Presentation on theme: " The relationship of an allele to the total number of alleles in a gene pool for a trait. Expressed as a percent Allele frequency can be used to."— Presentation transcript:
The relationship of an allele to the total number of alleles in a gene pool for a trait. Expressed as a percent Allele frequency can be used to determine the diversity of a population. The closer the percentages are to each other, the more diverse a population is,
In a large pond a survey was taken from DNA sample of a species of frog. The following genotypes were observed: GG 80 frogs (Green color) Gg 40 frogs (Green color) Gg 20 frogs (Brown color) What is the allele frequency for both variations?
First, calculate how many total alleles are in this population. 140 frogs x 2 = 280 Second, calculate how many of each allele. GG 80 frogs x 2 = 160 G Gg 40 frogs = 40 G + 40 g gg 20 frogs x 2 = 40 g 160 + 40 = 200 G 40 + 40 = 80 g
Last, divide each allele total by the total number of alleles and covert to percent. For G: 200/280 = 0.71 = 70 % * For g: 80/280 = 0.28 = 30 % * * Figures were rounded.
Short and tall plants were analyzed in a garden and these results were found. What is the allele frequency of each type allele. Tall is dominant over short plants. TT 120 plants Tt 120 plants tt 80 plants Round off the percents to whole numbers.
TT 120 plants 120 x 2 = 240 T’s Tt 120 plants 120 T’s and 120 t’s tt 80 plants 80 x 2 = 160 t’s Total Alleles = 640 alleles Total T’s = 360 alleles 360/640 = 0.6 = 60% Total t’s = 280 alleles 280/640 = 0.4 = 40%
Red eyes (R) in fruit flies is dominant over white eyes (rr). In a population of 720 it was found that 30 % carried the recessive allele. How many carried the recessive allele? How many carried the dominant allele?
The population was 720, so we know the toal number of alleles is 1,440. We know that 30 percent carried the recessive allele so the dominant percentage was 70. 30 % of 1,440 is 432 70% of 1,440 is 1,008
It is more common to want to know the genotype frequencies in a population. We may want to know how many homozygous dominant or heterozgous genotypes there are. If we know the frequencies of the alleles, we can find the genotype frequencies.
These two men developed a mathematical formula to determine if evolution has occurred in a population. If gene frequency changes significantly, then evolution has take place.
A population is in equilibrium if: (No evolution is occurring) 1. No mutations occur. 2. No migration in or out of population occurs (gene flow) 3. Mating must be random 4. the population must be very large. 5. No natural selection can is occurring.
p2 + 2pq + q2 = 1 and p + q = 1 p = frequency of the dominant allele in the population q = frequency of the recessive allele in the population p2 = percentage of homozygous dominant individuals q2 = percentage of homozygous recessive individuals 2pq = percentage of heterozygous individuals
A population is sampled in which it was found that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following: 1. The frequency of the “a” allele. 2. The frequency of the “ A” allele 3. The frequency of genotype “AA” 4. The frequency of genotype “Aa” 5. The frequency of genotype “aa” Given=36%
The frequency of the “a” allele. The frequency of aa is 36%, which means that q2 = 0.36, by definition. If q2 = 0.36, then q = 0.6, again by definition. Since q equals the frequency of the a allele, then the frequency is 60%
The frequency of the “ A” allele. Since q = 0.6, and p + q = 1, then p = 0.4. Tthe frequency of A is by definition equal to p, so the answer is 40%.
The frequency of genotype “AA” The frequency of AA is equal to p2. So, using the information above, the frequency of AA is 16% (i.e. p2 is 0.4 x 0.4 = 0.16)
The frequency of genotype “Aa” The frequency of Aa is equal to 2pq. So, using the information above, frequency of Aa is 48% (2pq = 2 x 0.4 x 0.6 = 0.48).