Biology 106 Dr. Dudash

Study Questions Fall 1999

Study Questions Set #4 - Handed out February 15, 1999.

Due: In Lab the following week.

All answers MUST be TYPED unless mathematical computation is needed.

Use no more than 3/4 of a page of single spaced typed text.

Please answer the following questions:

1. In a population of 100 randomly mating individuals the frequency of individuals with black hair is 60, brown hair is 24, and blonde hair is 16.

a) How many copies of each allele are in the gene pool of this population for hair color? what is the distribution of alleles among phenotypes?

	individuals	B allele	b allele
black BB (p2)	60	120	0
brown Bb (2pq)	24	24	24
blond bb (q2)	16	0	32
TOTAL	100	144	56

b) What is the genotypic frequency of the black hair individuals in the population?

BB = p2 = 0.60= 60/100

c) What is the phenotypic frequency of brown hair individuals in the population?

Bb = 2pq = 0.24 = 24/100

d) Calculate p and q:

p = p2 + 1/2 2pq = 0.60 + 1/2 (.24) = 0.72

q = q2 + 1/2 2pq = 0.16 + 1/2 (.24) = 0.28

e) Is this population in Hardy-Weinberg equilibrium?

sqrt p squared + sqrt q squared does not equal 1.0 so the population is NOT in HWE.

2. A biology class censuses a field of spring wild flowers. They decide to census flower color of 100 randomly chosen individuals. They discover that 16 individuals have white flower petals and the remaining have purple flowers. Provide the following information on this population of plants.

a) What is the frequency of the albino genotype?

q squared = 0.16

b) What is the frequency of the allele that confers albinism (homozygous recessive state)?

q = 0.4

c) What is the frequency of allele conferring purple color?

p = 0.6

d) What is the frequency of the purple genotypes?

.36 + .48 = 0.84

e) Do you expect natural selection to remove the allele that confers albinism from this population?

NO, recessive allele is harbored in the heterozygote state. One needs to know if possessing white flowers is disadvantageous or advantageous in the population w/r to reproduction compared to purple flowered individuals.

3. Another biology class decided to census the frequency of tongue rollers in their class. They found that 22/200 individuals were not able to roll their tongue. We know that the ability to roll one's tongue is based on a 2 allele one locus system where tongue rolling is dominant, thus the students unable to roll their tongue are "rr". HINT: round to 2 decimal places.

a) What is the genotypic frequency of the students unable to roll their tongue?

q squared = 0.11; q = sq rt of 0.11 = 0.33 so p = 0.67

b) What are the genotypic frequencies of the folks able to roll their tongues?

freq.(RR) = p squared = 0.45 and freq.(Rr) = 2pq = 0.44

c) Is this population of students in Hardy-Weinberg equilibrium with regards to tongue rolling?

sqrt p squared + sqrt q squared = 1 so YES in HWE