Transcript q 2 - cloudfront.net

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Mini-Poster Symposium
Peppered moth
evolution
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gene pool
variation
phenotype
differential reporduction
survival
advantage
environment
allele
Game
http://www.techapps.net/int
eractives/pepperMoths.swf
Cockroach population Evolving?
1)
Pick up a whiteboard and marker. Split it in half
2)
Draw up a population of cockroaches. 5 dotted, 5 clear. D is the dotted allele and a is
the clear allele.
3)
On one half put all the cockroaches. Next to each cockroach put the genotype: AA, Aa
or aa. THESE ARE INDIVIDUALS. Yell checkpoint
4)
On the other side label gene pool just put alleles individually. THESE ARE ALLELE
FREQUENCIES
How many A? Total A/Total
How many a? Total a/Total
What do these symbols mean?
• p2
• q2
• 2pq
•p
•q
Using Hardy-Weinberg equation
population:
100 cats
84 black, 16 white
How many of each
genotype?
p2=.36
BB
q2 (bb): 16/100 = .16
q (b): √.16 = 0.4
p (B): 1 - 0.4 = 0.6
2pq=.48
Bb
q2=.16
bb
What assume
Must
are the population
genotype frequencies?
is in H-W equilibrium!
Hardy-Weinberg Equation
p=frequency of one allele (A);
q=frequency of the other allele (a);
p+q=1.0
(p=1-q & q=1-p)
• p2=frequency of AA genotype; 2pq=frequency of Aa genotype;
q2=frequency of aa genotype;
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frequencies of all individuals must add to 1 (100%), so:
p2 + 2pq + q2 = 1
G.H. Hardy
mathematician
W. Weinberg
physician
Hardy Problem
• Calculate q2 Count the individuals that are homozygous recessive in the illustration
above. Black is recessive to pink. Calculate the percent of the total population they
represent. This is q2.
Q2=4/16=0.25
Calculate q
q=0.5
p + q = l. You know q, so what is p, the frequency of the dominant allele?
P=0.5
Find 2pq
2pq = 2(0.5) (0.5) = 0.5 , so 50% of the population is heterozygous.
• Bozemanscience
Video on Hardy-Weinberg
Hardy-Weinberg=NO EVOLUTION
• To see what forces lead to evolutionary change, we must examine the
circumstances in which the Hardy-Weinberg law may fail to apply.
There are five:
• mutation
• gene flow
• genetic drift
• nonrandom mating
• natural selection
5 Agents of evolutionary change
Gene Flow
Genetic Drift
Mutation
Non-random mating
Selection
Problem 1
• In a certain population of 1000 fruit flies, 640 have red eyes while the
remainder have sepia eyes. The sepia eye trait is recessive to red
eyes. How many individuals would you expect to be homozygous for
red eye color?
• Hint: The first step is always to calculate q2! Start by determining the
number of fruit flies that are homozygous recessive. If you need help
doing the calculation, look back at the Hardy-Weinberg equation.
Solve the problem below
5 Agents of evolutionary change
Gene Flow
Genetic Drift
Mutation
Non-random mating
Selection
Problem 2
• The Hardy-Weinberg equation is useful for
predicting the percent of a human population
that may be heterozygous carriers of recessive
alleles for certain genetic diseases.
Phenylketonuria (PKU) is a human metabolic
disorder that results in mental retardation if it
is untreated in infancy. In the United States,
one out of approximately 10,000 babies is
born with the disorder.
• Approximately what percent of the population
are heterozygous carriers of the recessive PKU
allele?
Natural selection NOT in Hardy-Weinberg
Fitness: contribution an individual makes to the gene
pool of the next generation
3 types:
• A. Directional
• B. Diversifying
• C. Stabilizing