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Transcript of Ch 14: Mendel & the Gene Idea - dewhozitz.netdewhozitz.net/biolv04/14-Mendelgen.pdf · 3/10/15! 1!...
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Ch 14: Mendel & the Gene Idea
Optional but fun book
Johann Gregor Mendel the “Father of Genetics”
(Read his original paper at mendelweb.org)
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Methods of controlling pea genetics
Hand pollination (& emasculation)
Carl Correns Hugo de Vries Erich von Tschermak
The rediscoverers
Mendel’s discoveries and insights Q: Do alleles blend (& stay blended)? Q: Are traits/characters (things we now call genes) only found in one version?
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Q: Do both parents contribute equally to their offspring?
Q: How do these alleles, if different, interact?
dominant recessive
Q: Is there an equal chance of getting either of the 2 alleles a parent has? Mendel’s Law of Segregation
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Do genes sort independently (travel separately) of 1 another or sort together? Y - Mendel’s Law of Independent Assortment N - genetic linkage
Genetic terminology
Monohybrid cross: following one trait Punnett square ->
(parental)
(1st filial)
(2nd filial)
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Test cross (when you don’t know what the genotype is)
Dihybrid cross: following two traits simultaneously
Using rules of probability Multiplication/product rule
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Multiplication/product rule
Trihybrid cross PpYyRr x Ppyyrr Q: What fraction of the offspring from this cross will exhibit at least 2 recessives? Use the multiplication/product rule to find the combined probabilities for the allele pairs: Then use the addition/sum rule to combine these mutually exclusive events.
What Mendel didn’t know:
Incomplete dominance
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What Mendel didn’t know: Codominance Multiple Alleles
Just FYI (optional): Glycolipids and glycoproteins play a major role in signaling cell characteristics to the outside world. For example, A, B, O blood groups result from having different carbohydrate chains on the cell surface glycolipids and glycoproteins of red blood cells and other types of cells. Everyone has glycolipids and glycoproteins which have a particular type of carbohydrate chain which signals type O. People with type A also have glycolipids and glycoproteins which have an carbohydrate called N-acetylgalactosamine added to the basic type O carbohydrate chain. People with type B have an added galactose. Those with type AB have some glycolipids and glycoproteins with N-acetylgalactosamine added and other glycolipids and glycoproteins with galactose added.
http://www.bio.miami.edu/tom/courses/bil255/bil255goods/12_membrane.html
What Mendel didn’t know: Pleiotropic traits
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What Mendel didn’t know: Epistasis
B = black
b = brown (chocolate)
E = color produced
e = no color
What Mendel didn’t know: Polygenic traits
e.g.: skin color
What Mendel didn’t know: Environmental effects
e.g.: hydrangea color (soil pH)
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Human pedigree analysis
Recessively inherited traits: albinism
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Tay-Sachs
buildup of brain lipids
Sickle cell anemia
Dr. Michael Ain
(ped-ortho)
Dominantly inherited traits: achondroplasia
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Polydactyly
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Imaging: ultrasound
DNA testing: PGD (embryo) fetal cells in mother’s blood
Phenylketonuria
Neonatal testing
A few interesting human genetics stories http://mosaicscience.com/story/man-golden-blood http://www.archives.com/genealogy/family-heritage-blue-people.html