Mendelian and Population Genetics - Genetics
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A color-blinded man is married to a female carrier.
What percentage of female children born to this couple with be colorblind?
A color-blinded man is married to a female carrier.
What percentage of female children born to this couple with be colorblind?
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Since colorblindness is a sex-linked gene, female children need to have the sex-linked gene from both their mother and father in order to be colorblind. In this case, the mother will donate a colorblinded gene to half of all offspring, while the dad will give his colorblind gene to all his female children. This means that one out of every two female children will have this trait.
Since colorblindness is a sex-linked gene, female children need to have the sex-linked gene from both their mother and father in order to be colorblind. In this case, the mother will donate a colorblinded gene to half of all offspring, while the dad will give his colorblind gene to all his female children. This means that one out of every two female children will have this trait.
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Which of the following is not a condition of Hardy-Weinberg population?
Which of the following is not a condition of Hardy-Weinberg population?
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Hardy-Weinberg is the set of populations that maintain a certain distribution of alleles in a population. In order to maintain this, mating can't choose traits, as that would cause the allele frequency to change over time.
Hardy-Weinberg is the set of populations that maintain a certain distribution of alleles in a population. In order to maintain this, mating can't choose traits, as that would cause the allele frequency to change over time.
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Human birth size is an example of .
Human birth size is an example of .
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Human birth weight is an example of stabilizing selection, because babies that are too heavy or too light are selected against babies that are typically close to the average weight.
Human birth weight is an example of stabilizing selection, because babies that are too heavy or too light are selected against babies that are typically close to the average weight.
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Which of the following is an example of directional selection?
Which of the following is an example of directional selection?
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Directional selection is a process of natural selection when a single phenotype is chosen over another, and thus, many of the organisms in the population are phenotype instead of another extreme.
Directional selection is a process of natural selection when a single phenotype is chosen over another, and thus, many of the organisms in the population are phenotype instead of another extreme.
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What is the probability of a red flower (RR) and a white flower (rr) having offspring with pink flowers (Rr)?
What is the probability of a red flower (RR) and a white flower (rr) having offspring with pink flowers (Rr)?
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Each parent only carries one type of the allele, so when they give the alleles to their children they would have one allele from each parent. This gives them an genotype of Rr for all of their children. The Rr phenotype is pink.
Each parent only carries one type of the allele, so when they give the alleles to their children they would have one allele from each parent. This gives them an genotype of Rr for all of their children. The Rr phenotype is pink.
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There are two very different reproductive strategies in nature: r-selection and k-selection. These strategies are so extreme, we typically observe organisms somewhere in between these two strategies.
Which of the following characteristics is not indicative of r-selection?
There are two very different reproductive strategies in nature: r-selection and k-selection. These strategies are so extreme, we typically observe organisms somewhere in between these two strategies.
Which of the following characteristics is not indicative of r-selection?
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The r-selection strategy for reproduction is typically seen in environments that are very volatile and unpredicatable. It has a variety of characteristics including high brood sizes with a high mortality rate, and fast maturation with very little parental assistance. Low brood sizes are typically seen in the k-selection strategy for reproduction.
The r-selection strategy for reproduction is typically seen in environments that are very volatile and unpredicatable. It has a variety of characteristics including high brood sizes with a high mortality rate, and fast maturation with very little parental assistance. Low brood sizes are typically seen in the k-selection strategy for reproduction.
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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.
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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.
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A rare recessive mutation causes rabbits that are normally white to be pink. If one out of every 625 rabbits is pink, what percentage of the population is heterozygous?
A rare recessive mutation causes rabbits that are normally white to be pink. If one out of every 625 rabbits is pink, what percentage of the population is heterozygous?
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We can use the Hardy-Weinberg equilibrium formulas to calculate the allele frequencies.
We know that the frequency of homozygous recessive (pink) rabbits is 
. This is equal to 
in the Hardy-Weinberg calculation. We can use this information to solve for 
, the recessive allele frequency.
Now that we know the value of 
, we can solve for the value of 
.
The frequency of heterozygotes is equal to 
in the Hardy-Weinberg calculation. Now that we know the frequency of each allele, we can complete this calculation.
We can use the Hardy-Weinberg equilibrium formulas to calculate the allele frequencies.
We know that the frequency of homozygous recessive (pink) rabbits is
Now that we know the value of
The frequency of heterozygotes is equal to
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Eye color in a certain species is decided by a single gene locus. Only two alleles influence eye color in a population of this species that exists in Hardy-Weinberg equilibrium. The dominant allele codes for brown eyes, while the recessive allele codes for blue eyes.
If the frequency of the brown allele is 
, what percent of the population is heterozygous at this locus?
Eye color in a certain species is decided by a single gene locus. Only two alleles influence eye color in a population of this species that exists in Hardy-Weinberg equilibrium. The dominant allele codes for brown eyes, while the recessive allele codes for blue eyes.
If the frequency of the brown allele is
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For problems of this type, we need to understand the Hardy-Weinberg equations:
Here, 
represents the frequency of the dominant allele, while c refers to the frequency of the recessive allele. 
and 
denote the proportion of homozygous dominant and recessive phenotypes, respectively. Finally, the proportion of heterozygotes is denoted by 
.
We already know that 
, and if only two alleles are present in the population, 
must be equal to 
.
Using the values for 
and 
, we can solve for the proportion of heterozygotes using the 
term of the Hardy-Weinberg equation.
For problems of this type, we need to understand the Hardy-Weinberg equations:
Here,
We already know that
Using the values for
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In a certain species of bird, yellow beaks are dominant to orange beaks, and blue feathers are dominant to black feathers.
Two heterozygous birds are crossed. What fraction of the offspring would be expected to have yellow beaks and blue feathers?
In a certain species of bird, yellow beaks are dominant to orange beaks, and blue feathers are dominant to black feathers.
Two heterozygous birds are crossed. What fraction of the offspring would be expected to have yellow beaks and blue feathers?
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This question requires us to do a dihybrid cross. We can represent the gene for beak color with the symbol "A" for dominant yellow and "a" for the recessive orange. Likewise, for feather color, we can use "B" for blue feathers and "b" for black.
The problem states that both birds are heterozygous for each trait, implying that our cross is between two birds with the genotype AaBb.
Now we look at the gametes that can be produced by these parents: AB, Ab, aB, and ab. These gametes can then be used to make a punnet square.
Offspring: 1 AABB, 3 Aabb, 8 AaBa, 3 aaBb, 1 aabb
There are 16 total offspring. 12 of them carry the dominant A allele, giving them the yellow beak phenotype.
Yellow beaks: 1 AABB, 3Aabb, 8 AaBb
Finally, of these 12, 9 carry the dominant B allele for blue feathers.
Yellow beaks and blue feathers: 1 AABB, 8 AaBb
This gives a total of 9 out of the 16 offspring that will express both the yellow beak and blue feather phenotypes.
You should be familiar with the 9:3:3:1 phenotypic ratio resulting from dihybrid crosses.
This question requires us to do a dihybrid cross. We can represent the gene for beak color with the symbol "A" for dominant yellow and "a" for the recessive orange. Likewise, for feather color, we can use "B" for blue feathers and "b" for black.
The problem states that both birds are heterozygous for each trait, implying that our cross is between two birds with the genotype AaBb.
Now we look at the gametes that can be produced by these parents: AB, Ab, aB, and ab. These gametes can then be used to make a punnet square.
Offspring: 1 AABB, 3 Aabb, 8 AaBa, 3 aaBb, 1 aabb
There are 16 total offspring. 12 of them carry the dominant A allele, giving them the yellow beak phenotype.
Yellow beaks: 1 AABB, 3Aabb, 8 AaBb
Finally, of these 12, 9 carry the dominant B allele for blue feathers.
Yellow beaks and blue feathers: 1 AABB, 8 AaBb
This gives a total of 9 out of the 16 offspring that will express both the yellow beak and blue feather phenotypes.
You should be familiar with the 9:3:3:1 phenotypic ratio resulting from dihybrid crosses.
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Consider two traits in pea plants that exhibit complete dominance. Smooth peas are dominant to wrinkled peas, and purple flowers are dominant to white flowers.
A pure breeding plant with purple flowers and wrinkled peas is crossed with a pure breeding plant with white flowers and smooth peas. The first generation is self-pollinated to produce the second generation.
What fraction of the second generation will be heterozygous for both traits?
Consider two traits in pea plants that exhibit complete dominance. Smooth peas are dominant to wrinkled peas, and purple flowers are dominant to white flowers.
A pure breeding plant with purple flowers and wrinkled peas is crossed with a pure breeding plant with white flowers and smooth peas. The first generation is self-pollinated to produce the second generation.
What fraction of the second generation will be heterozygous for both traits?
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When dealing with two traits, it helps to approach each trait separately. The question asks for the fraction of plants in the second generation that are heterozygous for both traits.
First, we will look at the first generation. The parents are both pure breeding, meaning they are homozygous for each trait. One is purple (dominant) and wrinkled (recessive), while the other is white (recessive) and round (dominant). The result will be dihybrid offspring.
Parent cross: PPrr x ppRR
Offspring: All offspring will be PpRr and exhibit both dominant phenotypes (purple and round).
Now we will look at the first generation self-cross for each trait.
First generation: PpRr x PpRr
Offspring for color: 1 PP, 2 Pp, 1 pp; 3 purple and 1 white.
Offspring for seeds: 1 RR, 2 Rr, 1 rr; 3 round and 1 wrinkled.
We can see that half of the offspring will be heterozygous for color, and half of the offspring will be heterozygous for seed shape.
Since we are looking for plants that have both of these traits, we multiply these two probabilities together.
When dealing with two traits, it helps to approach each trait separately. The question asks for the fraction of plants in the second generation that are heterozygous for both traits.
First, we will look at the first generation. The parents are both pure breeding, meaning they are homozygous for each trait. One is purple (dominant) and wrinkled (recessive), while the other is white (recessive) and round (dominant). The result will be dihybrid offspring.
Parent cross: PPrr x ppRR
Offspring: All offspring will be PpRr and exhibit both dominant phenotypes (purple and round).
Now we will look at the first generation self-cross for each trait.
First generation: PpRr x PpRr
Offspring for color: 1 PP, 2 Pp, 1 pp; 3 purple and 1 white.
Offspring for seeds: 1 RR, 2 Rr, 1 rr; 3 round and 1 wrinkled.
We can see that half of the offspring will be heterozygous for color, and half of the offspring will be heterozygous for seed shape.
Since we are looking for plants that have both of these traits, we multiply these two probabilities together.
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Consider a plant with the following characteristics.
Round leaves (R) are dominant to pointed leaves (r).
White flowers (W) are dominant to pink flowers (w).
Plants heterozygous for both traits are crossed.
What is the probability of obtaining a plant with pointed leaves and white flowers?
Consider a plant with the following characteristics.
Round leaves (R) are dominant to pointed leaves (r).
White flowers (W) are dominant to pink flowers (w).
Plants heterozygous for both traits are crossed.
What is the probability of obtaining a plant with pointed leaves and white flowers?
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The genotype to obtain pointed leaves is rr, while the genotypes to obtain white flowers are WW or Ww. Determine the frequence of obtaining WWrr or Wwrr using a Punnett Square.
You should be familiar with the ratios represented in a dihybrid cross: 9:3:3:1. There will be nine inidividuals with both dominant traits (pointed leaves and white flowers), three individuals dominant for one trait (round leaves and pink flowers), three individuals dominant for the other trait (pointed leaves and white flowers), and only one individual recessive for both traits (pointed leaves and pink flowers).
The genotype to obtain pointed leaves is rr, while the genotypes to obtain white flowers are WW or Ww. Determine the frequence of obtaining WWrr or Wwrr using a Punnett Square.
You should be familiar with the ratios represented in a dihybrid cross: 9:3:3:1. There will be nine inidividuals with both dominant traits (pointed leaves and white flowers), three individuals dominant for one trait (round leaves and pink flowers), three individuals dominant for the other trait (pointed leaves and white flowers), and only one individual recessive for both traits (pointed leaves and pink flowers).
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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.
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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.
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Which definition below defines allelic variation?
Which definition below defines allelic variation?
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Allelic variation is a mutation in the SAME gene causing different diseases. Genetic heterogeneity is when different mutations can lead to the same disease. Variable expressivity is the varying degrees of disease with the same gene mutated. Penetrance refers to the percentage of people with a mutation that develop a disorder.
Allelic variation is a mutation in the SAME gene causing different diseases. Genetic heterogeneity is when different mutations can lead to the same disease. Variable expressivity is the varying degrees of disease with the same gene mutated. Penetrance refers to the percentage of people with a mutation that develop a disorder.
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Black fur (A) is dominant to brown fur (a) and brown eyes (B) are dominant to blue eyes (b) in mice. Two mice are heterozygous for both traits. If one of the offspring shows a phenotype for green eyes, what is most likely the best explanation?
Black fur (A) is dominant to brown fur (a) and brown eyes (B) are dominant to blue eyes (b) in mice. Two mice are heterozygous for both traits. If one of the offspring shows a phenotype for green eyes, what is most likely the best explanation?
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The best choice is that the individual has a mutation that accounts for his/her green eyes. This mutation would yield a new phenotype that was not a result of direct inheritance from the parent generation.
Codominance cannot only occur in one individual offspring; rather it would occur in some form in all offspring with respect to the given trait. Independent assortment always occurs in cases of typical Mendelian genetics.
The best choice is that the individual has a mutation that accounts for his/her green eyes. This mutation would yield a new phenotype that was not a result of direct inheritance from the parent generation.
Codominance cannot only occur in one individual offspring; rather it would occur in some form in all offspring with respect to the given trait. Independent assortment always occurs in cases of typical Mendelian genetics.
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In a dihybrid cross (AaBb x AaBb), how many total genotypes are possible in the offspring?
In a dihybrid cross (AaBb x AaBb), how many total genotypes are possible in the offspring?
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The alleles for gene A assort independently from the alleles of gene B, meaning that the genotype for one does not affect the genotype of the other. Even though there are two genes, we can solve this problem by answering the question separately for the two genes.
There are three possible genotypes with respect to the A gene (AA, Aa, aa) and three possible genotypes with respect to the B gene (BB, Bb, bb). Since genes A and B assort independently, the possible offspring will be the product of the possibilities for each separate gene.
Listed out, these genotypes are: AABB, AABb, AaBB, AAbb, AaBb, aaBB, Aabb, aaBb, aabb.
The alleles for gene A assort independently from the alleles of gene B, meaning that the genotype for one does not affect the genotype of the other. Even though there are two genes, we can solve this problem by answering the question separately for the two genes.
There are three possible genotypes with respect to the A gene (AA, Aa, aa) and three possible genotypes with respect to the B gene (BB, Bb, bb). Since genes A and B assort independently, the possible offspring will be the product of the possibilities for each separate gene.
Listed out, these genotypes are: AABB, AABb, AaBB, AAbb, AaBb, aaBB, Aabb, aaBb, aabb.
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How is an allele different from a genotype?
How is an allele different from a genotype?
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An allele is the specific gene out of many for a given trait. The genotype is the combination of alleles that are present in the individual.
An allele is the specific gene out of many for a given trait. The genotype is the combination of alleles that are present in the individual.
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What is a homozygous individual?
What is a homozygous individual?
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A homozygous individual expresses the same two alleles for a given trait. An example would be a person with blue eyes would have two recessive alleles for that eye color, bb.
A homozygous individual expresses the same two alleles for a given trait. An example would be a person with blue eyes would have two recessive alleles for that eye color, bb.
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If a tall pea plant with the genotype Tt is crossed with a short pea plant with the genotype tt (homozygous recessive), what should the F1 progeny consist of?
If a tall pea plant with the genotype Tt is crossed with a short pea plant with the genotype tt (homozygous recessive), what should the F1 progeny consist of?
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Using a punnett square one can see we get 1/2 with genotype Tt and half with genotype tt.
T t
t Tt tt
t Tt tt
Using a punnett square one can see we get 1/2 with genotype Tt and half with genotype tt.
T t
t Tt tt
t Tt tt
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If you cross a pea plant that is tall and has genotype Tt with another pea plant that is tall and has genotype Tt, what should their F1 progeny look like?
If you cross a pea plant that is tall and has genotype Tt with another pea plant that is tall and has genotype Tt, what should their F1 progeny look like?
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Using a pungent square, one can determine that 1/2 will have genotype Tt and will be tall, 1/4 will have genotype TT and will also be tall, 1/4 will have genotype tt and will be short.
T t
T TT Tt
t Tt tt
Using a pungent square, one can determine that 1/2 will have genotype Tt and will be tall, 1/4 will have genotype TT and will also be tall, 1/4 will have genotype tt and will be short.
T t
T TT Tt
t Tt tt
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