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19 Cards in this Set
- Front
- Back
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Gene |
- unit of heredity that contributes to the characteristics or traits of an organism - composed of organized sequences of DNA |
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Locus |
the physical location of a gene on a chromosome |
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Allele |
a variant form of a gene |
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Homozygous |
an individual with 2 identical copies of an allele |
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Heterozygous |
an individual with 2 different alleles of the same gene |
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Genotype |
the genetic composition of an individual |
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Phenotype |
the characteristics of an organism that are the result of the expression of its genes |
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Dominant |
describes the displayed trait in a heterozygote |
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Recessive |
describes the trait that is masked by the presence of a dominant trait |
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Gregor Mendel |
- born 1822 - Austrian Empire (now Czech Republic) - joined the monastery at age 21 - historic studies on pea plants in monastery garden |
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Mendel's 1st Law of Inheritance (Law of Segregation) |
1) there are alternative versions of genes (alleles) that account for variation in traits 2) each organism contains 2 alleles for each trait; 1 allele was inherited from each parent 3) the 2 alleles for each trait segregated during gamete production (meiosis) |
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Mendel's 2nd Law of Inheritance (Law of Independent Assortment) |
- alleles of different genes assort independently of each other during gamete formation - independent assortment occurs during anaphase of meiosis 1 -use a 2-factor or "dihybrid" cross |
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Incomplete Dominance |
heterozygote has a phenotype that is intermediate to the phenotype of the dominant and recessive homozygotes ex: red flower+white flower= pink flower |
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Codominance |
heterozygote expressed both alleles simultaneously ex: red cow+white cow= roan cow |
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Sex-linked |
traits are determined by alleles located on the sex chromosomes ex: gene for color blindness located on the X chromosome only |
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Multiple Alleles |
more than 2 alleles can occupy a locus ex: ABO blood group system |
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Sex-influenced |
allele is recessive in one sex and dominant in the other ex: winglessness in fruit flies |
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Monohybrid Inheritance |
- inheritance of a single characteristic - forms are usually controlled by the dominant allele in one gene - clearly demonstrated in cases of direct inheritance |
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Punnett Square |
useful way to estimate the possible zygotes produced given certain gametes |
