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34 Cards in this Set
- Front
- Back
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Genes
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Genes: units of instruction, located on chromosomes, that produce or influence a specific trait in the offspring
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Genetics
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The study of the mechanisms of heredity and biological variation |
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Inheritance
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The process by which different traits are inherited from parents to their offspring
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Heredity
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The passing of traits from parents to offspring
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Aristotle
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4th Century BC, believed inheritance factors were located in the blood (ex. bloodline)
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Numerous Greek Philosophers
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Believed that the issue of heredity was based upon the sex that dominated in the sexual act
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Linneaus
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18th Century, offered a two-layer theory: -the outer systems came from the father -the inner systems came from the mother |
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Preformation
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Aristotle-17th Century, it assumed that a human was no more than the unfolding of what was already present. (All present generations were encased in the bodies of their ancestors) Ovists- believed organisms are in the egg Spermists- organisms are in the sperm |
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Inheritable traits are:
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Found in very small chemical packages Difficult to measure and quantify Often affected by the environment Often very complex Takes a long time to unfold (humans) |
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Gregor Mendel (father of genetics) 1822-1884
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Czech born monk, monk for his study of the inheritance of traits in peas Realised the bests traits to study of heredity were obviously present or completely absent |
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Mendel's Principle of Inheritance
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Inherited traits are transmitted by genes which occur in alternate forms called alleles -Principle of Dominance -Lawof Segregation -Law of Independent Assortment |
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Principle of Dominance
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When 2 forms of the same gene are present the dominant allele is expressed
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Law of Segregation
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In meiosis two alleles will separate so that each gamete receives only one form of the gene (Anaphase 1)
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Law of Independent Assortment
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Each trait is inherited independent of other traits (chance)
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Characteristic
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A distinguishing feature or attribute ex. height, color |
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Phenotype
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Observable and inheritable traits ex. short, color |
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Genotype
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Specific arrangement of alleles for a trait, leads to a phenotype ex. tt for short |
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Allele
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Two or more alternate forms of a gene ex. T for tall, t for short |
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Dominant
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Producing the same phenotypic effect whether paired with an identical or dissimilar allele ex. T is expressed if Tt or TT |
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Recessive
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An allele that does not produce a phenotypic effect when heterozygous with a dominant allele ex. t will only be expressed if tt |
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Homozygous
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A genotype that contains the same allele for a trait ex. TT, tt |
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Heterozygous
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A genotype that contains two different alleles for a trait ex. Tt |
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Monohybrid Cross
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A cross between 2 individuals that differ in one trait
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Dihybrid Cross
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A cross between 2 individuals that differ in 2 traits
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Test Cross
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A cross between an unknown individual and a homozygous recessive individual to determine the unknown genotype
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True Breeding
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Organisms that are homozygous for traits and produce offspring that exhibit the same characteristics generation after generation
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Paternal Generation (P)
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The 2 individuals crossed in a breeding
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Filial Generation
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Offspring from a cross (F1) offspring of a paternal cross (F2) offspring of a cross of the F1 generation |
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How to write it
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Dominant alleles are uppercase letters, recessive alleles are lowercase letters When writing the genotype the dominant allele always comes first ex. Aa (monohybrid), AaBb (dihybrid) |
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Monohybrid Crosses
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Look at a single traits that result from two alleles combining
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Mendel's First Experiment
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Monohybrid cross Purebred tall and short plants P: TT x tt F1: Tt (100% tall) F2: TT, Tt, tt (75% tall, 25% short) |
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Simple Dominance
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Two possible phenotypes ex. yellow or green Three possible genotypes ex. GG, Gg, gg When two purebred phenotypes are crossed only one will show in the offspring (F1) -phenotype expressed is dominant -phenotype hidden is recessive If offspring F1 are crossed F2 will show 3:1 ratio of dominance to recessive phenotype |
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Gametes
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Gametes are formed through meiosis -each gamete must have one allele from each gene (or letter pair) ex. Gg -> g, G |
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Test Cross
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Purpose: to determine the genotype of an individual with a dominant phenotypeDone by: crossing unknown dominant phenotype with a recessive phenotype-if all offspring are dominant phenotype then the unknown is homozygous-if any offspring are recessive phenotype then the unknown is heterozygous
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