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43 Cards in this Set
- Front
- Back
Unlinked genes
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Two genes having loci on different chromosomes
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Independent assortment
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Sorting of alleles during meiosis after which the gametes can end up with any combination of the maternal and paternal chromosomes; classes of gametes produced in equal frequency
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Linked genes
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Genes having loci on the same chromosome; physically "linked" to each other
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Dependent assortment
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Sorting of alleles during meiosis after which the gametes can end up with only certain combinations of maternal and paternal chromosomes because of linked genes
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Parental gametes
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Gametes produced from dependent assortment without recombination
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Heterozygous
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Individual in which the maternal and paternal alleles of a gene are different
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X chromosome
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Sex chromosome of which females have two and males have one
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Y chromosome
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Sex chromosomes of which males have one along with one X chromosome
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Heteromorphic pair
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Chromosomes such as the X and Y in males that are not homologous and usually differ in size
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Hemizygous
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Having one copy of each X- and Y-linked gene (males)
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Heterogametic
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Producing two types of gametes depending on sex chromosome content (male mammals)
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Homogametic
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Producing one type of gamete only containing X chromosomes (female mammals)
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Y-linked genes
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Present only in males; passed to all sons
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Holandric
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Inheritance confined to males caused by Y-linked genes
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Mendelian phenotypes
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Phentoypes controlled by a single gene
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Polygenic phenotypes
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Phenotypes controlled by multiple different genes acting together
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Homozygous
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Individuals with identical copies of each autosomal gene
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Dominant allele
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Determines the phenotypes in the heterozygote
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Recessive allele
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Has no effect on the phenotype in the heterozygote
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Null alleles
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Nonfunctional recessive alleles; the phenotype they cause is the result of no gene function
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Incomplete dominance
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A heterozygote's phenotype is intermediate between the phenotypes of the homozygotes
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Codominance
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A heterozygote shows the phenotypes of both alleles
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Pleiotropic
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Gene or allele that affects multiple phenotypes
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Temperature sensitive
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Codominant allele of a phenotype that is defined biochemically
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Lethals
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Null alleles of genes that are essential for survival; usually recessive
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Deleterious alleles (sublethals, semilethals)
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Cause a non-lethal disadvantageous condition; can be dominant, incompletely dominant, or recessive
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Incomplete penentrance
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Genotype that does not always cause the expected phenotype; can be the result of genetic background
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Variable expressivity
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Phenotype is present, but not constant (causes a characteristic that is variable)
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Genetic background
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All of the genes of the organism other than those obviously involved with one phenotype; affects the internal environment of an organism
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Dosage compensation
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Mechanism that ensures that males and females have the same amount of X chromosome activity, regardless of the number of X chromosomes
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Barr body
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An inactive X chromosome that appears as a darkly stained structure in the nucleus of the cell
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X inactivation
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Inactivation of all but one X chromosome in mammals
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Genetic mosaic
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"Patchwork" of phenotypes controlled by two chromosomes, such as X chromosomes in females
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Cell non-autonomous
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Phenotype controlled by an X-linked gene in one cell that affects all of the cells in the body
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Cell autonomous
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An X-linked gene that controls a phenotype restricted to the cell in which it was made; causes a "genetic mosaic"
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Non-disjunction
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Occurence in male meiosis during which both the X and Y chromosomes will go to the same pole or no poles at all, producing gametes with two sex chromosomes or none at all
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Epistasis
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Form of polygenic inheritance in which the genotype at one locus overrides or modifies the phenotype caused by another locus
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Additive inheritance
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Form of polygenic inheritance in which multiple genes control a phenotype, and each allele of each gene has an incremental affect on phenotype
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Phenocopy
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Phenotype that looks like a genetically-caused phenotype, but is really caused by the environment
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Familial
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Diseases that are genetically determined
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Idiopathic, sporadic
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Diseases that are environmentally induced
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Norm of reaction
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Range of the phenotype that can be produced from a single genotype, given the cariation in the environment
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Heritability
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The proportion of the phenotype that is caused by the genotype
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