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34 Cards in this Set
- Front
- Back
allele
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gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes
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autosomes
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any of the non-sex chromosomes
blending theory of inheritance hypothetical inheritance pattern in which parental traits are blended together in the offspring to produce an intermediate physical appearance
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codominance
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in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic
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continuous variation
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inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them
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dihybrid
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result of a cross between two true-breeding parents that express different traits for two characteristics
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discontinuous variation
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inheritance pattern in which traits are distinct and are transmitted independently of one another
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dominant
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trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait
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dominant lethal
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inheritance pattern in which an allele is lethal both in the homozygote and the heterozygote; this allele can only be transmitted if the lethality phenotype occurs after reproductive age
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epistasis
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antagonistic interaction between genes such that one gene masks or interferes with the expression of another
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F1
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first filial generation in a cross; the offspring of the parental generation
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F2
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second filial generation produced when F1 individuals are self-crossed or fertilized with each
other
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genotype
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underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism
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hemizygous
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presence of only one allele for a characteristic, as in X-linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant
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heterozygous
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having two different alleles for a given gene on the homologous chromosome
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homozygous
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having two identical alleles for a given gene on the homologous chromosome
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hybridization
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process of mating two individuals that differ with the goal of achieving a certain characteristic in their offspring
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incomplete dominance
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in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype
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law of dominance
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in a heterozygote, one trait will conceal the presence of another trait for the same characteristic
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law of independent assortment
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genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur
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law of segregation
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paired unit factors (i.e., genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors
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linkage
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phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together
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model system
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species or biological system used to study a specific biological phenomenon to be applied to other different species
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monohybrid
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result of a cross between two true-breeding parents that express different traits for only one characteristic
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P0
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parental generation in a cross
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phenotype
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observable traits expressed by an organism
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product rule
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probability of two independent events occurring simultaneously can be calculated by multiplying the individual probabilities of each event occurring alone
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Punnett square
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visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively, and the possible zygotic genotypes are recombined at each box in the grid
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recessive
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trait that appears “latent” or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive trait is expressed
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recessive lethal
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inheritance pattern in which an allele is only lethal in the homozygous form; the heterozygote may be normal or have some altered, non-lethal phenotype
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reciprocal cross
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paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross
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sex-linked
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any gene on a sex chromosome
sum rule probability of the occurrence of at least one of two mutually exclusive events is the sum of their individual probabilities
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test cross
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cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait
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trait
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variation in the physical appearance of a heritable characteristic
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X-linked
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gene present on the X, but not the Y chromosome
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