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Unformatted text preview: n = number of loci with two alleles that inﬂuence the
characteristic. Polygenic Traits • So, if there are 8 loci, 38 = 6561 different genotypes.
• Many different phenotypes with only slight differences.
• Add in the environment, and there’s even more variation
• We’ll return to quantitative traits later (assuming we have time) Chapter 6: Genetic Model Organisms • Genetic model organisms
– Why and how we use them
– Examples Genetic model organisms: why? • The vast majority of organisms
– Use the same genetic material (DNA or RNA)
– Use the same genetic code
– Use many of the same genes to accomplish the same tasks.
• Indicates that all life on earth evolved from the same primordial
ancestor (3.5-4 billion years ago)
• Thus, the study of other organisms can provide insight into
human biology, and ultimately the treatment of disease. Genetic model organisms
• Organisms with characteristics that are particularly useful for genetic
• short generation time
• large number of progeny
• adaptable to lab environment
• housed and propagated relatively inexpensively
• genomes sequenced (recently) Genetic model organisms
• 7 major genetic model organisms
– Escherichia coli - a bacterium in the human gut
– Saccharomyces cerevisiae - baker’s/brewer’s yeast
– Caenorhabditis elegans - a microscopic nematode (round worm)
– Drosophila melanogaster - fruit ﬂy
– Danio rerio - zebraﬁsh (newbie - sequencing ongoing)
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