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Population Genetics (allele frequencies and Hardy- Weinberg equilibrium) January 2009.

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Presentation on theme: "Population Genetics (allele frequencies and Hardy- Weinberg equilibrium) January 2009."— Presentation transcript:

1 Population Genetics (allele frequencies and Hardy- Weinberg equilibrium) January 2009

2 In a plant population, Frequency of allele A = 0.8 Frequency of allele a = 0.2 What might be the probability that any given pollen produced by these trees has the ‘A’ allele? A.0.8 B.0.4 C.0.2 D.0.1 E.Not enough information

3 Tongue rolling R = ability to roll tongue r = cannot roll tongue In a population of 100RR, 100Rr and 100rr What is the frequency of allele R? A. 1.0 B C. 0.5 D. 0.33

4 heterozygous red chuzzels Aa 48 homozygous red chuzzels AA 16 homozygous green chuzzles aa 36 What is the frequency of allele A? A B. 0.4 C. 0.6 D E Here is a population of chuzzels:

5 Early onset or infantile Tay-Sachs disease causes nerve cells deteriorate and then eventually die. The disease is inherited in an autosomal recessive manner. In a French Canadian community 9% (0.09) of the population has infantile Tay-Sachs. What is the chance that a man with no family information on the disease is a carrier (Aa) ? A. 4.5% B. 10.5% C. 15.5% D. 34% E. 42%

6 Cohen Syndrome has several characteristics such as obesity, mental retardation, and facial abnormalities. The disease is inherited in an autosomal recessive manner. In an Old Order Amish community 4% (0.04) of the population has Cohen Syndrome. If there is no information about whether this disease runs in the family, what is the chance that a disease free man is NOT a carrier (AA)? A.64% B.32% C.10% D.4% E.2%

7 A chuzzle populations contains 640 red chuzzels and 320 green chuzzles. Chuzzles are not choosy about their mates. Either color will mate with the other at equal frequencies. When red chuzzles mate all the pups are red. When red and green chuzzles mate some pups are red and some are green. There is no advantage (for mating or survival) based on color. Which trait is dominant? A) red B) green Chuzzle Population

8 You want to make some predictions about the chuzzle population. Will there be the same percent of red and green chuzzles in the next generation? A) yes B) no Chuzzle Population

9 Consider a punnett square looking at the population of chuzzles. homozygous red chuzzels AA heterozygous red chuzzels Aa heterozygous red chuzzels Aa homozygous green chuzzles aa 36% Now, let’s consider the gametes: Which gametes produced which offspring? a A A a What is the probability of creating an aa gamete? 36% or.36 What is the probability of getting an ‘a’ in a gamete? A).5 C).36 B).25 D).6

10 Consider a punnett square looking at the population of chuzzles. homozygous red chuzzels AA heterozygous red chuzzels Aa heterozygous red chuzzels Aa homozygous green chuzzles aa 36% a A A a.6 q =.6 = ‘a’ frequency What is the frequency of the ‘A’ allele? A).9 C).6 B).8 D).4 q q

11 Consider a punnett square looking at the population of chuzzles. homozygous red chuzzels AA heterozygous red chuzzels Aa heterozygous red chuzzels Aa homozygous green chuzzles aa 36% a A A a.6 p + q = 1 (a frequency) + (A frequency) = 1.4 What is the frequency of the AA genotype? (probability of being AA)? A).16 C).25 B).4 D).64 q q p p

12 Consider a punnett square looking at the population of chuzzles. homozygous red chuzzels AA heterozygous red chuzzels Aa heterozygous red chuzzels Aa homozygous green chuzzles aa 36% a A A a.6 p + q = 1 (a allele frequency) + (A allele frequency) = % p^2 = AA genotype frequency =.4 X.4 =.16 q^2 = aa genotype frequency =.6 X.6 =.36 What is the frequency of the Aa genotype? A) pq C)p^2 X q^2 B) 2 pq D)p^2 + q^2 p^2 q^2 q p pq

13 Some Questions: A man comes from a family with cystic fibrosis (CF). He has a brother with the disease, but he and his parents are not affected. The man’s wife comes from a family with no history of CF. Her probability of being a carrier of this recessive trait is the same as the rest of the population wherein 1 in 2500 births are infants with CF. 1.What is his probability of being a carrier (solved using Mendelian genetics)? A B C. 0.5 D E. 0.75

14 Some Questions: A man comes from a family with cystic fibrosis (CF). He has a brother with the disease, but he and his parents are not affected. The man’s wife comes from a family with no history of CF. Her probability of being a carrier of this recessive trait is the same as the rest of the population wherein 1 in 2500 births are infants with CF. 2. What is her probability of being a carrier (solved using Hardy-Weinberg law)? A B C D E

15 Some Questions: A man comes from a family with cystic fibrosis (CF). He has a brother with the disease, but he and his parents are not affected. The man’s wife comes from a family with no history of CF. Her probability of being a carrier of this recessive trait is the same as the rest of the population wherein 1 in 2500 births are infants with CF. 3.What is the probability that they will have a child with CF? A.0.66 B C D


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