Week 10 Notes
Week 10 Notes BSC 114
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This 2 page Class Notes was uploaded by Rebecca Sharp on Saturday April 16, 2016. The Class Notes belongs to BSC 114 at University of Alabama - Tuscaloosa taught by Stevan Marcus in Winter 2016. Since its upload, it has received 25 views. For similar materials see Principles Of Biology I in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 04/16/16
For Review Purposes Eukaryotic chromosomes are composed of DNA and protein Genes are composed of nucleotide sequences Mendel and Genes Mendel is the father of genetics. He followed thousands of pea plants and studied them, specifically their heritable factors, which we now call genes. o Alleles are specific genes, think of it like you have a gene for hair color and blonde is your allele. Alleles are the variations of their genes. Each gene hangs out in a super specific location within the chromosome called the gene’s ‘locus’, or in the plural, ‘loci’. When an organism has two identical alleles, it’s considered homozygous. When the alleles are different, it’s considered heterozygous. The P generation (or parent generation) is true breeding, which means that they’re homozygous. F1 is the name for the first generation of offspring, which are all heterozygous. F2, the second generation of offspring, is the interesting generation in which there’s real variation. o F2 is the generation where you really don’t know the genotype of the organism, so you can do a test cross. This where Punnet Squares come in to play. To do a test cross, you set up a punnet square with a recessive true breeding plant and the organism in question and the percentage of offspring displaying the recessive trait will let you know the genotype of the plant. If there are no offspring showing the recessive trait, you know the organism was homozygous for the dominant trait. If half the offspring show the recessive trait, then you know the test plant was heterozygous. The Concepts and Laws of Mendel Law of Independent Assortment; Each chromosome pair splits into paternal and maternal DNA independently from every other pair of chromosomes in the cell. o This only applies if the genes are far apart on the same chromosome, or if the genes are on different nonhomologous chromosomes. Genes that are located near each other on the same chromosome tend to be inherited together. Law of Segregation; Each of the alleles separate during gamete formation and thus end up in different gametes. Mendel’s First Concept; alleles account for variation in the F generations Mendel’s Second Concept; each organism gets an allele form mom and an allele from dad for each trait. Mendel’s Third Concept; if two alleles at a location differ, the dominant one will determine the appearance of the organism and the recessive one will be silent. Mendel’s Fourth Concept; both alleles separate during gamete formation and end up in different gametes. Mendelian Genetics don’t work if the traits are incompletely dominant, if the traits have more than two alleles, or when one gene is in charge of multiple phenotypes (called pleiotropy) o This happens in codominant traits, like the Speckled Havor Blossom. When a striped plant and a spotted plant are crossed, the offspring are both striped and spotted. o It’s called epistasis when a gene in one place effects a gene in another place. Like albinism. One gene codes for Will There Be Color, and another gene codes for Which Color to Be. o Quantitative Characteristics vary in a population along a gradient, like skin color in humans. o Polygenic Inheritance is the name for the additive effect of 2 or more genes on a single phenotype Some Info about Mendel’s Studies He bred garden peas in planned breeding experiments (all that means is that the parents are bred in a controlled setting and their offspring are analyzed) o In the pea plants mating was controlled by manually preforming cross pollination, which was done by rubbing pollen from one plant on the receptor of the other plant.) o Pedigree Analysis is what you do when you can’t do planned breeding experiments but still wat to study a subject. This is what we do for humans, because planned breeding experiments have been deemed immoral by the scientific community. Hybridization is the mating of two different true breeding plants o True Breeding means that were the plants allowed to self-pollinate, the offspring would be identical to the parent generation in all ways. Mendel studied 7 characteristics for pea plants; flower color, flower location, stem length, seed shape, seed color, pod shape, and pod color. Monohybrids; a cross between individuals that are heterozygous for one trait Dihybrids; a cross between individuals that are heterozygous for two traits
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