Bio FINAL review ch13-16, 19tttt

Bio FINAL review ch13-16, 19tttt - Bio FINAL review Chp...

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Bio FINAL review Chp 13-16, 19 CHAPTER 13: Mendel and the Gene: Patterns of Inheritance Mendel examined pea traits o Single gene, 2 alleles Monohybrid cross o Crossing of one trait Law of Segregation o 2 alleles separate during meiosis and end up in different gametes Law of Independent Assortment o Allele pairs separate independently from each other o The alleles or traits have nothing to do with each other o Ex: Height will not interfere with color genes Alleles o Variations of a single gene Homozygous o 2 identical alleles for a gene Heterozygous o 2 different alleles for a gene Genotype o Genetic description Phenotype o Physical description Dominant o Allele that determines organism’s physical appearance requiring at least one copy Recessive o Allele that has no noticeable effect on organism’s phenotype when paired with a dominant allele o Displays phenotype only when recessive homozygous Test cross o Determine unknown genotype by crossing with known homozygous recessive Codominance o Both traits are equally expressed on offspring o Don’t blend together o Ex: black + white = spots of black and white Incomplete Dominance o Heterozygous phenotype is distinct from either homozygous phenotype o Both traits are mixed/blended together o Intermediate phenotype o Ex: black + white = grey Other effects of genes
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o Lethal alleles Causes animals to die o Multiple alleles for one gene Ex: blood groups (slide 18) complicated o Pleiotrophy Single gene with many phenotypes Ex: sickle cells o Polygenic traits many genes with one phenotype ex: height, eye/hair/skin color o Epistasis Gene at one locus affects phenotypical expression of another gene at another locus (slide 21) Ex: yellow Labradors particular gene in yellow dogs that makes their coat yellow but still have black skin o Environmental effects on gene expression Internal/external environments influence phenotype Temp, chemicals, nutrition Pedigree o Following an expression through generations o Like a big family tree to map a certain gene and where it came from o Used to help isolate gene associated with disease o X-Linked = more men affected with disease Sex determination o Depends on species Mammals = F: XX and M: XY Some insects = F: XX and M: X Birds = F: ZW and M: ZZ Bees = females have twice the # of chromosomes as males X and Y chromosomes o Pair up during metaphase o X-linked: genes on X chromosome o Y-linked: genes on Y chromosome o SRY: sex determining region on Y; gene on Y chromosome Sex-linked disorders o Affect mainly males o Don’t have an extra X chromosome like females do to cancel out the disorder Independent assortment vs linked genes o I.A.: two or more genes are far apart and will have nothing to do with each other; follows mendel’s ratios o L.G.: two genes are close together on same chromosome will be inherited together; does not follow mendels ratios
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Recombinant gametes o
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