| (1) | gene | A gene is a unit that controls a specific hereditary trait.
As the development of genetics is becoming complicated, nowadays, the concepts of gene can be different under different circumstances. So, the definition of gene would be clarified in later pages.
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| (2) | allele | An allele is a factor of a gene. A gene can have more than 2 different alleles, but in an individual (diploid), a gene should have two alleles only.
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| (3) | dominance | When the individual carries two different alleles for a specific trait, only one can be expressed. The expressed one is said to be "dominance".
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| (4) | recessive | When an individual carries two different alleles for a specific trait, only one can be expressed. The one that cannot be expressed is said to be "recessive".
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| (5) | homozygote | If the two alleles of a specific trait of an individual are the same, the individual is said to be a homozygote in that trait.
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| (6) | heterozygote | If the two alleles of a specific trait of an individual are different, the individual is said to be a heterozygote in that trait.
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| (7) | genotype | The formula showing the combination of alleles of specific trait(s) is called the genotype of the individual.
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| (8) | phenotype | The description of the expression of specific trait(s) of a certain individual is said to be the phenotype of this individual.
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| (9) | true-bred | In an individual, if all traits on test are homozygous, then, the individual is said to be true-bred.
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| (10) | hybrid | In an individual, if any trait on test is heterozygous, then, the individual is said to be a hybrid.
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| (11) | wild type | According to the law of natural selection, the individual that can survive in the wild must be the fittest for survival. According to the theory of genetic shift, the allele that is the fittest for survival must get the dominant status. Therefore, all expression of the wild type individual must be dominant.
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| (12) | parent | At the beginning of the hereditary experiment, if both individuals are homozygous, then, these two individuals can be called "parent" in the experiment.
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| (13) | first filial generation F1 | The generation produced in the cross of parent is said to be the first filial generation F1.
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| (14) | second filial generation F2 | The generation produced in the cross of two F1 individuals is said to be the second filial generation F2.
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