Mitochondrial DNA (mtDNA) is a double-stranded circular DNA located in the mitochondria, consisting of 16,600 base pairs that code for 37 genes, including those for enzymes involved in oxidative phosphorylation. It exhibits maternal inheritance, meaning it is transmitted only from mother to offspring, and has a high mutation rate due to a lack of DNA repair systems. Diseases associated with mtDNA include cyclic vomiting syndrome and Leigh syndrome.

1. MITOCHONDRIAL
DNA
Sijo.A
B.sc.Botany & Biotechnology
Mar ivanios College

2. Mitochondrial DNA
 Mitochondrial DNA (mtDNA or mDNA) is the
DNA located in the mitochondria.
 They are double stranded circular DNA
molecule.
 It is only 16 kb in length – contains 16,600 bp.
 It is haploid in nature.
 It codes for 37 genes.
 13 genes provide instructions for making
enzymes involved in oxidative
phosphorylation.
 It is a process that uses oxygen and simple

3. Mitochondrial DNA
 Contains 22 tRNA and
2 rRNA coding genes.
 Contains only exons,
no introns.
 D
loop(D=Displacement)
is a DNA triple helix
where most of
replication and
transcription is
controlled.

6. HOMOPLASMY AND
HETEROPLASMY
 Homoplasmy:
 Homoplasmy is a term used in
genetics to describe a eukaryotic cell whose
copies of mtDNA are identical.
 Heteroplasmy
 Heteroplasmy is the presence of more than
one type of mtDNA which has a mixture of
both wild type and mutant DNA in a single cell.
 It is a rare condition and is often associated
with mitochondrial DNA diiseases.

7.  Maternal inheritance refers to the
transmission of genes only through the female.
 In higher animals, mitochondrial DNA
(mtDNA) shows maternal inheritance.
 During fertilisation, the sperm only contributes
its nucleus(23 chromosomes)
 Mitochondria of the sperm cell are located at
the mitochondrial sheath which is destroyed
upon fertilization.
 Only available mtDNA is that of the mother’s;
this is why mtDNA is of maternal origin.
Maternal Inheritance of
mtDNA

9.  The mitochondrial genome has a very high
mutation rate, 10 to 17 fold higher than that
observed in nuclear DNA. It is due to
(i) insufficient DNA repair system.
(ii) Lack of DNA proteins such as histones.
(iii) Spontaneous error arising during DNA.

10.  The diseases associated with mtDNA are:
1) Cyclic vomiting syndrome
2) Kearnes sayre syndrome
3) Cytochrome c oxidase deficiency
4) Leigh syndrome
5) Mitochondrial complexIII deficiency

11. THANK YOU…..