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24 Cards in this Set
- Front
- Back
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Gene
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a unit of hereditary information located on a chromosome; a region of the DNA that produces an RNA molecule.
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alleles
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alternative forms of a gene (differ in their nucleotide sequences)
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Genotype
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the genetic make up of an individual.
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phenotype
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the appearance of an individual; it is the expression of the genotype. The phenotype can be influenced by the environment.
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homozygous
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the two copies of a gene have the same allele (in a diploid organism there are two copies of each chromosome so two copies of each gene)
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heterozygous
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the two copies of a gene have different alleles (in a diploid organism)
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dominant (complete)
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an allele that is seen in the phenotype (expressed) when only a single copy is present
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Recessive
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an allele that is expressed only when both allels at a gene are the same (homozygous)
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dominan (incomplete)
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no allele is completely dominant; inviduals with two different alleles (heterozygous) have an intermediate phenotype
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codominant
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an invidiual with two different alleles (heterozygous) both allels are expressed in the phenotype
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epistasis
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a character is controlled by more than one gene and the genes act in a specific order, so the expression of the second gene is dependent on the expression of the first gene.
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segregation
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when homologous chromosomes separate at Anaphase I of Meiosis, the allels at a gene on that chromosome pair are segregated (separated) into different gametes.
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independent assortment
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alleles at one gene segregate independently from alleles at a second gene, on another chromosome. This is due to the random distribution of homologous chromosome pairs during Meiosis I.
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Pleiotropy
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a single gene has an affect on multiple characters.
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polygenic
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a character that is controlled by more than one gene. The trait will show a continuous distribution of phenotypes because each gene has a small additive affect ont he character.
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quantitative trait
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a character that shows continuous variation of phenotypes in a population (e.g. skin color, height).
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heritability
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the amount of variation in a character that is due to genetic differences (versus environmental differences)
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variance
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the amount of variation in a population for a particular character
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species
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a group of interbreeding populations that can produce fertile offspring and is reproductively isolated from other groups (species)
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sex-linkage
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when a gene is carried on a sex chromosome, the genotype of the individual will depend upon the sex of the individual
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hemizygous
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in the sex that has two different sex chromosomes (males in humans with an X chromosome and Y chromosome) an individual will have just one allele for a gene that is on one of the sex chromosomes because they have only one copy of that chromosome. therefore, that allele always will be expressed.
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gene poll
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genetic variation present in the genomes of an interbreeding group
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monomorphic
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only one form exists. Example - all individuals in a population are genotype aa
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polymorphic
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more than one form exists. example, individuals in a population can have AA, Aa, or aa genotypes.
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