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27 Cards in this Set
- Front
- Back
Gene
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Genetic factor that helps determine a trait; often defined at the molecular level as a DNA sequence that is transcribed into an RNA molecule.
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Allele
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One of two or more alternate forms of a gene.
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Locus
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Position on a chromosome where a specific gene is located.
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Genotype
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The set of genes possessed by an individual organism.
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Homozygous
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Refers to an individual organism that possesses two identical alleles at a locus.
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Heterozygous
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Refers to an individual organism that possesses two different alleles at a locus.
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Phenotype
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Appearance or manifestation of a characteristic.
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Monohybrid Cross
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A cross between two individuals that differ in a single characteristic—more specifically, a cross between individuals that are homozygous for different alleles at the same locus (AA × aa); also refers to a cross between two individuals that are heterozygous for two alleles at a single locus (Aa × Aa).
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P (parental) Generation
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First set of parents in a genetic cross.
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F1 (filial 1) Generation
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Offspring of the initial parents (P) in a genetic cross.
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Reciprocal Crosses
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Crosses in which the phenotypes of the male and female parents are reversed. For example, in one cross, a tall male is crossed with a short female and, in the other cross, a short male is crossed with a tall female.
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F2 (filial 2) Generation
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Offspring of the F1 generation in a genetic cross; the third generation of a genetic cross.
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Dominant
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Refers to an allele or a phenotype that is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in a heterozygote phenotype
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Recessive
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Refers to an allele or phenotype that is expressed only when the recessive allele is present in two copies (homozygous). The recessive allele is not expressed in the heterozygote phenotype.
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Principle of Segregation (Mendel's First Law)
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Important principle of heredity discovered by Mendel that states that each diploid individual possesses two alleles at a locus and that these two alleles separate when gametes are formed, one allele going into each gamete.
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Concept of Dominance
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Principle of heredity discovered by Mendel stating that, when two different alleles are present in a genotype, only one allele may be expressed in the phenotype. The dominant allele is the allele that is expressed, and the recessive allele is the allele that is not expressed.
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Chromosome Theory of Heredity
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States that genes are located on chromosomes.
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Backcross
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Cross between an F1 individual and one of the parental (P) genotypes.
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Punnett Square
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Shorthand method of determining the outcome of a genetic cross. On a grid, the gametes of one parent are written along the upper edge and the gametes of the other parent are written along the left-hand edge. Within the cells of the grid, the alleles in the gametes are combined to form the genotypes of the offspring.
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Probability
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Likelihood of the occurrence of a particular event; more formally, the number of times that a particular event occurs divided by the number of all possible outcomes. Probability values range from 0 to 1.
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Multiplication Rule
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States that the probability of two or more independent events occurring together is calculated by multiplying the probabilities of each of the individual events.
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Addition Rule
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States that the probability of any of two or more mutually exclusive events occurring is calculated by adding the probabilities of the individual events.
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Testcross
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A cross between an individual with an unknown genotype and an individual with the homozygous recessive genotype.
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Wild Type
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The trait or allele that is most commonly found in natural (wild) populations.
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Dihybrid Cross
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A cross between two individuals that differ in two characteristics—more specifically, a cross between individuals that are homozygous for different alleles at the two loci (AA BB × aa bb); also refers to a cross between two individuals that are both heterozygous at two loci (Aa Bb × Aa Bb).
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Principle of Independent Assortment (Mendel's Second Law)
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Important principle of heredity discovered by Mendel that states that genes encoding different characteristics (genes at different loci) separate independently; applies only to genes located on different chromosomes or to genes far apart on the same chromosome.
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Goodness-of-Fit Chi-Square Test
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Statistical test used to evaluate how well a set of observed values fit the expected values. The probability associated with a calculated chi-square value is the probability that the differences between the observed and the expected values may be due to chance.
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