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Genes
instruction sets for biochemical, physical, behavioral traits
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Heredity
the passing of characteristics from parent to offspring through their genes
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Gregor Mendel
- learned about heredity by conducting experiments
- studied pea plants
- crossed true breeding purple flower plants with true breeding white flower plants
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True-Breeding
always produced offspring with the same variant of the trait as the parents
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Mendels Law of Segregation
- youve got two copies of each gene but only one copy in each sperm or egg
- a dominant trait masks the effect of a recessive trait
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Pattern of Inheritance
- Each parent puts into every sperm or egg it makes a single set of instructions (gene) for building the trait
- Offspring thus find themselves with two copies of the instructions for any trait (called alleles)
- The actual trait produced by an individual depends on the two copies of the gene that they inherit from their parents (homozygous and heterozygous)
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Phenotype and Genotype
- Phenotype: outward appearance of an individual
- Genotype: organisms genetic composition
- Not always possible to determine an indiviuals genotype from its phenotype
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Pedigree
- type of family tree
- help scientists, doctors, animal and plant breeders, and prospective parents determine: the genes that individuals carry, the genes that their offspring will likely carry
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incomplete dominance
a heterozygote displays a characteristic somewhere between the characteristics of the two homozygotes
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codominance
a heterzygote displays characteristics of both homozygotes
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Multiple Allelism
- occurs when there are three or more alleles for a gene within a population . An individual still inherits only two alleles - one from each parent
- Red blood cells: AA, AO, BB, BO, AB, OO (genotype) A, B, AB, O (phenotypes)
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Antigens
- chemicals on the surface of some cells
- they act as signposts that tell the immune system whether the cell belongs in the body
- antibodies are immune system molecules that attack cells with foreign antigens
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Polygenic Trait
trait that is influenced by many different genes
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Pleiotropyd
occurs when one gene influences multiple, different traits
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Phenylketonuria (PKU)
characterized by the inability of the body to utilize the essential amino acid phenylalanine
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