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Lecture 2

BICD 100 Lecture Notes - Lecture 2: Chi-Squared Distribution, Mendelian Inheritance, Punnett SquarePremium

2 pages109 viewsWinter 2019

Department
Biol/Genetics,Cellular & Develop
Course Code
BICD 100
Professor
Deborah Yelon
Lecture
2

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Following two traits at once.
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Crossed yellow and round peas with green and wrinkled peas
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F1 is all round and yellow peas
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Now we can get new combinations like yellow and wrinkled and green and round
F2 self-fertilized generation gets 9/16 y/r, 2/16 y/w, 3/16 g/r, and 1/16 g/w.
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Each postulate has its exceptions so is not necessarily always true
Independent assortment
Mendel's 4th postulate
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O
GW
Gw
gW
gw
GW
GGWW
GGWw
GgWW
GgWw
Gw
GGWw
GGww
GgWW
Ggww
gW
GgWW
GgWw
ggWW
ggWw
gw
GgWw
Ggww
ggWw
Ggww
Now we can see the 9:3:3:1 ratio present with a heterozygous dihybrid cross
Draw a Punnett square of a GgWw xGgWw dihybrid cross
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The above ratio is phenotypic but the genotypic ratio is more complicated
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When two independent events occur simultaneously, the combined probability of the 2
outcomes is equal to the product of their individual probabilities. p(A and B) = p(A)*p(B)
Product law of probabilities
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Dihybrid cross:
Taking real-life data and deciding if it fits your genetic hypothesis
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Chi-square analysis evaluates the influence of chance on data
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Are they significantly different
X^2= sigma(O-E)^2/E
Statistical test to check your experimental results against expected ratios
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Null hypothesis: any differences between expected values and observed values are likely to be due
to chance
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Alternate hypothesis: the differences between expected and observed values are significant and
unlikely
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Chi-square analysis
State the null hypothesis
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Calculate expected numbers of progeny
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Use formula to calculate chi-square value
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Use table to translate chi-square into p value
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Draw conclusion about hypothesis
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Five steps of chi
Low p value means that the difference between your observe3d results and the expected
results is unlikely to be due to chance
P value less than 0.05 means you can reject the null hypothesis
Probability that your results are due to chance
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Meaning of a p value
(2) More on Mendelian Genetics
Thursday, January 10, 2019
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