Alternative
Vertebrate Genomes: nuclear & mitochondrial
DNA
The nucDNA genome in typical vertebrates
consists of several billion base pairs of DNA, arranged on paired chromosomes,
one inherited from each parent. The human genome shown here comprises 3
billion bp in 22 pairs of autosomal chromosomes and one pair of sex
chromosomes, XY in this
(male) individual.
The mtDNA
genome is a much smaller, circular
molecule about 16 ~ 18,000 bp in circumferance in most vertebrate
species.
The genome comprises 13 protein-coding regions,
two
rRNA genes, a replication control
region,
and 22 tRNA genes. The order of
these
is broadly conserved across vertebrates. There are no introns: splicing
out of tRNAs produces mRNA templates. The mtDNA
genome
is self-replicating with the aid of nucDNA-encoded
polymerases. The genome is locted is the extranuclear mitochondria, the "powerhouses of the cell," where it
contributes
to cell respiratory systems in the Cytochrome Oxidase, ATP
synthase,
and NADH systems. The vertebrate mtDNA
genetic code differs from the "Universal" code is several respects.
Unlike the nucDNA
genome, the mtDNA genome
is inherited solely through the cytoplasm of the maternal egg, and does
not undergo genetic recombination. It has therefore been widely used in
evolutionary and population biology to trace maternal lineages within
and between species.
