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Example Question #6 : Population Genetics And Hardy Weinberg
Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma.
Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts.
She sets up the following experiment:
As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.
You are conducting a study of an isolated tribe in New Guinea, and you find that there is widespread resistance to cryptosporidium infection. Upon historical investigation, you find that the population you were studying all derived from a single group of four people that landed on the island 2000 years ago. Which phenomenon is most likely responsible for the observations of cryptosporidum resistance?
Genetic bottleneck
Founder effect
Penetrance
Pleiotropy
Balanced heterozygosity
Founder effect
The founder effect is the abnormal abundance of an allele in a population derived from a small initial population. If, by chance, the initial population had an abnormal abundance of a certain allele, this abnormality will generally persist for future generations.
Example Question #7 : Population Genetics And Hardy Weinberg
Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma.
Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts.
She sets up the following experiment:
As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.
You are conducting a study of an isolated tribe in New Guinea, and you find that there is widespread resistance to cryptosporidium infection. You determine that the population is in Hardy-Weinberg equilibrium. Which of the following is true of this population?
I. There is random mating
II. There is no immigration or emigration
III. There is a constant rate of mutation
I only
I and II
III only
I and III
I, II, and III
I and II
Hardy-Weinberg equilibrium states that there is random mating, no immigration/emigration, and that there are no mutations.
Example Question #1 : Population Genetics And Hardy Weinberg
Which of these populations could meet the criteria required for Hardy-Weinberg equilibrium?
A population of over 50,000 elephants routinely travels from the western region of Africa to a more central region to deal with seasonal food supply fluctuations.
A group of about 40 swans displays random mating and does not migrate to areas with other swan populations.
Finches randomly mate on a small island in the Caribbean. These birds eat hard-shelled seeds, so finches with short, strong beaks experience directional selection.
A population of about 100,000 wild cats mate randomly and stay in the same area. Their mutation rate is negligible and their environment contains no factors that select for specific traits.
A very large group of people has a near-zero mutation rate, no migration, and a tendency to marry their first cousins.
A population of about 100,000 wild cats mate randomly and stay in the same area. Their mutation rate is negligible and their environment contains no factors that select for specific traits.
To meet Hardy-Weinberg criteria, a population must be very large (preferably infinite) and exhibit no mutation, no net migration, no natural selection, and no non-random mating. Of the choices, all break one of these criteria except the large population of wildcats.
Example Question #2 : Population Genetics And Hardy Weinberg
A species of birds off the coast of Africa follows Hardy-Weinberg population principles in determining beak color. The dominant phenotype is represented by a black beak, while the recessive phenotype is represented by a grey beak.
If half of the population carries the recessive allele, what percentage of the birds have black beaks? (Assume complete dominance)
65%
75%
25%
50%
75%
If 50% of the population carries the recessive allele, then 50% carry the dominant allele. To determine the genotype breakdown we use the equation p2 + 2pq + q2, where p2 represents homozygous dominant genotype, 2pq represents heterozygous genotype, and q2 represents homozygous recessive genotype. The question tells us the value of allele frequency for the recessive allele, giving us the value of q in this equation. Since p + q = 1, and q is 0.50, p must also be 0.50.
p2 = 0.25
2pq = 0.50
q2 = 0.25
Setting p and q both to 0.50 gives us 25% homozygous dominant, 50% heterozygous, and 25% homozygous recessive; therefore, 75% of the population will display the dominant phenotype (black beak), while 25% will display the recessive phenotype (grey beak). Remember that both homozygous dominant and heterozygous genotypes will display the dominant phenotype.
Example Question #1 : Population Genetics And Hardy Weinberg
Which of the following populations cannot be in Hardy-Weinberg equilibrium?
A small population
A population with no mutation
A randomly mating population
A population with no gene flow
A population with no selection
A small population
By definition, the Hardy-Weinberg principle states that genotype and allele frequencies will remain constant throughout generations. In order for equilibrium to occur, there must be a large, randomly mating population with no selection, genetic drift, migration, or mutation. A small population cannot be in Hardy-Weinberg equilibrium.
Example Question #4 : Mendelian And Population Genetics
In a population of deer mice, the allele for white hair is recessive and the allele for brown hair is dominant. If the population consists of 500 individuals and the frequency of homozygous brown mice is 49%, what is the frequency of the recessive allele?
Assume the population is in Hardy-Weinberg equilibrium.
In Hardy-Weinberg equilibrium, the sum of the dominant allele frequency (p) and the recessive allele frequency (q) is equal to 1.
The question says that 49% of the population consists of mice with the homozygous dominant gene, therefore, the dominant genotype frequency is equal to 0.49.
The question asks us to find the frequency of the recessive allele (q). In order to find the frequency of the recessive allele, we must first find the frequency of the dominant allele (p). According to the Hardy-Weinberg principle, the square root of the homozygous genotype frequency is equal to the allele frequency.
The dominant allele frequency is 0.7. Using this, we can solve for the recessive allele frequency.
Example Question #91 : Genetics
Which of the following is not a requirement for Hardy-Weinberg equilibrium?
Random mating
Natural selection
Absence of migration
Large population size
Natural selection
The following are requirements for Hardy-Weinberg.
- Organisms are diploid
- Only sexual reproduction occurs
- Generations are non overlapping
- Mating is random
- Population size is infinitely large
- Allele frequencies are equal in the sexes
- There is no migration, mutation, or selection
Natural selection would affect allele frequency in a population, thus disrupting Hardy-Weinberg equilibrium.
Example Question #92 : Cell Biology, Molecular Biology, And Genetics
Cystic fibrosis is an autosomal recessive disease. In a population of one hundred individuals, twenty-five are found to have the disease. Assuming Hardy-Weinberg equilibrium, what is the percent of the population that are carriers for cystic fibrosis?
More information is needed
The Hardy-Weinberg formulas tell us that 
In the question, we are told that 25 people out of 100 are homozygous recessive, meaning that 
Using this, we can find that 
If 
We are looking for the frequency of heterozygous individuals (
50% of the population will be heterozygous (carriers) for the trait.
Example Question #93 : Cell Biology, Molecular Biology, And Genetics
In a population that is in Hardy-Weinberg equilibrium there is a gene that has only two alleles. If the dominant gene accounts for 70% of the gene pool, what percentage of the population is heterozygous for the trait?
49%
21%
58%
42%
42%
When a population is in Hardy-Weinberg equilibrium, we can predict the genotypic frequencies found in the population using the equation 
Example Question #92 : Genetics
In a population that is in Hardy-Weinberg equilibrium, there is a gene that has only two alleles that codes for the color of the organism. Which of the following scenarios would not disrupt the Hardy-Weinberg equilibrium of the population?
All color variations in the population have separate niches which allow them to thrive equally
One specific color is able to survive better in the population's present environment
A massive plague destroys 80% of the population
Organisms begin to mate with partners that are the same color as themselves
All color variations in the population have separate niches which allow them to thrive equally
Hardy-Weinberg equilibrium is dependent on five key conditions:
1. The population is very large.
2. Mutations are in equilibrium (no net mutation rate).
3. There is no immigration/emigration that alters the gene pool ratios.
4. There is random mating.
5. There is no selection for the fittest organism taking place in the population.
If any of these conditions are violated in a population, Hardy-Weinberg equilibrium will be disrupted.
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