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DSST Anthropology as a Discipline

Reproduction to that of another is known as gene flow

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reproduction to that of another is known as gene flow . Also called gene migration, gene flow usually occurs in humans as a result of actual migration of populations (either forced or voluntary). Watson and Crick first described a successful model of DNA, popularly known as the Double Helix. DNA, which stands for Deoxyribonucleic Acid, is the genetic material which contains all of our hereditary information which is passed from parents to children. A chunk of DNA which contains the info for producing a specific protein is known as a gene. A collection of genes make up X-shaped structures called chromosomes. A mutation is an alteration in the genetic material of a cell that is transmitted to the cell's offspring. This may be spontaneous (the result of accidents in the replication of genetic material) or induced by external factors (e.g., radiation and certain chemicals can cause mutations in the DNA). The arrangement of nitrogenous bases determines the genetic code of an organism. The "letters" in the DNA Code are the nitrogenous bases. There are 4 different bases (A, C, T, and G), and combinations of these spell out the genetic code of an organism. Mutations occur when one base is substituted for another or when one or more bases are inserted or deleted from a gene . Mutations may occur naturally or due to the presence of mutagens (things which cause mutations)--like radioactivity. Genetic recombination refers to the exchange between two DNA molecules. It results in new combinations of genes on the chromosome. In crossing over, two chromosomes break at corresponding points, switch fragments and rejoin. The result is two recombinant chromosomes. In bacteria, crossing over involves a chromosome segment entering the cell and aligning with its homologous segment on the bacterial chromosome. The two break at corresponding point, switch fragments and rejoin . The phenotype is the observable characteristics of an organism, including physical appearance. The genotype for a person tells us what genes they have. The phenotype is the observable result of the genotype. For example, a person's genotype for hair color might be one gene for brown eyes from the mother, and one gene for blue eyes from the father. The person's phenotype would be brown eyes. Gregor Mendel showed (1) that heredity is transmitted through factors (now called genes) that do not blend but segregate, (2) that parents transmit only one-half of the genes they have to each child, and they transmit different sets of genes to different children, and (3) that, although brothers and sisters receive their heredities from the same parents, they do not receive the same heredities (an exception is identical twins). Mendel thus showed that, even if the eminence of some ancestor were entirely the reflection of his genes, it is quite likely that some of his descendants, especially the more remote ones, would not inherit these "good" genes at all. In sexually reproducing organisms, humans included, every individual has a unique hereditary endowment.
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