Help with Mendelian Inheritance - GRE
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A scientist has been working with a new species of plant. He has found that there are two separate genes, which segregate according to standard Mendelian genetics, that are capable of producing the same phenotype. A single dominant allele from either gene confers red coloration of the plant's flowers. Without any dominant alleles the flowers are white. If he crosses two plants heterozygous for both traits, what will be the resulting phenotypic ratios of the offspring?
A scientist has been working with a new species of plant. He has found that there are two separate genes, which segregate according to standard Mendelian genetics, that are capable of producing the same phenotype. A single dominant allele from either gene confers red coloration of the plant's flowers. Without any dominant alleles the flowers are white. If he crosses two plants heterozygous for both traits, what will be the resulting phenotypic ratios of the offspring?
This problem requires a standard dihybrid cross. The crossed genotypes are AaBb x AaBb. This results in a phenotypic ratio of 9 dominant for both traits, 3 dominant for a single trait, 3 dominant for the other trait, and 1 recessive for both traits. In this cross, it will result in: 9 AxBx, 3 Axbb, 3 aaBx, and 1 aabb.
Since we know that the genes are both capable of making the red coloration we actually need to add together all of the choices that contain at least a single dominant allele. Essentially, AxBx, Axbb, and aaBx all show the exact same phenotype. This leaves us with a 15:1 ratio of red to white flowers.
This problem requires a standard dihybrid cross. The crossed genotypes are AaBb x AaBb. This results in a phenotypic ratio of 9 dominant for both traits, 3 dominant for a single trait, 3 dominant for the other trait, and 1 recessive for both traits. In this cross, it will result in: 9 AxBx, 3 Axbb, 3 aaBx, and 1 aabb.
Since we know that the genes are both capable of making the red coloration we actually need to add together all of the choices that contain at least a single dominant allele. Essentially, AxBx, Axbb, and aaBx all show the exact same phenotype. This leaves us with a 15:1 ratio of red to white flowers.
Compare your answer with the correct one above
In a species of ant, black coloration is dominant to white. A scientist is operating under the assumption that this gene follows basic Mendelian principles; however, after crossing two heterozygotes he obtained a ratio of 2:1 of dominant to recessive offspring. Which of the following could explain this result?
In a species of ant, black coloration is dominant to white. A scientist is operating under the assumption that this gene follows basic Mendelian principles; however, after crossing two heterozygotes he obtained a ratio of 2:1 of dominant to recessive offspring. Which of the following could explain this result?
The only answer that properly explains a 2:1 ratio is if the homozygous dominant phenotype is lethal. In our punnett square, this would give a two-thirds chance for a heterozygous offspring and a one-third chance for a recessive offspring. We know the recessive phenotype is not lethal because homozygous recessive offspring were produced.
Parents: Aa x Aa
Offspring genotypes: AA, Aa, Aa, aa
Offspring phenotypes: lethal, dominant, dominant, recessive (only three live offspring produced)
Offspring ratio: 2 dominant to 1 recessive
There is also no evidence that codominance or incomplete dominance is present. If black and white spotted offspring or gray offspring were produced then these theories would have merit.
The only answer that properly explains a 2:1 ratio is if the homozygous dominant phenotype is lethal. In our punnett square, this would give a two-thirds chance for a heterozygous offspring and a one-third chance for a recessive offspring. We know the recessive phenotype is not lethal because homozygous recessive offspring were produced.
Parents: Aa x Aa
Offspring genotypes: AA, Aa, Aa, aa
Offspring phenotypes: lethal, dominant, dominant, recessive (only three live offspring produced)
Offspring ratio: 2 dominant to 1 recessive
There is also no evidence that codominance or incomplete dominance is present. If black and white spotted offspring or gray offspring were produced then these theories would have merit.
Compare your answer with the correct one above
A child is curious to know what his blood type is, but he only knows his parents' blood types. If his mother had blood type A and his father had blood type AB, what are the potential blood types the child might have?
A child is curious to know what his blood type is, but he only knows his parents' blood types. If his mother had blood type A and his father had blood type AB, what are the potential blood types the child might have?
We are not given the mother's full genotype in the question; she could reasonably carry two A alleles, or an A allele and a recessive O allele. We know that the father must carry one copy of the A allele and one copy of the B allele.
Two punnett squares can answer this question, corresponding to the two possible maternal genotypes: one crossing AA x AB and the other crossing AO x AB. From the first cross there is a 50% chance of blood type A versus 50% chance of blood type AB (half AA and half AB). The second cross shows that there is a potential chance of 50% for type A, 25% for type AB, and 25% for type B (one AA, one OA, one AB, and one OB).
Based on these possibilities, the child could have blood type A, B, or AB. The child cannot have blood type O.
We are not given the mother's full genotype in the question; she could reasonably carry two A alleles, or an A allele and a recessive O allele. We know that the father must carry one copy of the A allele and one copy of the B allele.
Two punnett squares can answer this question, corresponding to the two possible maternal genotypes: one crossing AA x AB and the other crossing AO x AB. From the first cross there is a 50% chance of blood type A versus 50% chance of blood type AB (half AA and half AB). The second cross shows that there is a potential chance of 50% for type A, 25% for type AB, and 25% for type B (one AA, one OA, one AB, and one OB).
Based on these possibilities, the child could have blood type A, B, or AB. The child cannot have blood type O.
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A breeder performs a standard dihybrid cross between two plants that are heterozygous for both traits in question. How many unique genotypes could be present in the resulting offspring?
A breeder performs a standard dihybrid cross between two plants that are heterozygous for both traits in question. How many unique genotypes could be present in the resulting offspring?
There are nine distinct genotypes present after a standard dihybrid cross. This question can easily be answered by setting up a Punnett square (AaBb x AaBb) and counting the number of unique genotypes present after doing the cross. The numbers also conveniently work out that however many offspring display the dominant phenotype is equal to the number to of genotypes present (this is true for monohybrid and trihybrid crosses as well).
There are nine distinct genotypes present after a standard dihybrid cross. This question can easily be answered by setting up a Punnett square (AaBb x AaBb) and counting the number of unique genotypes present after doing the cross. The numbers also conveniently work out that however many offspring display the dominant phenotype is equal to the number to of genotypes present (this is true for monohybrid and trihybrid crosses as well).
Compare your answer with the correct one above
A scientist is performing a monohybrid homozygous cross: tall plants crossed with short plants. What fraction of the F2 generation are homozygous tall?
A scientist is performing a monohybrid homozygous cross: tall plants crossed with short plants. What fraction of the F2 generation are homozygous tall?
A monohybrid cross between two homozygous plants would involve a parental generation that looked like this: SS (tall) x ss (short). The F1 generation would produce only heterozygous tall plants (Ss). The F2 generation would produce offspring from the following cross: Ss x Ss. A punnett square would reveal that the F2 generation would have 25% homozygous tall (SS), 50% heterozygous tall (Ss), and 25% homozygous short plants. Note that we do not need information regarding which trait is dominant in this case, and we would still get the correct answer if we took short as the dominant phenotype.
A monohybrid cross between two homozygous plants would involve a parental generation that looked like this: SS (tall) x ss (short). The F1 generation would produce only heterozygous tall plants (Ss). The F2 generation would produce offspring from the following cross: Ss x Ss. A punnett square would reveal that the F2 generation would have 25% homozygous tall (SS), 50% heterozygous tall (Ss), and 25% homozygous short plants. Note that we do not need information regarding which trait is dominant in this case, and we would still get the correct answer if we took short as the dominant phenotype.
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In apple trees, the allele for white blossoms is dominant over the allele for pink blossoms. Two trees heterozygous for this gene are crossed. What is the phenotype ratio of the offspring?
In apple trees, the allele for white blossoms is dominant over the allele for pink blossoms. Two trees heterozygous for this gene are crossed. What is the phenotype ratio of the offspring?
The crossing of two heterozygous parents will yield 1 homozyougs dominant offspring, 1 homozygous recessive offspring and 2 heterozygous offspring. Since white blossoms is the dominant allele, the heterozygous offspring will be white leading to a phenotypic ratio of 3 white : 1 pink blossom.
The crossing of two heterozygous parents will yield 1 homozyougs dominant offspring, 1 homozygous recessive offspring and 2 heterozygous offspring. Since white blossoms is the dominant allele, the heterozygous offspring will be white leading to a phenotypic ratio of 3 white : 1 pink blossom.
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Assume complete dominance inheritance for the following question.
A pure-breeding red flower is mated with a pure-breeding white flower. All offspring are red in color; this is the F1 generation. Two of these offspring flowers are then mated with one another, and have F2 offspring.
Which of the following is true of the F2 offspring?
Assume complete dominance inheritance for the following question.
A pure-breeding red flower is mated with a pure-breeding white flower. All offspring are red in color; this is the F1 generation. Two of these offspring flowers are then mated with one another, and have F2 offspring.
Which of the following is true of the F2 offspring?
Since we had pure-breeding parents (also known as homozygotes for their respective colors), we can safely say the F1 offspring are heterozygotes and have a red allele and a white allele. When crossing these offspring with one another, we will expect to get a 3:1 ratio of red to white flowers. Not all flowers will be red, but 75% of the flowers will be.
Shown below is the punnett square that reflects this conclusion. (Note that "A" represents a red allele and "a" represents a white allele):
A a
A AA (red) Aa (red)
a Aa (red) aa (white)
Since we had pure-breeding parents (also known as homozygotes for their respective colors), we can safely say the F1 offspring are heterozygotes and have a red allele and a white allele. When crossing these offspring with one another, we will expect to get a 3:1 ratio of red to white flowers. Not all flowers will be red, but 75% of the flowers will be.
Shown below is the punnett square that reflects this conclusion. (Note that "A" represents a red allele and "a" represents a white allele):
A a
A AA (red) Aa (red)
a Aa (red) aa (white)
Compare your answer with the correct one above
In a species of ant, black coloration is dominant to white. A scientist is operating under the assumption that this gene follows basic Mendelian principles; however, after crossing two heterozygotes he obtained a ratio of 2:1 of dominant to recessive offspring. Which of the following could explain this result?
In a species of ant, black coloration is dominant to white. A scientist is operating under the assumption that this gene follows basic Mendelian principles; however, after crossing two heterozygotes he obtained a ratio of 2:1 of dominant to recessive offspring. Which of the following could explain this result?
The only answer that properly explains a 2:1 ratio is if the homozygous dominant phenotype is lethal. In our punnett square, this would give a two-thirds chance for a heterozygous offspring and a one-third chance for a recessive offspring. We know the recessive phenotype is not lethal because homozygous recessive offspring were produced.
Parents: Aa x Aa
Offspring genotypes: AA, Aa, Aa, aa
Offspring phenotypes: lethal, dominant, dominant, recessive (only three live offspring produced)
Offspring ratio: 2 dominant to 1 recessive
There is also no evidence that codominance or incomplete dominance is present. If black and white spotted offspring or gray offspring were produced then these theories would have merit.
The only answer that properly explains a 2:1 ratio is if the homozygous dominant phenotype is lethal. In our punnett square, this would give a two-thirds chance for a heterozygous offspring and a one-third chance for a recessive offspring. We know the recessive phenotype is not lethal because homozygous recessive offspring were produced.
Parents: Aa x Aa
Offspring genotypes: AA, Aa, Aa, aa
Offspring phenotypes: lethal, dominant, dominant, recessive (only three live offspring produced)
Offspring ratio: 2 dominant to 1 recessive
There is also no evidence that codominance or incomplete dominance is present. If black and white spotted offspring or gray offspring were produced then these theories would have merit.
Compare your answer with the correct one above
A scientist has been working with a new species of plant. He has found that there are two separate genes, which segregate according to standard Mendelian genetics, that are capable of producing the same phenotype. A single dominant allele from either gene confers red coloration of the plant's flowers. Without any dominant alleles the flowers are white. If he crosses two plants heterozygous for both traits, what will be the resulting phenotypic ratios of the offspring?
A scientist has been working with a new species of plant. He has found that there are two separate genes, which segregate according to standard Mendelian genetics, that are capable of producing the same phenotype. A single dominant allele from either gene confers red coloration of the plant's flowers. Without any dominant alleles the flowers are white. If he crosses two plants heterozygous for both traits, what will be the resulting phenotypic ratios of the offspring?
This problem requires a standard dihybrid cross. The crossed genotypes are AaBb x AaBb. This results in a phenotypic ratio of 9 dominant for both traits, 3 dominant for a single trait, 3 dominant for the other trait, and 1 recessive for both traits. In this cross, it will result in: 9 AxBx, 3 Axbb, 3 aaBx, and 1 aabb.
Since we know that the genes are both capable of making the red coloration we actually need to add together all of the choices that contain at least a single dominant allele. Essentially, AxBx, Axbb, and aaBx all show the exact same phenotype. This leaves us with a 15:1 ratio of red to white flowers.
This problem requires a standard dihybrid cross. The crossed genotypes are AaBb x AaBb. This results in a phenotypic ratio of 9 dominant for both traits, 3 dominant for a single trait, 3 dominant for the other trait, and 1 recessive for both traits. In this cross, it will result in: 9 AxBx, 3 Axbb, 3 aaBx, and 1 aabb.
Since we know that the genes are both capable of making the red coloration we actually need to add together all of the choices that contain at least a single dominant allele. Essentially, AxBx, Axbb, and aaBx all show the exact same phenotype. This leaves us with a 15:1 ratio of red to white flowers.
Compare your answer with the correct one above
A child is curious to know what his blood type is, but he only knows his parents' blood types. If his mother had blood type A and his father had blood type AB, what are the potential blood types the child might have?
A child is curious to know what his blood type is, but he only knows his parents' blood types. If his mother had blood type A and his father had blood type AB, what are the potential blood types the child might have?
We are not given the mother's full genotype in the question; she could reasonably carry two A alleles, or an A allele and a recessive O allele. We know that the father must carry one copy of the A allele and one copy of the B allele.
Two punnett squares can answer this question, corresponding to the two possible maternal genotypes: one crossing AA x AB and the other crossing AO x AB. From the first cross there is a 50% chance of blood type A versus 50% chance of blood type AB (half AA and half AB). The second cross shows that there is a potential chance of 50% for type A, 25% for type AB, and 25% for type B (one AA, one OA, one AB, and one OB).
Based on these possibilities, the child could have blood type A, B, or AB. The child cannot have blood type O.
We are not given the mother's full genotype in the question; she could reasonably carry two A alleles, or an A allele and a recessive O allele. We know that the father must carry one copy of the A allele and one copy of the B allele.
Two punnett squares can answer this question, corresponding to the two possible maternal genotypes: one crossing AA x AB and the other crossing AO x AB. From the first cross there is a 50% chance of blood type A versus 50% chance of blood type AB (half AA and half AB). The second cross shows that there is a potential chance of 50% for type A, 25% for type AB, and 25% for type B (one AA, one OA, one AB, and one OB).
Based on these possibilities, the child could have blood type A, B, or AB. The child cannot have blood type O.
Compare your answer with the correct one above
A breeder performs a standard dihybrid cross between two plants that are heterozygous for both traits in question. How many unique genotypes could be present in the resulting offspring?
A breeder performs a standard dihybrid cross between two plants that are heterozygous for both traits in question. How many unique genotypes could be present in the resulting offspring?
There are nine distinct genotypes present after a standard dihybrid cross. This question can easily be answered by setting up a Punnett square (AaBb x AaBb) and counting the number of unique genotypes present after doing the cross. The numbers also conveniently work out that however many offspring display the dominant phenotype is equal to the number to of genotypes present (this is true for monohybrid and trihybrid crosses as well).
There are nine distinct genotypes present after a standard dihybrid cross. This question can easily be answered by setting up a Punnett square (AaBb x AaBb) and counting the number of unique genotypes present after doing the cross. The numbers also conveniently work out that however many offspring display the dominant phenotype is equal to the number to of genotypes present (this is true for monohybrid and trihybrid crosses as well).
Compare your answer with the correct one above
A scientist is performing a monohybrid homozygous cross: tall plants crossed with short plants. What fraction of the F2 generation are homozygous tall?
A scientist is performing a monohybrid homozygous cross: tall plants crossed with short plants. What fraction of the F2 generation are homozygous tall?
A monohybrid cross between two homozygous plants would involve a parental generation that looked like this: SS (tall) x ss (short). The F1 generation would produce only heterozygous tall plants (Ss). The F2 generation would produce offspring from the following cross: Ss x Ss. A punnett square would reveal that the F2 generation would have 25% homozygous tall (SS), 50% heterozygous tall (Ss), and 25% homozygous short plants. Note that we do not need information regarding which trait is dominant in this case, and we would still get the correct answer if we took short as the dominant phenotype.
A monohybrid cross between two homozygous plants would involve a parental generation that looked like this: SS (tall) x ss (short). The F1 generation would produce only heterozygous tall plants (Ss). The F2 generation would produce offspring from the following cross: Ss x Ss. A punnett square would reveal that the F2 generation would have 25% homozygous tall (SS), 50% heterozygous tall (Ss), and 25% homozygous short plants. Note that we do not need information regarding which trait is dominant in this case, and we would still get the correct answer if we took short as the dominant phenotype.
Compare your answer with the correct one above
In apple trees, the allele for white blossoms is dominant over the allele for pink blossoms. Two trees heterozygous for this gene are crossed. What is the phenotype ratio of the offspring?
In apple trees, the allele for white blossoms is dominant over the allele for pink blossoms. Two trees heterozygous for this gene are crossed. What is the phenotype ratio of the offspring?
The crossing of two heterozygous parents will yield 1 homozyougs dominant offspring, 1 homozygous recessive offspring and 2 heterozygous offspring. Since white blossoms is the dominant allele, the heterozygous offspring will be white leading to a phenotypic ratio of 3 white : 1 pink blossom.
The crossing of two heterozygous parents will yield 1 homozyougs dominant offspring, 1 homozygous recessive offspring and 2 heterozygous offspring. Since white blossoms is the dominant allele, the heterozygous offspring will be white leading to a phenotypic ratio of 3 white : 1 pink blossom.
Compare your answer with the correct one above
Assume complete dominance inheritance for the following question.
A pure-breeding red flower is mated with a pure-breeding white flower. All offspring are red in color; this is the F1 generation. Two of these offspring flowers are then mated with one another, and have F2 offspring.
Which of the following is true of the F2 offspring?
Assume complete dominance inheritance for the following question.
A pure-breeding red flower is mated with a pure-breeding white flower. All offspring are red in color; this is the F1 generation. Two of these offspring flowers are then mated with one another, and have F2 offspring.
Which of the following is true of the F2 offspring?
Since we had pure-breeding parents (also known as homozygotes for their respective colors), we can safely say the F1 offspring are heterozygotes and have a red allele and a white allele. When crossing these offspring with one another, we will expect to get a 3:1 ratio of red to white flowers. Not all flowers will be red, but 75% of the flowers will be.
Shown below is the punnett square that reflects this conclusion. (Note that "A" represents a red allele and "a" represents a white allele):
A a
A AA (red) Aa (red)
a Aa (red) aa (white)
Since we had pure-breeding parents (also known as homozygotes for their respective colors), we can safely say the F1 offspring are heterozygotes and have a red allele and a white allele. When crossing these offspring with one another, we will expect to get a 3:1 ratio of red to white flowers. Not all flowers will be red, but 75% of the flowers will be.
Shown below is the punnett square that reflects this conclusion. (Note that "A" represents a red allele and "a" represents a white allele):
A a
A AA (red) Aa (red)
a Aa (red) aa (white)
Compare your answer with the correct one above
In a species of ant, black coloration is dominant to white. A scientist is operating under the assumption that this gene follows basic Mendelian principles; however, after crossing two heterozygotes he obtained a ratio of 2:1 of dominant to recessive offspring. Which of the following could explain this result?
In a species of ant, black coloration is dominant to white. A scientist is operating under the assumption that this gene follows basic Mendelian principles; however, after crossing two heterozygotes he obtained a ratio of 2:1 of dominant to recessive offspring. Which of the following could explain this result?
The only answer that properly explains a 2:1 ratio is if the homozygous dominant phenotype is lethal. In our punnett square, this would give a two-thirds chance for a heterozygous offspring and a one-third chance for a recessive offspring. We know the recessive phenotype is not lethal because homozygous recessive offspring were produced.
Parents: Aa x Aa
Offspring genotypes: AA, Aa, Aa, aa
Offspring phenotypes: lethal, dominant, dominant, recessive (only three live offspring produced)
Offspring ratio: 2 dominant to 1 recessive
There is also no evidence that codominance or incomplete dominance is present. If black and white spotted offspring or gray offspring were produced then these theories would have merit.
The only answer that properly explains a 2:1 ratio is if the homozygous dominant phenotype is lethal. In our punnett square, this would give a two-thirds chance for a heterozygous offspring and a one-third chance for a recessive offspring. We know the recessive phenotype is not lethal because homozygous recessive offspring were produced.
Parents: Aa x Aa
Offspring genotypes: AA, Aa, Aa, aa
Offspring phenotypes: lethal, dominant, dominant, recessive (only three live offspring produced)
Offspring ratio: 2 dominant to 1 recessive
There is also no evidence that codominance or incomplete dominance is present. If black and white spotted offspring or gray offspring were produced then these theories would have merit.
Compare your answer with the correct one above
A scientist has been working with a new species of plant. He has found that there are two separate genes, which segregate according to standard Mendelian genetics, that are capable of producing the same phenotype. A single dominant allele from either gene confers red coloration of the plant's flowers. Without any dominant alleles the flowers are white. If he crosses two plants heterozygous for both traits, what will be the resulting phenotypic ratios of the offspring?
A scientist has been working with a new species of plant. He has found that there are two separate genes, which segregate according to standard Mendelian genetics, that are capable of producing the same phenotype. A single dominant allele from either gene confers red coloration of the plant's flowers. Without any dominant alleles the flowers are white. If he crosses two plants heterozygous for both traits, what will be the resulting phenotypic ratios of the offspring?
This problem requires a standard dihybrid cross. The crossed genotypes are AaBb x AaBb. This results in a phenotypic ratio of 9 dominant for both traits, 3 dominant for a single trait, 3 dominant for the other trait, and 1 recessive for both traits. In this cross, it will result in: 9 AxBx, 3 Axbb, 3 aaBx, and 1 aabb.
Since we know that the genes are both capable of making the red coloration we actually need to add together all of the choices that contain at least a single dominant allele. Essentially, AxBx, Axbb, and aaBx all show the exact same phenotype. This leaves us with a 15:1 ratio of red to white flowers.
This problem requires a standard dihybrid cross. The crossed genotypes are AaBb x AaBb. This results in a phenotypic ratio of 9 dominant for both traits, 3 dominant for a single trait, 3 dominant for the other trait, and 1 recessive for both traits. In this cross, it will result in: 9 AxBx, 3 Axbb, 3 aaBx, and 1 aabb.
Since we know that the genes are both capable of making the red coloration we actually need to add together all of the choices that contain at least a single dominant allele. Essentially, AxBx, Axbb, and aaBx all show the exact same phenotype. This leaves us with a 15:1 ratio of red to white flowers.
Compare your answer with the correct one above
A child is curious to know what his blood type is, but he only knows his parents' blood types. If his mother had blood type A and his father had blood type AB, what are the potential blood types the child might have?
A child is curious to know what his blood type is, but he only knows his parents' blood types. If his mother had blood type A and his father had blood type AB, what are the potential blood types the child might have?
We are not given the mother's full genotype in the question; she could reasonably carry two A alleles, or an A allele and a recessive O allele. We know that the father must carry one copy of the A allele and one copy of the B allele.
Two punnett squares can answer this question, corresponding to the two possible maternal genotypes: one crossing AA x AB and the other crossing AO x AB. From the first cross there is a 50% chance of blood type A versus 50% chance of blood type AB (half AA and half AB). The second cross shows that there is a potential chance of 50% for type A, 25% for type AB, and 25% for type B (one AA, one OA, one AB, and one OB).
Based on these possibilities, the child could have blood type A, B, or AB. The child cannot have blood type O.
We are not given the mother's full genotype in the question; she could reasonably carry two A alleles, or an A allele and a recessive O allele. We know that the father must carry one copy of the A allele and one copy of the B allele.
Two punnett squares can answer this question, corresponding to the two possible maternal genotypes: one crossing AA x AB and the other crossing AO x AB. From the first cross there is a 50% chance of blood type A versus 50% chance of blood type AB (half AA and half AB). The second cross shows that there is a potential chance of 50% for type A, 25% for type AB, and 25% for type B (one AA, one OA, one AB, and one OB).
Based on these possibilities, the child could have blood type A, B, or AB. The child cannot have blood type O.
Compare your answer with the correct one above
A breeder performs a standard dihybrid cross between two plants that are heterozygous for both traits in question. How many unique genotypes could be present in the resulting offspring?
A breeder performs a standard dihybrid cross between two plants that are heterozygous for both traits in question. How many unique genotypes could be present in the resulting offspring?
There are nine distinct genotypes present after a standard dihybrid cross. This question can easily be answered by setting up a Punnett square (AaBb x AaBb) and counting the number of unique genotypes present after doing the cross. The numbers also conveniently work out that however many offspring display the dominant phenotype is equal to the number to of genotypes present (this is true for monohybrid and trihybrid crosses as well).
There are nine distinct genotypes present after a standard dihybrid cross. This question can easily be answered by setting up a Punnett square (AaBb x AaBb) and counting the number of unique genotypes present after doing the cross. The numbers also conveniently work out that however many offspring display the dominant phenotype is equal to the number to of genotypes present (this is true for monohybrid and trihybrid crosses as well).
Compare your answer with the correct one above
A scientist is performing a monohybrid homozygous cross: tall plants crossed with short plants. What fraction of the F2 generation are homozygous tall?
A scientist is performing a monohybrid homozygous cross: tall plants crossed with short plants. What fraction of the F2 generation are homozygous tall?
A monohybrid cross between two homozygous plants would involve a parental generation that looked like this: SS (tall) x ss (short). The F1 generation would produce only heterozygous tall plants (Ss). The F2 generation would produce offspring from the following cross: Ss x Ss. A punnett square would reveal that the F2 generation would have 25% homozygous tall (SS), 50% heterozygous tall (Ss), and 25% homozygous short plants. Note that we do not need information regarding which trait is dominant in this case, and we would still get the correct answer if we took short as the dominant phenotype.
A monohybrid cross between two homozygous plants would involve a parental generation that looked like this: SS (tall) x ss (short). The F1 generation would produce only heterozygous tall plants (Ss). The F2 generation would produce offspring from the following cross: Ss x Ss. A punnett square would reveal that the F2 generation would have 25% homozygous tall (SS), 50% heterozygous tall (Ss), and 25% homozygous short plants. Note that we do not need information regarding which trait is dominant in this case, and we would still get the correct answer if we took short as the dominant phenotype.
Compare your answer with the correct one above
In apple trees, the allele for white blossoms is dominant over the allele for pink blossoms. Two trees heterozygous for this gene are crossed. What is the phenotype ratio of the offspring?
In apple trees, the allele for white blossoms is dominant over the allele for pink blossoms. Two trees heterozygous for this gene are crossed. What is the phenotype ratio of the offspring?
The crossing of two heterozygous parents will yield 1 homozyougs dominant offspring, 1 homozygous recessive offspring and 2 heterozygous offspring. Since white blossoms is the dominant allele, the heterozygous offspring will be white leading to a phenotypic ratio of 3 white : 1 pink blossom.
The crossing of two heterozygous parents will yield 1 homozyougs dominant offspring, 1 homozygous recessive offspring and 2 heterozygous offspring. Since white blossoms is the dominant allele, the heterozygous offspring will be white leading to a phenotypic ratio of 3 white : 1 pink blossom.
Compare your answer with the correct one above