Mitochondrial DNA

Mitochondrial DNA is a closed circular double helix molecule which is transmitted maternally and is found within cells in multiple copies.
It contains 37 genes. All of these genes are essential.

All human cells contain two genomes: one in the nucleus and one in the mitochondria. 

• The mitochondrial genome contains only 37 genes
• Genome is maternally transmitted. 

A, B,C i.e. UGA codes for tryptophan, Codes for 13 protein, Circular double stranded DNA, Mitrochondrial disease occur due to Point Mutations and Large-Scale Rearrangements

B i.e. Maternally inherited

Ans. is ‘d’ i.e., Nemaline myopathy results due to mutations in mt- DNA

o Nemaline myopathy is not a mitochondria] disorder.

o Mitochondrial DNA is always maternally inherited.

o Heteroplasmy is the presence of mixture of more than one type of an organelle genome (mt- DNA) within a cell or individual. It is a factor for the severity of mitochondrial disease, since every eukaryotic cell contains many hundreds of copies of mt- DNA; it is possible and indeed very frequent for mutations to affect only some of the copies, while the remaining ones are unaffected.

 
Human mitochondria contain two to ten copies of a small circular double-stranded DNA molecule that makes up approximately 1% of total cellular DNA.
The majority of the peptides in mitochondria (about 54 out of 67) are coded by nuclear genes.
The rest are coded by genes found in mitochondrial (mt) DNA
This mtDNA codes for mt ribosomal and transfer RNAs and for 13 proteins that play key roles in the respiratory chain.