apologia biology module 8 study guide – Flashcards
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true breeding
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If an organism has a certain characteristic that is always passed on to its offspring we say that this organism is bred true with respect to that characteristic
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allele
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one of a pair of genes that occupies the same position on homologous chromosomes
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genotype
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two-letter set that represents the alleles an organism possesses for a certain trait
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phenotype
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the observable expression of an organism's gene
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homozygous genotype
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a genotype in which both alleles are identical
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heterozygous genotype
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a genotype with two different alleles
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dominant allele
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an allele that will determine phenotype if just one is present in the genotype
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recessive allele
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an allele that will not determine the phenotype unless the genotype is homozygous in that allele
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pedigree
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a diagram that follows a particular phenotype through several generations
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monohybrid cross
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a cross between two individuals, concentrating on only one definable trait
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dihybrid cross
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a cross between two individuals, concentrating on two definable traits
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autosomes
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chromosomes that do not determine the sex of an individual
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sex chromosomes
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chromosomes that determine the sex of an indevidual
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antigen
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a protein that, when introduced in the blood, triggers the production of an antibody
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autosomal inheritance
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inheritance of a genetic trait not on a sex chromosome
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genetic disease carrier
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a person who is heterozygous in a recessive genetic dissorder
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sex-linked inheritance
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inheritance of a genetic trait located on sex chromosomes
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mutation
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a radical chemical change in one or more alleles
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change in chromosome structure
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a situation in which a chromosome looses or gains genes during meiosis
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change in chromosome number
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a situation in which abnormal cellular events in meiosis lead to either none of a particular chromosome in the gamete or more than one chromosome in the gamete
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Mendel's principles of genetics
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1. the traits of an organism are determined by its genes 2. each organism has two alleles that make up the genotype for a given trait 3. in sexual reproduction each parent contributes only one of its alleles to the offspring 4. in each genotype there is a dominant allele. if it exists in an organism, the phenotype is determined by that allele
