2. Introduction
Mitochondria (singular: Mitochondrion) are membrane
bound organelles found in the cytoplasm of almost all
eukaryotic cells .
It’s primary function is to generate large quantities of
energy in the form of adenosine triphosphate (ATP).
Mitochondria are typically round to oval in shape and
range in size from 0.5 to 10 μm.
In addition to producing energy, mitochondria store
calcium for cell signaling activities, generate heat and
mediates cell growth and death.
Mitochondria are unlike other cellular organelles in that
3. Discovery
• Mitochondrial DNA was discovered in the 1960s by Margit
M. K. Nass and Sylvan Nass by electron microscopy and
by Ellen Haslbrunner, Hans Tuppy and Gottfried
Schatz by biochemical assays on highly purified
mitochondrial fractions.
4.
5. MITOCHONDRIAL GENOME
• Mt genome consists of a
circular chromosome 16.5kb in
size that is located in the
mitochondrial matrix .
• Most cells contain at least
1000 mtDNA molecules
distributed among hundreds of
individual mitochondria.
• It contains 37 genes, and
encodes 2 types of rRNA, 22
types of tRNAs and 13 proteins
subunits.
6. Genes encode 13 proteins that
are subunits of enzymes of
oxidative phosphorylation.
The remaining polypeptides of
the oxidative phosphorylation
complex are encoded by the
nuclear genome.
In most multicellular organisms,
the mtDNA - or mitogenome - is
organized as a circular, covalently
closed, double stranded DNA.
For human mitochondrial DNA
100-10,000 separate copies of
mtDNA are usually present per
cell (egg and sperm cells are
exceptions).
7. The two strands of mtDNA are differentiated by their
nucleotide content, with a guanine rich strand referred to
as the heavy strand (or H-strand) and a cytosine-rich
strand referred to as the light strand (or L-strand).
The heavy strand encodes 28 genes, and the light strand
encodes 9 genes for a total of 37 genes.
Of the 37 genes, 13 are for proteins (polypeptides), 22
are for transfer RNA (tRNA) and two are for the small
and large subunits of ribosomal RNA (rRNA).
10. Control Region
• The control region contains
the signals to control RNA
and DNA synthesis in the
mitochondria.
• It is also our fastest evolving
DNA sequence.
• This region of noncoding
DNA, also known as the
hypervariable region,
accumulates mutations at
approximately 10 times the
rate of nuclear dna,
• This region also called as D-
loop, relating to a structure
formed when the mtDNA
replicates.
11. Complex I Genes
• These seven genes (ND-1, ND-
2, ND-3, ND-4, ND-4L, ND-5,
ND-6)encode subunits of a
protein complex in the
mitochondrial membrane.
• The complex, NADH
dehydrogenase, is an electron
transporter that is involved in the
production and storage of
energy. Although the genes to
make the complex lie within the
mtDNA, the process of producing
energy requires molecules that
are produced outside the
mitochondria.
12. Complex III Genes
• This complex is part of the
electron transport chain of
mitochondria, involved in
generation and storage of
energy. This mitochondrial
gene encodes the
cytochrome b protein, which
is part of a complex in the
inner membrane of a
mitochondrion, known as
ubiquinol, or cytochrome c
oxidoreductase.
13. Complex IV Genes
• These three genes (MT-
CO 1, MT-CO 2, MT-CO
3) encode protein subunits
that are part of a complex
known as cytochrome c
oxidase.
• This complex acts as an
electron transporter during
the process of producing
and storing energy in the
mitochondria.
14. Complex V Genes
• These two genes (MT-ATP 6
and MT-ATP-8) encode
proteins contained within a
complex known as ATP
synthase.
• This protein complex,
located in the inner
membrane of the
mitochondrion, acts an
electron transporter in the
pathway that produces and
stores energy.
15. Ribosomal RNA Genes
• These genes, known as
16s and 12s rRNA,
encode ribosomal RNAs
(rRNA) used to build
ribosomes.
• During protein synthesis,
ribosomes assemble to
translate the messenger
RNA sequence into an
assembled protein. The
RNA produced by these
genes build the “molecular
machinery” to synthesize
16. Transfer RNA Genes
• These 22 genes encode transfer
RNA molecules. Each transfer
RNA is associated with a
specific amino acid ( protein
building block). Transfer RNAs
play a vital role in protein
synthesis, delivering their
associated amino acids to the
ribosome for incorporation into
new protein.
