The forces of evolution through natural selection, gene flow, genetic mutation, genetic flow and genetic drift continue to act on human populations and have demonstrably altered allele frequencies since the origin of agriculture. These have brought interest to anthropologists, geneticists, doctors and many other people that several studies has been made which aim for the improvement of adaptation and cure of genetic diseases.
On June 24, 2004, msnbc reported about a German boy not yet turned 5, who possesses muscles that is double the size of other kids same with his age and half of their body fat. DNA testing showed that the boy has a genetic mutation that boosts muscle growth wherein the boy’s mutant DNA segment seemed to prevent the production of a certain protein called myostatin whose function is to limit the muscle growth.
Seven years prior to this news, researchers at Johns Hopkins University in Baltimore had led to the creation of a “mighty mice” by deactivating the gene that stimulates cells responsible for the production of myostatin. Researchers would not reveal the German boy’s identity but said he was born to a 24-year-old former professional sprinter that is rather muscular and the mother’s brother and three other close male relatives all were extraordinarily strong and one of them is a construction worker that can care and unload heavy curbstones using one hand.
One copy of the child’s gene that came from the mother is mutated while the other is normal and the boy has two mutated copies. One almost definitely came from his father, but no information has been revealed about the father. This kind of mutation is very rare in people (msnbc). Another example of genetic mutation in humans is the red hair color of some people like Peter Beattie, Nicole Kidman, Prince Harry and Michael Voss. According to genetic scientists red heads are becoming rarer and could be extinct in 100 years.
The current National Geographic magazine reports that less than 2% of the world’s population has natural red hair, produced by a genetic mutation in northern Europe thousands of years ago. Because redheads are only a small percentage present in the population and people are now intermingling across the globe which widens the availability of possible partners, the chance of red hair to red hair intercourse and producing red hair offspring are getting smaller, to the extent of being extinct.
The chances of having redhead becomes high if both parents are redhead. But offspring may or may not be redhead if only one of the parents is redhead. Therefore, if redheads are to be preserved, it is suggestive that people with red hair should marry Scots because an estimate of 40% of Scots carries the red gene and 13% actually have red hairs. Some experts say that people with red hairs could be extinct for as early as 2060, while others say the gene can be dormant for generations before recurring.
National Geographic says the gene at first had the positive effect of increasing the body’s ability for vitamin D production from the sunlight. However, because of worldwide interactions, today’s carriers are more susceptible to skin cancer and have increased sensitivity to heat and cold-related pain (“National Geographic Says Redheads Set for Extinction”). An example of genetic drift is the French Canadians in Quebec, who currently number close to 6 million, are all descended from about 8,500 founders who left France during the sixteenth and seventeenth centuries.
Because the genes carried by the initial founders represented only a sample of the gene pool from which they were derived, just by chance a number of alleles now occur in different frequencies from those of the current population of France. These differences include and increased presence of several harmful alleles, including those that cause some of the diseases such as cystic fibrosis, a variety of Tay-Sachs and thalassemia (Jurmain, Trevathan and Kilgore).
The high rate of Tay-Sachs disease among Eastern European Jews is attributed to a population bottleneck experienced by Jews in the Middle Ages. During that period, many Jews were persecuted and killed, and the population was reduced to a small fraction of its original size. Of the individuals who remained alive, there have been a disproportionate percentage of people who carried the Tay-Sachs gene. Since Jews in Europe remain isolated and did not intermarry with other Europeans to any great extent, the incidence of the trait remained unusually high in that population (Goldberg).
The distribution of several malaria-protective genes in the peninsula provides a clear example of a gene flow is the interaction of local differentiation and adaptation along with long distance gene pool linking the local with the wider regional gene pool. Many populations in the Malayan Peninsula were exposed to holoendemic malaria; some groups, including particularly some Orang Asli, continue to suffer from high rate of malaria. Several genetic traits that resist malaria have attained high frequency among the indigenous people of the peninsula.
The so called Duffy antigen provides the resistance to the disease (Morrison and Junker). The best documented example of natural selection in humans involves hemoglobin S an abnormal form of hemoglobin that results from a point mutation in the gene that produces part of the hemoglobin molecule. The allele for hemoglobin S, HbS is recessive to the allele for normal hemoglobin, HbA. People who are homozygous for the HbA allele produce normal hemoglobin. Heterozygotes (whose genotype is HbA / HbS) have a condition called sickle-cell trait.
Although some of their hemoglobin is abnormal, enough of it is normal to enable them to function normally under most circumstances. But people who enhirit the recessive allele from both parents i. e. , they are homozygous (HbS /HbS), have sickle cell anemia (Jurmain, Kilgore and Trevathan).
Works Cited
Goldberg, Deborah T. How to Prepare for the Ap Biology. How to Prepare for the AP Biology, 2004. Jurmain, Robert, Lynn Kilgore, and Wenda Trevathan. Introduction to Physical Anthropology. Thomson Wadsworth, 2005. Jurmain, Robert, Wenda Trevathan, and Lynn Kilgore.Essentials of Physical Anthropology. Thomson Wadsworth, 2006. Morrison, Kathleen D. , and Laura Lee Junker. Forager-Traders in South and Southeast Asia: Long-Term Histories. Cambridge University Press, 2002. msnbc. “Genetic Mutation Turns Tot into Superboy: 4-Year-Old Is First Documented Human Case, Scientists Say. ” msnbc (2004). March 3, 2008 <http://www. msnbc. msn. com/id/5278028/>. “National Geographic Says Redheads Set for Extinction. ” digitaljournal (2007). March 4, 2008 <http://www. digitaljournal. com/article/220229/National_Geographic_says_Redheads_set_for_extinction>.