In a population of damselfish, the gene responsible for color pattern produces three distinct phenotypes: solid...

In a population of damselfish, the gene responsible for color pattern produces three distinct phenotypes: solid blue (AA), blue and yellow striped (Aa), and solid yellow (aa). The (Aa) damselfish are more conspicuous and so are predated at a higher rate (SAa =0.6). suppose you counted 4400 solid blue,v2400 blue and yellow striped, and 3200 solid yellow damselfish on a particular coral reef

(a) calculate the initial frequencies of the 3 genotypes and the 2 alleles.

(b) what would the allele frequency for the recessive allele (a) be among the breeding adults after one generation (what is q₁)?

(c) if you counted 1000 baby damselfish from among the offspring of the adults in part (b), assuming they mate randomly, how many of them would be blue and yellow striped?

(d) if this form of selection continued for many generations, how would what your great-grandchildren observe in the future compare with what you might observe today?

Solutions

Expert Solution

a) the Hardy-Weinberg principle applies to the individual gene with two alleles, a dominant allele, and a recessive allele. a population with such a gene can be described in terms of its genotype numbers-the number of individuals with each of the resulting genotypes-or in terms of genotype frequencies. the frequency of each genotype is the number of individuals in the population with that genotype divided by the total number of individuals in the population. the total genotype frequency is 1.

Genotypes	Number with these genotypes	genotype frequencies
AA	4400	0.44
Aa	2400	0.24
aa	3200	0.32
Total	10000	1.0

the frequency of an allele is defined as the total number of copies of that allele in the population divided by the total number of copies of all the alleles of the gene

the total number of dominant A allele in our population equals, the sum of

-the number of AA individuals times 2(the number of A alleles per individual) =4400*2=8800

-the number of Aa individuals times 1(the number of A alleles per individual) +2400

11200

the total number of all alleles of the gene equals 20000 which is 2 times the number of individuals in the population.

The frequency of the dominant A alleles in our population equals 11200/20000 equals 0.56

The total number of recessive a alleles in the population equals, the sum of

- the number of aa individuals times 2 =3200*2=6400

- the number of Aa individuals times 1 +2400

8800

total number of all alleles of the gene equals to 20000

so the frequency of the recessive "a" allele in our population equals 1.0-0.56=0.44(Hardy-Weinberg equation).

B. The Hardy-Weinberg principle predicts that allelic frequencies remain constant from one generation to next, or remain in EQUILIBRIUM, if you assume certain conditions such as 1. population is infinitely large,2. no selection occurs, 3. mating is random, 4. no migration, 5. no mutation

Allelic frequency of allele "a" in the initial population is 0.44, the allelic frequency in the next generation will remain 0.44.

C. 2400

The random mating model- the mating pairs have the same frequencies as if they were formed by random collisions between genotypes.

D. The random mating over generations maintains the level of genetic variation in a population.

gladiator answered 1 week ago

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