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Blending Theory of Inheritance-
organisms contribute equally offspring so that the offspring will have an intermediate appearance
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Gregor Mendel-
1860's, Australian monk, father of
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monohybrid Inheritance-
Cross of organisms that differ in 1 trait
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Parental generation-
(P) tall x short
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First filial generation-
(F1) tall x tall
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Second filial generation-
(F2) tall x short
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Mendel's Law of Segregation-
each organism contains 2 factors for each trait, and the factors segregate during the formation of gametes so that each gamete contains only one factor from each pair of factors. When fertilization occurs, the new organism will have 2 factors for each trait, 1 from each parent.
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Alleles-
alternate forms of a gene
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Dominant allele-
masks the expression of a recessive allele
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Recessive Allele-
expression is hidden by a dominant allele
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Gene Locus-
location on a chromosome where an allele occurs
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Homozygous-
organism has 2 identical alleles for a trait
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Heterozygous-
organism has 2 different alleles for trait
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Genotype-
the alleles an individual receives at fertilization
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Phenotype-
The physical appearance of an individual
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Punnett square-
a grid-like devicefor working simple genetic crosses
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Monohybrid Test Cross-
Determines whether an individual with the dominant phenotype is homozygotes or heterozygotes
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Dihybrid Test Cross-
- determines if an individual with the dominant phenotype is homozygotes or heterozygotes
- done by crossing the dominant with recessive
- if homozygous dominant, all offspring show the same
- if heterozygous, offspring will have a 1:1:1:1
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Pedigree Charts-
- show the pattern of inheritance
- constructed to predict whether a couple is likely to pass on genetic disorder
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Incomplete dominance-
- off spring show characteristics intermediateof the parents
- NOT the blending theory of inheritance because parantal phenotypes reappear in the F2 generation
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Phenotype- A
Genotype- AA, AO
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Codominance-
both alleles of a gene are equally expressed
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Polygenic Inheritance-
- One trait controlled by several pairs of alleles.
- Each dominant allele contributes in an equal and additive manner
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Human Polygenic traits-
height, skin color, behavior
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Human polygenic disorders-
cleft lip, cleft palate,club foot, high BP, cancer, diabetes
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Pleiotropy-
- a gene that affects more than one phenotypic trait
- Ex. Albinism-aa- cannot produce melanin
- Marfan syndrome-long lany, abnormal collegan
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What affects the phonotype?
enviroment
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X-linked recessive inheritance characteristics-
- More males than females are affected
- an affected son can have parents who have the normal phenotype.
- for a female to have the characteristic, her father must also have it. Her mother must have it or be a carrier,
- the characteristic often skips a generation from the grandfather to the grandson
- if a woman has the chracteristic, all of her sons will have it
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