Mitochondiral DNA is -

Ans. is 'a' i.e.. Closed circular o This question is a direct repeat from AI-2006.o Human mitochondria contain two to ten copies of a small circular double-stranded DNA molecule that makes up approximately I % 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 plav key roles in the respiratorv chain.Some Major Features of the Structure and Function of Human Mitoctionriai DNAo Is circular, double-stranded, and composed of heavy (H) and light (L ) chains or strands,o Contains 16,569 bp.o Encodes 13 protein subunits of the respiratory chain (of a total of about 67) -Seven subunits of NADH dehydrogenase (complex I)Cytochrome b of complex IIIThree subunits of cytochrome oxidase (complex IV)Two subunits of ATP synthaseo Encodes large (16S) and small (12S) mt ribosomal RNAso Encodes 22 mt tRNA moleculeso Genetic code differs slightly from the standard code -VGA (standard stop codon) is read as Trp.AGP and AGG (standard codons for Arg) are read as stop codons.o Contains very few untranslated sequences,o High mutation rate (5 to 10 times that of nuclear DNA).o Comparisons of mtDNA sequences provide evidence about evolutionary origins of primates and other species.