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BIOL 2200 Lecture Notes - Lecture 4: Punnett Square, Gene Pool, Panmixia

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amberrabbit135
25 Jan 2017
School
University of Virginia
Department
Biology
Course
BIOL 2200
Professor
Jessamyn Manson

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Document Summary

Mendel observed 3:1 patterns of inheritance of phenotypic traits. Recessive allele is masked in the phenotype. We need to know about the genes at the population level. Population = group of individuals of the same species that live in the same area and interbreed, leaving viable offspring. Gene pool = all copies of all alleles at every locus for all individuals in the population. If alleles are transmitted by meiosis and random mating, frequencies do not change over time. Frequencies of alleles a1 and a2, is given by p and q, respectively. P +q must always add up to one. P^2 + 2pq + q^2 = 1. One way to calculate allelic frequency is to add up the percent of p^2 and half of the percent of 2pq. Can also calculate genotypic frequency using a punnett square. In hardy-weinberg equilibrium there is no change in allelic frequency. Mn codes for a protein on the surface of rbcs.

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Related Questions

Q1. Which of the following statements is true about the disease Kuru?
Kuru is caused by a virus, which is contracted by eating human brain material.
Kuru is caused by a prion (PrP), which is contracted by eating human brain material.
Kuru is caused by a recessive allele for PrP; if a person has two copies, he or she will develop Kuru.
Kuru is caused by a dominant allele for PrP; if a person has two copies, he or she will develop Kuru.
Kuru is caused by having one copy of the dominant allele and one copy of the recessive allele for PrP.

Q2. True or false: One can calculate the frequency of alleles in a population if the genotypes of the members of the population are known.

True False

Q3. The Hardy-Weinberg equation is p2 + 2pq + q2. In this equation, q2 stands for the frequency of ____________ in a population.

The recessive allele O

ne of the homozygous genotypes

The dominant allele

Heterozygous genotype


Q4. Which of the following descriptions best fits the relationship between the terms gene, allele, locus, and chromosome?

Alleles are different forms of a gene, which can be found at a locus on a chromosome.

Genes are made up of chromosomes, which can be found at a locus on an allele.

Chromosomes are different forms of a gene, which can be found at an allele on a locus.

A locus is made up of alleles, which can be found at a gene on a chromosome.

Q5. Mead and his colleagues proposed a hypothesis for the apparent heterozygote advantage for the PrP locus. What did they suggest as the basis for the high presence of both alleles?
History of cannibalism.
Protection from malaria.
Protection against plague.
They did not propose a heterozygotic advantage for the PrP locus.

Q7. A frog population has two alleles for skin color at the following relative frequencies: Allele SC1= 0.8, Allele SC2 = 0.2. Allele SC2 is:
Dominant
Recessive
Co-dominant
Impossible to determine dominance from the information given.


Q8. A bird population has two alleles for feather color at the following relative frequencies: Allele FC1 = 0.5, Allele FC2 = 0.5. Allele FC1 is:
Dominant
Recessive
Co-dominant
Impossible to determine dominance from the information given.

Q9. Use the following information for both questions 9 and 10: You encounter a few populations of millipedes with variation in skin color. Genotype can be inferred from coloration: CC millipedes are black, Cc millipedes are brown, and cc millipedes are yellow. [You can launch a calculator byclicking here.]

If one millipede population has 60 black individuals, 20 brown individuals, and 20 yellow individuals, what is the relative frequency of allele C in that population?

0.5
0.6
0.7
0.8
Impossible to calculate from the information given.

Q10. If another millipede population's allele frequencies are 0.5 for C and 0.5 for c, what is the expected frequency of the cc genotype in the population, if the population is in Hardy-Weinberg equilibrium?
0.125
0.25
0.5
1.0
Impossible to calculate from the information given.

Q1. What are alleles?Different forms of the same gene.Different genes.The different characteristics of an organism.Genes found only in humans.Q2. If you add up the frequency of homozygotes + the frequency of heterozygotes for one gene (i.e. at one locus) in a population, what number do you get?Q3. People who are heterozygous for the sickle-cell allele:Are susceptible to malaria but not sickle-cell anemia.Are susceptible to sickle-cell anemia but not malaria.Are not susceptible to either sickle-cell anemia or malaria.Are susceptible to both sickle-cecell anemia and malaria.Q4. In the case study in this lab, which genotype is represented by "2pq" in the Hardy-Weinberg equation?Homozygous HbAHomozygous HbSHeterozygous HbA/HbSNo specific genotypeQ5. Suppose that, in an isolated village, the proportion of individuals that have sickle-cell anemia is 0.1 (or 1 of every 10 people). What proportion of the population should be sickle-cell carriers, according to Hardy-Weinberg expectations?Q6. When you simulated the elimination of malaria at the beginning of the lab, once the allele frequencies stabilized, what was the frequency of the HbA allele?Q7. When you investigated regional differences, what was the frequency (over many generations) of the HbS allele in the village in the "slightly wet" part of Africa?Q8. What is the number of deaths due to sickle-cell anemia in a region without mosquitoes expected to be?Very lowVery highModerateRelated to the frequency of malaria allelesQ9. As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time?Because natural selection changes all allele frequencies in populations over time.Because genetic drift causes random fluctuations of allele frequencies in populations.Because diseases will eliminate some of the alleles, generating fluctuations in their frequencies.Because allele frequencies fluctuate before the alleles eventually become fixed.Q10. Imagine a huge population with a gene that has ten functionally equivalent, neutral alleles. A small but genetically representative group of individuals from the big population is transported to an island, forming a small population. Which of the statements below best describes what will likely happen over time, and why?Because natural selection doesn't act on neutral alleles, the frequencies in the two populations should remain the same over time.Genetic drift will cause one allele to first become fixed in the island population, and later to become fixed in the original, large population.Genetic drift will result in the allele frequencies of the two populations diverging over time, with alleles being lost sooner in the island population.The allele frequencies of the two populations will change similarly due to a combination of genetic drift natural selection.

1 A) Cystic Fibrosis is an autosomal recessive disease, 1 out of every 2500 individuals of Caucasian descent in the US have cystic fibrosis. What frequency of cystic fibrosis carriers would you expect in the Caucasian population of the US under Hardy Weinberg Equilibrium? Show your work. (1 pt)

1 B) You know that penguin tuxedo color is a classic Mendelian single-gene trait, the allele for black and white tux coloring (T) is dominant over gray and white tux coloring (t). In a population of penguins, there are 400 black and white tuxedoed penguins and 200 gray and white tuxedoed penguins.

(i) Which observed genotypic or allelic frequencies can be calculated from this scenario without assuming Hardy Weinberg Equilibrium? (1.5 pt)

(ii) In one to two sentences, explain why differences may arise between observed and expected genotype frequencies. (1 pt)

1 C) You are studying inheritance of external keratin features in a dinosaur. Analysis has found that the presence of feathers is due to codominance between the AS (scales) and AH (horns) alleles. In one generation of a population you find 78 scaled dinosaurs, 76 feathered dinosaurs, and 64 horned dinosaurs.

(i) What are the observed allele frequencies of AS and AH ? Use p for the frequency of AS and q for the frequency of AH . Show your work. (1.5 pt)

(ii) What are the observed genotypic frequencies? Show your work. (1 pt)

(iii) Given the allelic frequencies calculated above, what are the expected number of scaled, feathered, and horned dinosaurs in a population of the same size (218) under Hardy Weinberg Equilibrium? Show your work. (1.5 pt)

(iv) Use a chi-square test to examine whether the gene you are studying is under Hardy Weinberg Equilibrium in this population. Show your work. Do you accept or reject the null hypothesis? (2 pts)