Population Genetics and Hardy-Weinberg - MCAT Biological and Biochemical Foundations of Living Systems
Card 1 of 248
Which statement best describes the Hardy-Weinberg principle?
Which statement best describes the Hardy-Weinberg principle?
Tap to reveal answer
Hardy-Weinberg principle mathematically describes how inheritance does not change allele frequency in large populations. This helps explain why dominant and recessive alleles are both found in populations. A change in the predicted genotypes of a population may indicate evolotuion at work.
Hardy-Weinberg principle mathematically describes how inheritance does not change allele frequency in large populations. This helps explain why dominant and recessive alleles are both found in populations. A change in the predicted genotypes of a population may indicate evolotuion at work.
← Didn't Know|Knew It →
In a population of a particular island, 64% of individuals have a homozygous recessive genotype. Assuming the population correlates with Hardy-Weinberg principles, what percentage of individuals in the next generation will be heterozygous?
In a population of a particular island, 64% of individuals have a homozygous recessive genotype. Assuming the population correlates with Hardy-Weinberg principles, what percentage of individuals in the next generation will be heterozygous?
Tap to reveal answer
Use equations p + q = 1 and p2 + 2pq + q2 = 1.
If 64% is homozygous recessive genotype, then q2 = 0.64.
Then solve for p and q.
q = 0.8 and p = 0.2. The frequency of heterozygous individuals is 2pq or 2(0.2)(0.8) = 0.32
Use equations p + q = 1 and p2 + 2pq + q2 = 1.
If 64% is homozygous recessive genotype, then q2 = 0.64.
Then solve for p and q.
q = 0.8 and p = 0.2. The frequency of heterozygous individuals is 2pq or 2(0.2)(0.8) = 0.32
← Didn't Know|Knew It →
A certain island-nation with a population of 200,000 has laws which severely restrict travel onto or off the island. There is an absolute prohibition against marrying foreigners, but island natives may marry as they wish. A non-lethal recessive genetic condition affects 2,000 of the people. How many carriers of this condition live on the island?
I. 198,000
II. 96,000
III. 36,000
IV. 12,400
V. 9,600
A certain island-nation with a population of 200,000 has laws which severely restrict travel onto or off the island. There is an absolute prohibition against marrying foreigners, but island natives may marry as they wish. A non-lethal recessive genetic condition affects 2,000 of the people. How many carriers of this condition live on the island?
I. 198,000
II. 96,000
III. 36,000
IV. 12,400
V. 9,600
Tap to reveal answer
The question assumes unusual conditions that must be met for a Hardy-Weinberg genetic equilibrium to exist. The population is large and isolated. The gene is assumed to be stable. Mating is "random," but only within the population. Here, the affected homozygous recessive people number 2,000—one one hundredth of the population.
In Hardy-Weinberg terms, this means q squared is 0.01 and q (the frequency of the recessive allele) is 0.1. Since p + q = 1, then p, the frequency of the dominant allele, must be 0.9. The carriers are denoted by 2pq because p + q = 1, and therefore p2 + 2pq + q2 is also equal to one. Here, 2 (0.9)(0.1) = 0.18, meaning that 18% of the 200,000 population, or 36,000 persons, are heterozygous carriers. The strict conditions for Hardy-Weinberg equilibrium are almost never satisfied in human populations.
The question assumes unusual conditions that must be met for a Hardy-Weinberg genetic equilibrium to exist. The population is large and isolated. The gene is assumed to be stable. Mating is "random," but only within the population. Here, the affected homozygous recessive people number 2,000—one one hundredth of the population.
In Hardy-Weinberg terms, this means q squared is 0.01 and q (the frequency of the recessive allele) is 0.1. Since p + q = 1, then p, the frequency of the dominant allele, must be 0.9. The carriers are denoted by 2pq because p + q = 1, and therefore p2 + 2pq + q2 is also equal to one. Here, 2 (0.9)(0.1) = 0.18, meaning that 18% of the 200,000 population, or 36,000 persons, are heterozygous carriers. The strict conditions for Hardy-Weinberg equilibrium are almost never satisfied in human populations.
← Didn't Know|Knew It →
All of the following are important aspects of Hardy-Weinberg equilibrium EXCEPT .
All of the following are important aspects of Hardy-Weinberg equilibrium EXCEPT .
Tap to reveal answer
Hardy-Weinberg equilibrium is acheived when the gene frequencies in a population do not change over time. This means the population is not evolving. The five conditions for this are large population size, no mutations, random mating, no net migration, and equally successful reproduction potential for all genes in the population. Temperature is a directly important aspect of this.
Hardy-Weinberg equilibrium is acheived when the gene frequencies in a population do not change over time. This means the population is not evolving. The five conditions for this are large population size, no mutations, random mating, no net migration, and equally successful reproduction potential for all genes in the population. Temperature is a directly important aspect of this.
← Didn't Know|Knew It →
A botanist is reviewing a set of sequenced genomes from the tobacco plants he uses in his lab. He notices frequency of plants that are phenotypically recessive is 0.16. What are the frequencies of heterozygotes and homozygous dominant plants?
A botanist is reviewing a set of sequenced genomes from the tobacco plants he uses in his lab. He notices frequency of plants that are phenotypically recessive is 0.16. What are the frequencies of heterozygotes and homozygous dominant plants?
Tap to reveal answer
We use the formula: 
where p and q are the allelic frequencies. We know that 
is the frequency of homozygous recessive individuals, so q must be 0.4 That means that p must be 0.6, because p and q must add up to 1. From there, we can just plug in 0.4 a 0.6 to get our answer.
We use the formula:
where p and q are the allelic frequencies. We know that
← Didn't Know|Knew It →
Which of the following conditions are required for a population to be in Hardy-Weinberg equilibrium?
Which of the following conditions are required for a population to be in Hardy-Weinberg equilibrium?
Tap to reveal answer
The correct answer is "all of these." The choices listed are all required assumptions for a population to achieve Hardy-Weinberg equilibrium. "No natural selection" is another condition that is not listed here, bringing the total to 5 conditions.
The correct answer is "all of these." The choices listed are all required assumptions for a population to achieve Hardy-Weinberg equilibrium. "No natural selection" is another condition that is not listed here, bringing the total to 5 conditions.
← Didn't Know|Knew It →
If forty percent of a Hardy-Weinberg population is phenotypic for an autosomal recessive trait, approximately what percent of the population will be heterozygous?
If forty percent of a Hardy-Weinberg population is phenotypic for an autosomal recessive trait, approximately what percent of the population will be heterozygous?
Tap to reveal answer
The phenotype for a Hardy-Weinberg population can be defined as p + q =1, where p and q represent dominant and recessive frequencies. The genotypes for the population can be defined as p2+2pq+q2=1.
In this formula, p2 and q2 represent the homozygous dominant and homozygous recessive genotype frequencies respectively, and 2pq represents the heterozygous genotype frequency in the population.
Since 40% of the population is phenotypic recessive, we know that 60% of the population is phenotypic dominant.
q = 0.4
p + q =1; p = 0.6
p2 and q2 are equal to 0.16 and 0.36 respectively. Solving for 2pq gives us 0.48, so approximately 48% of the population will be heterozygous.
The phenotype for a Hardy-Weinberg population can be defined as p + q =1, where p and q represent dominant and recessive frequencies. The genotypes for the population can be defined as p2+2pq+q2=1.
In this formula, p2 and q2 represent the homozygous dominant and homozygous recessive genotype frequencies respectively, and 2pq represents the heterozygous genotype frequency in the population.
Since 40% of the population is phenotypic recessive, we know that 60% of the population is phenotypic dominant.
q = 0.4
p + q =1; p = 0.6
p2 and q2 are equal to 0.16 and 0.36 respectively. Solving for 2pq gives us 0.48, so approximately 48% of the population will be heterozygous.
← Didn't Know|Knew It →
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?
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?
Tap to reveal answer
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.
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.
← Didn't Know|Knew It →
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
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
Tap to reveal answer
Hardy-Weinberg equilibrium states that there is random mating, no immigration/emigration, and that there are no mutations.
Hardy-Weinberg equilibrium states that there is random mating, no immigration/emigration, and that there are no mutations.
← Didn't Know|Knew It →
Which of these populations could meet the criteria required for Hardy-Weinberg equilibrium?
Which of these populations could meet the criteria required for Hardy-Weinberg equilibrium?
Tap to reveal answer
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.
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.
← Didn't Know|Knew It →
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)
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)
Tap to reveal answer
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.
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.
← Didn't Know|Knew It →
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 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.
Tap to reveal answer
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.
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.
← Didn't Know|Knew It →
Which of the following populations cannot be in Hardy-Weinberg equilibrium?
Which of the following populations cannot be in Hardy-Weinberg equilibrium?
Tap to reveal answer
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.
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.
← Didn't Know|Knew It →
Researchers are studying a disease that causes neurological deficits in humans. They have identified the disorder as autosomal dominant, but notice that about 20% of people with the dominant disease allele do not express any of the associated neurological impairment. What genetics term explains this phenomenon?
Researchers are studying a disease that causes neurological deficits in humans. They have identified the disorder as autosomal dominant, but notice that about 20% of people with the dominant disease allele do not express any of the associated neurological impairment. What genetics term explains this phenomenon?
Tap to reveal answer
In this example, some individuals with a certain genotype do not express the expected phenotype (symptoms of the disease) at all. The only term that properly describes this effect is reduced penetrance. Penetrance refers to the percent of individuals with a specific genotype who express the associated phenotype. In most common examples given in genetics courses, autosomal dominant diseases are 100% penetrant, meaning that all individuals with one disease allele will show symptoms to some extent. Here, however, the disease appears to show 80% penetrance.
One term often confused with penetrance is expressivity. This refers to the extent that the phenotype is expressed, and is only applicable when penetrance is 100%. If all of the individuals showed symptoms of the disease, but some showed slightly different defects than others, the disease would have variable expressivity. The other answer choices refer to unrelated genetics concepts.
In this example, some individuals with a certain genotype do not express the expected phenotype (symptoms of the disease) at all. The only term that properly describes this effect is reduced penetrance. Penetrance refers to the percent of individuals with a specific genotype who express the associated phenotype. In most common examples given in genetics courses, autosomal dominant diseases are 100% penetrant, meaning that all individuals with one disease allele will show symptoms to some extent. Here, however, the disease appears to show 80% penetrance.
One term often confused with penetrance is expressivity. This refers to the extent that the phenotype is expressed, and is only applicable when penetrance is 100%. If all of the individuals showed symptoms of the disease, but some showed slightly different defects than others, the disease would have variable expressivity. The other answer choices refer to unrelated genetics concepts.
← Didn't Know|Knew It →
Which of the following is not a requirement for Hardy-Weinberg equilibrium?
Which of the following is not a requirement for Hardy-Weinberg equilibrium?
Tap to reveal answer
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.
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.
← Didn't Know|Knew It →
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?
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?
Tap to reveal answer
The Hardy-Weinberg formulas tell us that 
and 
, where 
is the dominant allele frequency and 
is the recessive allele frequency. 
is the frequency of homozygous dominant individuals in a population, 
is the frequency of heterozygous individuals, and 
is the frequency of homozygous recessive individuals.
In the question, we are told that 25 people out of 100 are homozygous recessive, meaning that 
.
Using this, we can find that 
.
If 
, and 
, then 
.
We are looking for the frequency of heterozygous individuals (
).
50% of the population will be heterozygous (carriers) for the trait.
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.
← Didn't Know|Knew It →
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?
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?
Tap to reveal answer
When a population is in Hardy-Weinberg equilibrium, we can predict the genotypic frequencies found in the population using the equation 
, where 
is the frequency of the dominant allele, and 
is the frequency of the recessive allele. Since 
and 
account for the homozygotes in the population, we can find the frequency of the heterozygotes using the 
portion of the equation. We can first solve for 
using the relationship 
.
When a population is in Hardy-Weinberg equilibrium, we can predict the genotypic frequencies found in the population using the equation
← Didn't Know|Knew It →
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?
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?
Tap to reveal answer
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.
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.
← Didn't Know|Knew It →
Which of the following is not a necessary condition of Hardy-Weinberg equilibrium?
Which of the following is not a necessary condition of Hardy-Weinberg equilibrium?
Tap to reveal answer
There are five conditions for Hardy-Weinberg equilibrium.
- No natural selection
- Large population
- Random mating
- No mutations
- No migration
There are five conditions for Hardy-Weinberg equilibrium.
- No natural selection
- Large population
- Random mating
- No mutations
- No migration
← Didn't Know|Knew It →
The concept of genomic imprinting is important in human genetics. In genomic imprinting, a certain region of DNA is only expressed by one of the two chromosomes that make up a typical homologous pair. In healthy individuals, genomic imprinting results in the silencing of genes in a certain section of the maternal chromosome 15. The DNA in this part of the chromosome is "turned off" by the addition of methyl groups to the DNA molecule. Healthy people will thus only have expression of this section of chromosome 15 from paternally-derived DNA.
The two classic human diseases that illustrate defects in genomic imprinting are Prader-Willi and Angelman Syndromes. In Prader-Willi Syndrome, the section of paternal chromosome 15 that is usually expressed is disrupted, such as by a chromosomal deletion. In Angelman Syndrome, maternal genes in this section are deleted, while paternal genes are silenced. Prader-Willi Syndrome is thus closely linked to paternal inheritance, while Angelman Syndrome is linked to maternal inheritance.
Figure 1 shows the chromosome 15 homologous pair for a child with Prader-Willi Syndrome. The parental chromosomes are also shown. The genes on the mother’s chromosomes are silenced normally, as represented by the black boxes. At once, there is also a chromosomal deletion on one of the paternal chromosomes. The result is that the child does not have any genes expressed that are normally found on that region of this chromosome.
A child is diagnosed with a genetic disease, and two years later his parents have another child. The second child also inherited the gene mutation, but does not express the disease. Which of the following is reduced in the second child?
The concept of genomic imprinting is important in human genetics. In genomic imprinting, a certain region of DNA is only expressed by one of the two chromosomes that make up a typical homologous pair. In healthy individuals, genomic imprinting results in the silencing of genes in a certain section of the maternal chromosome 15. The DNA in this part of the chromosome is "turned off" by the addition of methyl groups to the DNA molecule. Healthy people will thus only have expression of this section of chromosome 15 from paternally-derived DNA.
The two classic human diseases that illustrate defects in genomic imprinting are Prader-Willi and Angelman Syndromes. In Prader-Willi Syndrome, the section of paternal chromosome 15 that is usually expressed is disrupted, such as by a chromosomal deletion. In Angelman Syndrome, maternal genes in this section are deleted, while paternal genes are silenced. Prader-Willi Syndrome is thus closely linked to paternal inheritance, while Angelman Syndrome is linked to maternal inheritance.
Figure 1 shows the chromosome 15 homologous pair for a child with Prader-Willi Syndrome. The parental chromosomes are also shown. The genes on the mother’s chromosomes are silenced normally, as represented by the black boxes. At once, there is also a chromosomal deletion on one of the paternal chromosomes. The result is that the child does not have any genes expressed that are normally found on that region of this chromosome.
A child is diagnosed with a genetic disease, and two years later his parents have another child. The second child also inherited the gene mutation, but does not express the disease. Which of the following is reduced in the second child?
Tap to reveal answer
The second child has reduced penetrance. Reduced penetrance is found when a given genotype (the presence of the mutation) fails to "penetrate" the phenotype. In other words, even though the second child has the dysfunctional allele, he does not have a clinical disease.
Penetrance refers to the level of dominance. These alleles can still be described as dominant or recessive, but penetrance describes the degree of dominance along a spectrum.
The second child has reduced penetrance. Reduced penetrance is found when a given genotype (the presence of the mutation) fails to "penetrate" the phenotype. In other words, even though the second child has the dysfunctional allele, he does not have a clinical disease.
Penetrance refers to the level of dominance. These alleles can still be described as dominant or recessive, but penetrance describes the degree of dominance along a spectrum.
← Didn't Know|Knew It →