein on earth (good guess on protein question test)
  • made up of rbcL in chloroplast and rbcS subunit in nucleus

polycistronic transcription & translation

no deviation from code, no extra wobble rules, make own tRNAs

slow mutation rate ~1/3 of nuclear

Gene transfer

label:

  • mito
  • chloro
  • nucleus
  • proteins
    • blue host
    • red mito
    • green chloro
  • cyanobacterium
  • protein function:
    • in chloro
    • mito
    • other nonorganellar
  • dashed arrows: continued transfer