Theoretically, if a particular sequence of mtDNA could have mutated to yield the mtDNA sequences in modern humans, then that ancestral sequence may represent a very early human or humanlike female—a mitochondrial "Eve," or metaphorical first woman. one maternal line may have persisted.
Researchers in the mid 1980s compared mtDNA sequences for protein-encoding as well as noncoding DNA regions in a variety of people, including Africans, African Americans, Europeans, New Guineans,and Australians.
They deduced that the hypothesized ancestral woman lived about 200,000 years ago, in Africa
Many different types of organisms use the same proteins, with only slight variations in amino acid sequence. The similarity of protein sequences is compelling evidence for descent from shared ancestors—that is, evolution. Many proteins in humans and chimps are alike in 99 percent of their amino acids, and several are identical. When analyzing a gene's function, researchers routinely consult databases of known genes in many other organisms.
Cytochrome c is one of the most ancient and well-studied proteins. It helps to extract energy from nutrients in the mitochondria. The more closely related two species are, the more alike their cytochrome c amino acid sequence is ( table 16.3 ). Human cytochrome c, for example, differs from the horse version by 12 amino acids, and from kangaroo cytochrome c by 8 amino acids
The human protein is identical to chimpanzee cytochrome c. The homeotic genes, discussed in Clinical Connection 3.1, are another class of genes that has changed little across evolutionary time.
Companies have marketed DTC DNA-based tests for traits, susceptibilities, and genetic diseases. The tests range from the obvious (eye color) to the dubious (athletic ability) to the serious (cancers).
-Since then, the genetics community has repeatedly asked that genetic tests be included as a specialty area, to no avail. State regulations can override CLIA, but only if they are equally or more stringent. Therefore, the regulation
of genetic tests remains somewhat unclear.
- Even DTC tests for very well-studied mutations can lead to complications and confusion.
- A customer might not know that inheriting the genotype for HH is not the same as having the disease.
- An advantage of DTC genetic testing companies is that they are amassing tremendous data stores, which can be mined to make discoveries much faster than is possible with traditional research methods. Most company websites also provide information about genetics. However, some companies prey on consumer unfamiliarity with genetics.
- - "Although these recommendations may be beneficial to consumers in that they constitute common sense health and dietary guidance, DNA analysis is not needed to generate this advice." Some of the suggestions could even be dangerous, such as vitamin excesses in people with certain medical conditions