Bio. 203 Lecture 3 and 4 RSA 1-26 -09

# Bio. 203 Lecture 3 and 4 RSA 1-26 -09 - Chromosomes...

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Walther Flemming Chromosomes contain the units of heredity

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Walter Sutton 1902 Sutton Bovery Hypothesis Chromosomes contain the units of heredity Mendel's particles parallel the behavior of chromosomes at meiosis 1913 Elinor Carothers heteromorphic chromosome pair in Grasshoper
Thomas Hunt Morgan 1910 Morgan noticed one fruit fly with a distinctive characteristic: white eyes instead of red. Red XXR X XXr white F 1 Red dominant F2 Females: XR XR , XR Xr red-eye female Xr X r white-eyed females F2 Males : XR Y red-eye male Xr Y white-eyed male

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1922 Alfred Blakeslee 12 stains each containing a different extra chromosomes and 12 different appearances. Jimsonweed
F 1  x F 1 F 2   Ratio 3:1 Dihybrid cross: F2 Ratios = 9:3::3:1

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Probability What is the chance that a given event will occur? what is the chance that a child, or a family of children, will have a given phenotype? Probability - expressed in numbers between 0 and 1. Probability = 0 means the event never happens probability = 1 means it always happens. The total probability of all possible event always sums to 1.
Chance deviation from an expected outcome is diminished by larger sample size .

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The Multiplication and Addition Rules The multiplication rule probability that two or more independent events will occur together is the product of their individual probabilities. The addition rule States that the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities
The Multiplication Rule States that the probability that two or more independent events will occur together is the product of their individual probabilities.

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Laws of probability Help Explain Genetic Events Genetic rations are most properly expressed as probabilities - 3/4 tall:1/4 dwarf. These values predict the out come of self fertilization of F1 for one pair of contrasting alleles. × Rr Segregation of alleles into eggs Rr Segregation of alleles into sperm R r r R R R R 1 2 1 2 1 2 1 4 1 4 1 4 1 4 1 2 r r R r r Sperm × Eggs
The rule of addition States that the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities

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Conditional Probability When one event depends on another, the likelihood of the desired outcome is the conditional probability. Example: In a monohybrid cross DD X dd. What is the probability that a tall plant is heterozygous? Pc = Pa/Pb Pa : p of heterozygous Pb: p of a plant being tall Pc= (1/2)/(3/4)=2/3
In a family of four children, what is the probability of having 2 boys and 2 girls? B1

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## This note was uploaded on 04/03/2009 for the course BIOLOGY 2203 taught by Professor Anthwal during the Spring '08 term at Temple.

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Bio. 203 Lecture 3 and 4 RSA 1-26 -09 - Chromosomes...

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