Date of Award

Spring 1994

Project Type

Dissertation

Program or Major

Zoology

Degree Name

Doctor of Philosophy

First Advisor

Thomas D Kocher

Abstract

The complete nucleotide sequence of the sea lamprey (Petromyzon marinus) mitochondrial genome has been determined using purified, intact mtDNA. The lamprey mitochondrial genome is 16,201 bp in length, and contains genes for 13 proteins, 2 rRNAs, 22 tRNAs and 2 major non-coding regions. The genome displays several minor rearrangements but is basically colinear with other vertebrate genomes.

The sequence suggests that the vertebrate mitochondrial genomic organization was established at an early stage of vertebrate evolution. Comparisons with teleost and mammalian mitochondrial control regions demonstrate that some conserved sequence blocks have arisen recently. The overall base composition of the genome is similar to those of other chordate mitochondrial genomes. However the base composition at the wobble positions of four-fold degenerate codon families is strongly biased toward thymine.

Using amino acid sequences of nine other vertebrate and sea urchin mitochondrial protein genes, the phylogeny and estimated rates of evolution among vertebrate lineages were obtained. The estimated rate of sequence divergence in the warm-blooded vertebrates is generally faster than in the cold-blooded vertebrates. However, this result may be attributed to the uncertainty of fossil records and rapid saturation for amino acid substitutions. Therefore, conclusions about relative rates of amino acid substitutions should wait for methods which account for the pattern of sequence saturation, as well as additional sequence data which may reveal the complete record of substitution in these genomes.

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