Chloroplast DNA (cpDNA) is circular, double-stranded DNA found in chloroplasts. cpDNA ranges in size from 120-2000kb depending on the species. It contains genes that encode components of the chloroplast protein synthesis machinery like rRNA, tRNA, and ribosomal proteins. It also contains genes for photosynthesis proteins. While cpDNA was originally derived from cyanobacteria, chloroplasts have become dependent on the plant cell nucleus for many genes as cpDNA has lost much of its original genetic information over evolutionary time. Comparisons of cpDNA sequences between species has provided insights into chloroplast and plant evolutionary relationships.

1. CHLOROPLAST- DNA
(cpDNA)
PRESENTED BY:
Noopur Joshi
(M.Sc. I Semester)
DEPARTMENT:
Biotechnology

2. INTRODUCTION TO CHLOROPLAST
• Chloroplasts are the most widely distributed plastids
and one of the most important of all.
• Their shapes vary from filamentous, saucer shape to
discoid or club shaped.
• Generally, they measure 2-3µm in thickness & 5-
10µm in diameter, however this measure changes
with the specie.
• Their no. in a cell remains constant for a specie but
may also vary with the specie and within the specie.

4. CHLOROPLAST AS A
SEMI-AUTONOMOUS ORGANELLE

5. RIBOSOMES OF CHLOROPLAST:
Are smaller than the cytoplasmic ribosomes.
Are of 70S type and resemble to those of bacterial
ribosomes.
They consist of two ribosomal RNAs; 23S rRNA and
16S rRNA.
Polysomes have also been reported to be found in
the chloroplast.
Aminoacyl-tRNAs, aminoacyl-tRNA synthetases and
methionyl-tRNA are also found in chloroplast.

6. cpDNA:
Salient Features

7. • Ris and Plant(1962),first reported DNA molecules in
the chloroplast of Chlamydomonas.
• The DNA molecule here is genreally double helical,
• Average length: 45µm i.e. about 135,000 bp
• Replication of chloroplast DNA has been followed
with ³H-thymidine.
• Genetic maps of chloroplast DNA have been
successfully made by the use of restriction enzymes.

8. The chloroplast DNA (cpDNA) codes for following:
• Choloroplast mRNA
• Chloroplast rRNA
• Chloroplast tRNA
• Chloroplast ribosomal protiens
• Certain structural proteins of thyllakoid membranes.
• The larger subunits of C Dase enzyme which weighs
about 55,000D

9. • In higher plants, cpDNAs range in size from 120-
160kb .
• In algae: 85-292kb choloroplast genomes are found
where the cpDNa is circular.
• In 2 species of green algae of genus Acetabularia,
the cpDNAs appear to be huge; about 2000kb.
• The large single chloroplast of Chlamydomonas
reinhardtii contains about 200 copies of the cpDNA.

10. • All the chloroplast genomes analyzed till now
contain the same set of genes, but with these
arranged very differently on the cpDNAs
• Genes present on cpDNAs can be grouped into 2:
1) Those that encode for the components of
chloroplast protein biosynthetic apparatus:
RNA pol subunits,
 structural components of chloroplast ribosome
subunits
Set of tRNAs

11. 2) Those specifying the components of the
photosynthetic machinery:-
 PS I
 PS II
 ETC
• The chloroplast genomes of higher plants are
about one-20th to one-30th the size of the genomes
of the prokaryotic genomes, from whcich they are
believed to have evolved( cyanobacteria).
• THUS, chloroplasts have lost much of the genetic
information of their ancestors, and have become
dependent much on nuclear genes of the host cell
for many essential components.

12. • Comparative studies of chloroplast genomes have
provided information about the evolutionary
relationship of plant and algal species.
• J.D.Palmer has distinguished 6 major lines of
chloroplast evolution.
• The chloroplast genomes present in different
evolutionary lines contain nearly the same genes
but in different arrangementson the cpDNA
molecules.

13. END