Genetics Study Questions
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Trait
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Characteristic that is inherited; can be either dominant or recessive.
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P Generation
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The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance; P stands for \"parental.\"
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F1 generation
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The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross. First generation
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F2 generation
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The offspring resulting from interbreeding (or self-pollination) of the hybrid FF1 generation.
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The Law of Segregation
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Mendel's first law, stating that the two alleles in a pair segregate (separate from each other) into different gametes during gamete formation.
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Allele
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different types of the alternative versions of a gene that may produce distinguishable phenotypic effects are called
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Dominant Allele
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An allele that is fully expressed in the phenotype of a heterozygote. Only need 1 copy of dominant allele to show dominant trait.
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Recessive Allele
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An allele whose phenotypic effect is not observed in a heterozygote - it is \"masked\" or hidden.
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Genotype
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The genetic makeup, or set of alleles, of an organism. (Ex: PP, Pp or pp)
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Phenotype
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The EXPRESSED/observable physical and physiological traits of an organism, which are determined by its genetic makeup.
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Punnett Square
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A diagram used in the study of inheritance to show the predicted genotypic results of random fertilization in genetic crosses between individuals of known genotype.
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Homozygous
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Having two identical alleles for a given gene.
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Heterozygous
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Having two different alleles for a given gene.
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The Law of Independent Assortment
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Mendel's second law, stating that each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes.
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Dihybrid Cross
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A cross between two organisms that are each heterozygous for both of the characters being followed (or the self-pollination of a plant that is heterozygous for both characters).
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Incomplete Dominance
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The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.
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Codominance
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The situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways.
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Multiple Alleles
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Three or more forms of a gene that code for a single trait. example is blood type
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Sex-Linked Traits
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Traits controlled by genes located on sex chromosomes. If it is an X-linked trait (most common), the Y chromosome will be empty on the Punnett Square. If it is a Y-linked trait, the X chromosome will be empty on the Punnett square. Common sex-linked traits are male pattern baldness, colorblindness and hemophilia in humans and red/white eyes in fruit flies.
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Sex linked Chromosomes
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The 23rd pair of chromosomes in humans that determine the sex (or gender) of the individual. Women are XX and Men are XY.
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Polygenic
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Traits that are controlled by more than one gene, ex: skin color and hair color.
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Pedigree
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A genetic tool that looks at the history of a genetic disorder in a family.
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FOIL method
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Method of identifying the gametes possible for a dihybrid square. F - first set, O = outer set, I = inner set, L = last set.
