Genesis: Heredity, our genes and evolution

Evolution Intro History of Evolution Voyage of the Beagle Darwin's Theory Heredity Natural Selection Evolutionary theory after Darwin The story of time (Primeval Soup) Conclusion of evolution.

The links in the body of this page are for our	Darwin’s Theory depends on traits and characteristics being passed along from parent to child, that is, between generations. Evolution couldn’t take place without this process, which is called heredity. Gregor Mendel (1822-1884) was an Austrian monk who discovered the basic rules of heredity by experimenting with pea plants. He studied characteristics such as the colour of the flowers, height variation and the texture of the seeds. From this he studied inheritance, the process of passing characteristics to the next generation of plant, and he came to several conclusions – The characteristics of an organism are passed along from parent to child by pieces of information called genes. Every gene represents a single bit of information containing one characteristic. Alleles are two or more genes that carry a piece of information about a single characteristic, for example: one of the allele pair may be for blue eyes and the other may be for brown. Alleles are usually found in pairs, one of which is dominant, or over powering, and one recessive which is masked by the dominant. In reproduction each gamete, or reproductive cell, (sperm or egg), has only one of the pair present. If a dominant and a recessive allele are both present, the individual will be affected by the dominant allele. Mendel’s observations were later shown to apply also to animals by the American scientist T H Morgan. This idea can be investigated by examining the human trait of being able to roll the tongue. If the correct heredity gene is found in a human, the muscle which enables the tongue to be rolled is produced. Before reproduction, sex cells are created through the process of meiosis. These cells will contain either of two genes for tongue rolling, one that produces the muscle or one that doesn’t. In reproduction, each parent will provide one of these genes to the child. In humans the “rolling gene” is dominant; therefore, if a “rolling gene” is present the child will have the ability to roll his or her tongue. There are three possible outcomes: two “rolling genes” are present and the offspring develops the muscle. Subsequently, all the offspring’s children will have the ability. one of each gene is present. Because the rolling gene is dominant, the muscle will develop. They will have 1/2 rolling and 1/2 non-rolling gametes. two non-rolling genes are present. The muscle therefore can not be developed. Only recessive genes will be passed to offspring. The tongue rolling gene is passed along generations; therefore, it is a hereditary trait. Although Darwin didn’t know of Mendel’s discoveries, Darwin applies some of these ideas by suggesting that inherited traits can give individuals a better chance of survival, which is shown in Natural Selection.
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