16-review - Genetics The study of variance and inheritance...

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Genetics The study of variance and inheritance in organisms. History of Genetics Early geneticists thought organisms changed in huge leaps (they were called mutationists ), while evolutionary biologists, who believed in a slower process, were called naturalists and were originally in opposition to the geneticsts. One of the most important events of the 20th century was the coming together of these once-opposing sciences into the modern synthesis of biology. Hippocrates thought that "seeds" were generated from all parts of the body and combined into pangenesis . Joseph Kolreuter did work with plants and found that the blending inheritance . Such dated ideas as the thought that blood had a role in reproduction gave rise to terms such as "blood brothers" or "royal blood". At one time, homunculi ("little men") were believed to be carried in sperm in a theory known as preformationism . Gregor Mendel is probably the most famous individual in the history of genetics. His work was largely ignored until it was discovered by three different men working independently in 1900. We think it was ignored for so long because the world was preoccupied with Darwin’s (still relatively new) ideas. Modern Genetics Our current theory is the particulate theory of inheritance . Our germ tissue contributes to reproduction, while our somatic cells ( soma means body) don’t. Genes are located in chromosomes, meaning "colored bodies" after the fact that they readily absorb certain dyes and were first seen by this method. Most people have 23 pairs of chromosomes, 22 autosomes and one sex chromosome from each parent. Ordinary cells divide to produce diploid cells in mitosis, while germ cells divide using meiosis to form haploid cells. Mendel’s Laws 1: the principle of segregation stated that traits are passed on by discrete factors, one from each parent. 2: the principle of independent assortment stated that all alleles assort independently during gamete formation (this is not always true). The Chromosome Theory of Inheritance
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This note was uploaded on 04/14/2008 for the course BIOL 115 taught by Professor Diggs during the Fall '07 term at Austin College.

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16-review - Genetics The study of variance and inheritance...

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