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Chloroplast DNA (cp DNA)

Plastid Genome
  • Exist in multiple copies
  • Each chloroplast has several nucleoid regions containing 8-10 DNA molecules
  • ds circular DNA
  • Genome size 120-150 kb of DNA
  • 46-90 protein coding genes, 2 rRNA  and over 30 tRNA genes.
  • Generally lack introns

  • Highly conserved throughout plant species
Chloroplast- Function
  • Grana: Light reaction or synthesis of ATP and NADPH (code LG: light reaction at grana)
  • Stroma: Dark reaction or CO2 fixation using energy  (ATP and NADPH) synthesised during light reaction
  • Thylakoid lumen: H2O splitting complex. 
Similarity between chloroplast and prokaryotes 

(That supports Endosymbiont theory)
  • Circular ds DNA.
  • Not covered by a membrane (nucleoid region).
  • Not associated with histone proteins.
  • Generally introns are absent.
  •  Small 70 S ribosomes.
  • Protein synthesis initiated by formyl methionyl tRNA (f-met tRNA).
  • Replication, transcription and translation similar to bacteria.
  • Transcription and translation are similar in chloroplasts and eubacteria: most chloroplast genes are transcribed as polycistronic units, their mRNAs are not capped, no poly(A) tails are added, and they possess a Shine Dalgarno ribosome binding sequence. 
  • The RNA polymerase of liverworts contains α and β subunits and the amino acid sequence has great similarity to those of E.coli.
  • DNA sequences in cyanobacteria which supports the endosymbiotic theory. Most cpDNA evolves slowly in sequence and structure

Endosymbiont theory

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