D3.7 Evidence for evol part III

jackie

Biochemical evidence provided by the universality of DNA and protein structures for the common

ancestry of living organisms. DNA structure is universal, i.e.,

the same in all organisms, composed of polymers of the same four nucleotides: adenine, guanine, cytosine, and thymine

Protein structure is universal, composed of polymers made of the same 20 amino acids

Genetic code is universal: The genetic code whereby DNA is transcribed into RNA and then translated into proteins is universal, so that all organisms use the same codons for determining amino acid sequence

Biochemical evidence provided by the universality of DNA and protein structures for the common ancestry of living organisms.

Summary: because all of the basic biochemistry of genetic information and protein synthesis is identical in all organisms, they likely inherited it from a common ancestry

How variations in specific molecules can indicate phylogeny.

Globins: hemoglobin and myoglobin • globin genes are present in all animals and some plants

• the greater the similarity in the globin genes of two species, the less time has passed during which mutations could accumulate, and thus, the degree of similarity can be used as a measure of how closely related the two species are

• the greater the similarity in a protein produced by two species, the more recently they shared a common ancestor

• the greater the difference in a protein produced by two species, the more distantly they shared a common ancestor

How variations in specific molecules can indicate phylogeny.

For example, the hemoglobin of gorillas only differs by one amino acid from human hemoglobin whereas elephant hemoglobin differs from human hemoglobin by 26 amino acids.

Therefore elephants separated as a species from a common ancestor with humans longer ago then did gorillas.

Information like this can help to group organisms in trees of descent and suggest how long ago they had a common gene pool

How biochemical variations can be used as an evolutionary clock Hemoglobin varies between vertebrates: Hemoglobin, a blood

protein found in all vertebrates, shows amino acid differences compared to humans in of a variety of vertebrates: • horse: 18 • mouse: 16 • reptile: 35 • frog: 62 • shark: 79

Calibrate variation to time: Hemoglobin amino acid differences correlate to geological time based on fossil record: • mammals: originated 70 million years ago • reptile: originated 270 million years ago • frog: originated 350 million years ago • shark: originated 450 million years ago

How biochemical variations can be used as an evolutionary clock Establish a variety of molecular

clocks: • Hemoglobin changes at a

regular rate over hundreds of millions of years, acting as a molecular clock.

• A variety of proteins have been studied, each producing its own molecular clock.

• Histones (organize DNA) hardly change at all.

• Cytochrome c (a mitochondrial protein) changes slowly.

• Hemoglobin (blood protein) changes moderately.

• Fibrinopeptides (clotting proteins) change rapidly