Understanding Mendel - AP Biology
Card 1 of 252
Gregor Mendel’s major contribution to the study of inheritance was to show that .
Gregor Mendel’s major contribution to the study of inheritance was to show that .
Tap to reveal answer
Gregor Mendel's famous work on pea plants built our first understandings of inheritance. He identified that "discrete particles", which we now call genes and alleles, are passed to offspring in numerous of combinations. These different combinations create variation in a population.
Gregor Mendel's famous work on pea plants built our first understandings of inheritance. He identified that "discrete particles", which we now call genes and alleles, are passed to offspring in numerous of combinations. These different combinations create variation in a population.
← Didn't Know|Knew It →
What concept did Gregor Mendel contribute to biology?
What concept did Gregor Mendel contribute to biology?
Tap to reveal answer
Mendel is considered the father of modern genetics and did extensive research on genetic heritability, alleles, and inheritance. His main research was performed on drosophila (flies) and pea plants. Mendel's discoveries helped shape our understanding of how genes are inherited and expressed. One of his theories outlines the idea that chromosomes do not align by paternal and maternal segregation during tetrad formation in meiosis, but are organized independent of their parental origin. This theory is known as the Principle of Independent Assortment.
The Law of Population Genetics was developed by Hardy and Weinberg. Charles Darwin created the Theory of Evolution. Lamarck created the Postulate of Inheritance of Acquired Traits.
Mendel is considered the father of modern genetics and did extensive research on genetic heritability, alleles, and inheritance. His main research was performed on drosophila (flies) and pea plants. Mendel's discoveries helped shape our understanding of how genes are inherited and expressed. One of his theories outlines the idea that chromosomes do not align by paternal and maternal segregation during tetrad formation in meiosis, but are organized independent of their parental origin. This theory is known as the Principle of Independent Assortment.
The Law of Population Genetics was developed by Hardy and Weinberg. Charles Darwin created the Theory of Evolution. Lamarck created the Postulate of Inheritance of Acquired Traits.
← Didn't Know|Knew It →
Mendel originally proposed the idea of a "factor" that controls phenotype and comes in a recessive and a dominant form. Which of the following modern terms most aptly describe Mendel's "factors"?
Mendel originally proposed the idea of a "factor" that controls phenotype and comes in a recessive and a dominant form. Which of the following modern terms most aptly describe Mendel's "factors"?
Tap to reveal answer
Mendel's "factors" are today's genes. From his limited knowledge of cell biology, Mendel was able to observe the effects of genes by observing phenotype. Genes come in multiple forms, known today as alleles, which control dominant and recessive inheritance.
Chromatin is the term used to describe DNA packaged by proteins. Centromeres are the area of chromosomes where sister chromatids are attached. Chromosomes would not be an acceptable description of a "factor" because it is the specific gene that controls the phenotype, not the entire chromosome.
Mendel's "factors" are today's genes. From his limited knowledge of cell biology, Mendel was able to observe the effects of genes by observing phenotype. Genes come in multiple forms, known today as alleles, which control dominant and recessive inheritance.
Chromatin is the term used to describe DNA packaged by proteins. Centromeres are the area of chromosomes where sister chromatids are attached. Chromosomes would not be an acceptable description of a "factor" because it is the specific gene that controls the phenotype, not the entire chromosome.
← Didn't Know|Knew It →
Which of the following is NOT a reason that Gregor Mendel chose to work with pea plants?
Which of the following is NOT a reason that Gregor Mendel chose to work with pea plants?
Tap to reveal answer
Pea plants reproduce quickly and in large numbers. They can self-pollinate within a single plant, they can be cross-pollinated by insection, and they can be selectively cross-pollinated using a tool such as a cotton swab. Pea plants contain separate male and female parts, but each plant contains both. Sex-linked traits cannot be studied in organisms that do not have clearly separate male and female members. Phenotypically, there are no male and female members of the pea plant species, making it impossible to track traits that follow sex-linked expression.
Pea plants reproduce quickly and in large numbers. They can self-pollinate within a single plant, they can be cross-pollinated by insection, and they can be selectively cross-pollinated using a tool such as a cotton swab. Pea plants contain separate male and female parts, but each plant contains both. Sex-linked traits cannot be studied in organisms that do not have clearly separate male and female members. Phenotypically, there are no male and female members of the pea plant species, making it impossible to track traits that follow sex-linked expression.
← Didn't Know|Knew It →
Which of the given disorders follows classical Mendelian inheritance?
Which of the given disorders follows classical Mendelian inheritance?
Tap to reveal answer
Cystic fibrosis occurs in individuals who are homozygous recessive for a single gene, following Mendelian inheritance patterns.
Down Syndrome is caused by a trisomy and is not conferred via a specific allele. The disorder is the result of a nondisjunction event during meiosis. Fragile X Syndrome occurs when a portion of the X-chromosome in men is extended due to dozens or hundreds of repeats. The number of repeats changes between generations, making this non-Mendelian. Type I diabetes is most often caused by a poorly understood autoimmune condition, wherein the immune system attacks the cells in the pancreas responsible for insulin production. The underlying autoimmune response is thought to be partially genetic and partially environmental.
Cystic fibrosis occurs in individuals who are homozygous recessive for a single gene, following Mendelian inheritance patterns.
Down Syndrome is caused by a trisomy and is not conferred via a specific allele. The disorder is the result of a nondisjunction event during meiosis. Fragile X Syndrome occurs when a portion of the X-chromosome in men is extended due to dozens or hundreds of repeats. The number of repeats changes between generations, making this non-Mendelian. Type I diabetes is most often caused by a poorly understood autoimmune condition, wherein the immune system attacks the cells in the pancreas responsible for insulin production. The underlying autoimmune response is thought to be partially genetic and partially environmental.
← Didn't Know|Knew It →
Which of the following is the most accurate definition of an allele?
Which of the following is the most accurate definition of an allele?
Tap to reveal answer
Genes are determined by sequences of DNA that code for certain proteins. Sometimes, mutations to the gene can result in a modified protein that maintains the same or similar functions as the original. When this modified gene is passed down, it is known as an allele. Most accurately, an allele is a variation of a given gene.
Most alleles can be considered dominant or recessive, with respect to one another; however, instances of codominance and incomplete dominance mean that there is a spectrum of dominance. Defining all alleles by these parameters is not very accurate. Some alleles code for wild genotypes, while others code for mutated genotypes. Recombination is the transfer of genetic material between homologous chromosomes, and does not result in new alleles. New alleles require a mutation event in order to increase genetic diversity.
Genes are determined by sequences of DNA that code for certain proteins. Sometimes, mutations to the gene can result in a modified protein that maintains the same or similar functions as the original. When this modified gene is passed down, it is known as an allele. Most accurately, an allele is a variation of a given gene.
Most alleles can be considered dominant or recessive, with respect to one another; however, instances of codominance and incomplete dominance mean that there is a spectrum of dominance. Defining all alleles by these parameters is not very accurate. Some alleles code for wild genotypes, while others code for mutated genotypes. Recombination is the transfer of genetic material between homologous chromosomes, and does not result in new alleles. New alleles require a mutation event in order to increase genetic diversity.
← Didn't Know|Knew It →
A parent plant that is homozygous for the yellow color allele is crossed with a plant that is homozygous for the green allele. If all F1 offspring are yellow, what can be concluded about the cross?
A parent plant that is homozygous for the yellow color allele is crossed with a plant that is homozygous for the green allele. If all F1 offspring are yellow, what can be concluded about the cross?
Tap to reveal answer
If both parents are homozygous and the F1 generation only resembles one of the parents, then that parent must have been homozygous for the dominant gene. This means that the yellow plant has genes that are dominant over the green plant, making all offspring yellow.
Parents: AA (yellow) x aa (green)
Offspring: all Aa (yellow)
All of the offspring will be heterozygous and show the dominant phenotype (yellow).
A test-cross would cross the F1 offspring with a homozygous recessive individual. The result would be half Aa (yellow) and half aa (green) offspring.
If both parents are homozygous and the F1 generation only resembles one of the parents, then that parent must have been homozygous for the dominant gene. This means that the yellow plant has genes that are dominant over the green plant, making all offspring yellow.
Parents: AA (yellow) x aa (green)
Offspring: all Aa (yellow)
All of the offspring will be heterozygous and show the dominant phenotype (yellow).
A test-cross would cross the F1 offspring with a homozygous recessive individual. The result would be half Aa (yellow) and half aa (green) offspring.
← Didn't Know|Knew It →
If two heterozygous yellow plants are mated with one another, what percent of the offspring will be green?
If two heterozygous yellow plants are mated with one another, what percent of the offspring will be green?
Tap to reveal answer
Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the dominant phenotype. If the heterozygous plants in the question are yellow, then we can conclude that yellow is dominant to green.
The cross for these two plants would be:
Parents: Yy x Yy
Offspring: YY (yellow), Yy (yellow), Yy (yellow), yy (green)
Of four possible offspring, one will be green, leading to the answer: 25%.
Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the dominant phenotype. If the heterozygous plants in the question are yellow, then we can conclude that yellow is dominant to green.
The cross for these two plants would be:
Parents: Yy x Yy
Offspring: YY (yellow), Yy (yellow), Yy (yellow), yy (green)
Of four possible offspring, one will be green, leading to the answer: 25%.
← Didn't Know|Knew It →
The trait for tall pea plants is dominant to the trait for short pea plants. Which of the following experimental set-ups could be used to prove this conclusion?
The trait for tall pea plants is dominant to the trait for short pea plants. Which of the following experimental set-ups could be used to prove this conclusion?
Tap to reveal answer
A test-cross is used to determine the genotypes of unknown organisms, but can also be valuable to distinguish dominant and recessive traits. A test-cross is when an unknown organism is crossed with a homozygous recessive organism. If the unknown organism is homozygous dominant, then all offspring will show the dominant phenotype.
Crossing an homozygous tall plant with a homozygous short plant, and observing all tall offspring, would prove that the tall trait is dominant.
One answer option suggests crossing a homozygous tall plant with a heterozygous short plant; this is impossible because all heterozygotes will show the tall phenotype. The remaining two answers will result in some combination of tall and short offspring. Though the ratios of the offspring phenotypes could be helpful in confirming that the tall trait is dominant, a test-cross is more useful and more definite.
A test-cross is used to determine the genotypes of unknown organisms, but can also be valuable to distinguish dominant and recessive traits. A test-cross is when an unknown organism is crossed with a homozygous recessive organism. If the unknown organism is homozygous dominant, then all offspring will show the dominant phenotype.
Crossing an homozygous tall plant with a homozygous short plant, and observing all tall offspring, would prove that the tall trait is dominant.
One answer option suggests crossing a homozygous tall plant with a heterozygous short plant; this is impossible because all heterozygotes will show the tall phenotype. The remaining two answers will result in some combination of tall and short offspring. Though the ratios of the offspring phenotypes could be helpful in confirming that the tall trait is dominant, a test-cross is more useful and more definite.
← Didn't Know|Knew It →
Two pea plants are heterozygous for the gene coding for seed color. If these plants are crossed, what percentage of the offspring will show the dominant phenotype?
Two pea plants are heterozygous for the gene coding for seed color. If these plants are crossed, what percentage of the offspring will show the dominant phenotype?
Tap to reveal answer
For this question we are not given any information about dominant and recessive phenotypes. We know only that we are working with two heterozygous plants. Using only this information, we can determine the genotypes of the offspring.
Parents: Hh (dominant) x Hh (dominant)
Offspring: HH (dominant), Hh (dominant), Hh (dominant), hh (recessive)
We do not know if the plants will be tall or short, but we know that three of the four offspring will show the dominant phenotype. This leads to the answer of 75%.
For this question we are not given any information about dominant and recessive phenotypes. We know only that we are working with two heterozygous plants. Using only this information, we can determine the genotypes of the offspring.
Parents: Hh (dominant) x Hh (dominant)
Offspring: HH (dominant), Hh (dominant), Hh (dominant), hh (recessive)
We do not know if the plants will be tall or short, but we know that three of the four offspring will show the dominant phenotype. This leads to the answer of 75%.
← Didn't Know|Knew It →
A heterozygous plant with green peas is crossed with a plant with yellow peas. What percent of the offspring will be yellow?
A heterozygous plant with green peas is crossed with a plant with yellow peas. What percent of the offspring will be yellow?
Tap to reveal answer
Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the dominant phenotype. If the heterozygous plant in the question has green peas, then we can conclude that green peas are dominant to yellow peas. The yellow pea plant must be homozygous recessive.
The cross for these two plants would be:
Parents: Pp (green) x pp (yellow)
Offspring: half Pp (green) and half pp (yellow)
Half of the offspring will be heterozygous, displaying the dominant green phenotype, and half will be homozygous recessive, displaying the recessive yellow phenotype.
Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the dominant phenotype. If the heterozygous plant in the question has green peas, then we can conclude that green peas are dominant to yellow peas. The yellow pea plant must be homozygous recessive.
The cross for these two plants would be:
Parents: Pp (green) x pp (yellow)
Offspring: half Pp (green) and half pp (yellow)
Half of the offspring will be heterozygous, displaying the dominant green phenotype, and half will be homozygous recessive, displaying the recessive yellow phenotype.
← Didn't Know|Knew It →
There are two alleles for fur color in a population of mice: white and black. If these alleles demonstrate incomplete dominance, what is the expected phenotypic ratio of offspring generated from a cross of two heterozygous parents?
There are two alleles for fur color in a population of mice: white and black. If these alleles demonstrate incomplete dominance, what is the expected phenotypic ratio of offspring generated from a cross of two heterozygous parents?
Tap to reveal answer
We are told that the two parents are heterozygous. This allows us to set up the given cross fairly easily.
Parents: Aa x Aa
Offspring: AA, Aa, Aa, aa
Now, however, we need to determine the phenotypes of these offspring. Since the alleles exhibit incomplete dominance it is irrelevant which allele is represented by A and which is represented by a. AA will show one extreme phenotype, aa will show the other extreme phenotype, and Aa will show an intermediate blended phenotype. In this case, the phenotypic ratio will be 1 black (AA) : 2 gray (Aa) : 1 white (aa).
We are told that the two parents are heterozygous. This allows us to set up the given cross fairly easily.
Parents: Aa x Aa
Offspring: AA, Aa, Aa, aa
Now, however, we need to determine the phenotypes of these offspring. Since the alleles exhibit incomplete dominance it is irrelevant which allele is represented by A and which is represented by a. AA will show one extreme phenotype, aa will show the other extreme phenotype, and Aa will show an intermediate blended phenotype. In this case, the phenotypic ratio will be 1 black (AA) : 2 gray (Aa) : 1 white (aa).
← Didn't Know|Knew It →
If two heterozygous yellow plants are mated with one another, what percent of the offspring will be yellow? Assume complete dominance.
If two heterozygous yellow plants are mated with one another, what percent of the offspring will be yellow? Assume complete dominance.
Tap to reveal answer
Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the dominant phenotype. If the heterozygous plants in the question are yellow, then we can conclude that yellow is dominant to some other phenotype (not given).
The cross for these two plants would be:
Parents: Yy (yellow) x Yy (yellow)
Offspring: YY (yellow), Yy (yellow), Yy (yellow), yy (other/unknown)
Three of the four possible offspring will show the dominant yellow phenotype, leading to the answer: 75%.
Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the dominant phenotype. If the heterozygous plants in the question are yellow, then we can conclude that yellow is dominant to some other phenotype (not given).
The cross for these two plants would be:
Parents: Yy (yellow) x Yy (yellow)
Offspring: YY (yellow), Yy (yellow), Yy (yellow), yy (other/unknown)
Three of the four possible offspring will show the dominant yellow phenotype, leading to the answer: 75%.
← Didn't Know|Knew It →
A student selects a random pea plant from Mendel's garden. She notes that the plant has red leaves, but all other plants in the garden have green leaves. She presents the plant to Mendel, who claims that he has never seen a plant with red leaves before. What phenomenon is most likely responsible for the red leaf phenotype?
A student selects a random pea plant from Mendel's garden. She notes that the plant has red leaves, but all other plants in the garden have green leaves. She presents the plant to Mendel, who claims that he has never seen a plant with red leaves before. What phenomenon is most likely responsible for the red leaf phenotype?
Tap to reveal answer
The red leaf phenotype represents a new allele in the population. None of the other plants have this trait and there are no other known red-leaf plants in the region. Most likely, the new phenotype is the result of a mutation. All alleles start as mutations and spread as the mutation is inherited by more individuals in the population.
Recombination (crossing over) can result in new combinations of existing alleles, but cannot create new traits. Incomplete dominance can result in an unpredicted phenotype, but will be present in all organisms with a heterozygous phenotype. It would be highly unlikely that all other plants in the population were homozygotes. Though there is an extraordinarily small chance that the red leaves result from a recessive allele, this is not likely the case considering the sample size.
The red leaf phenotype represents a new allele in the population. None of the other plants have this trait and there are no other known red-leaf plants in the region. Most likely, the new phenotype is the result of a mutation. All alleles start as mutations and spread as the mutation is inherited by more individuals in the population.
Recombination (crossing over) can result in new combinations of existing alleles, but cannot create new traits. Incomplete dominance can result in an unpredicted phenotype, but will be present in all organisms with a heterozygous phenotype. It would be highly unlikely that all other plants in the population were homozygotes. Though there is an extraordinarily small chance that the red leaves result from a recessive allele, this is not likely the case considering the sample size.
← Didn't Know|Knew It →
The color trait for flowers shows incomplete dominance. If a heterozygous plant with pink flowers is mated with a homozygous plant with red flowers, what percent of the offspring will have white flowers?
The color trait for flowers shows incomplete dominance. If a heterozygous plant with pink flowers is mated with a homozygous plant with red flowers, what percent of the offspring will have white flowers?
Tap to reveal answer
Incomplete dominance results in phenotypic blending in heterozygous organisms. In this example, homozygous flowers will be either white or red, and heterozygous flowers will be pink.
We can determine the outcome of this cross by looking at the parental genotypes:
Parents: Pp (pink) x PP (red)
Offspring: half Pp (pink) and half PP (red)
Half of the offspring will be heterozygous, showing the pink phenotype, and half will be homozygous for the red allele. None of the offspring will be homozygous for the white allele.
Incomplete dominance results in phenotypic blending in heterozygous organisms. In this example, homozygous flowers will be either white or red, and heterozygous flowers will be pink.
We can determine the outcome of this cross by looking at the parental genotypes:
Parents: Pp (pink) x PP (red)
Offspring: half Pp (pink) and half PP (red)
Half of the offspring will be heterozygous, showing the pink phenotype, and half will be homozygous for the red allele. None of the offspring will be homozygous for the white allele.
← Didn't Know|Knew It →
Which of the following principles is credited to Mendel?
Which of the following principles is credited to Mendel?
Tap to reveal answer
Mendel's work focused heavily on identifying mechanisms and patterns in genetic inheritance. He is credited with three essential laws: the law of segregation, the law of independent assortment, and the law of dominance.
The law of segregation states that a parent organism will pass only one copy of each allele to its offspring. No parent will pass two copies of the same gene. The law of independent assortment states that the alleles to be passed down are not linked by past modes of inheritance, and will separate independent of one another. The law of dominance simply states that dominant traits will mask recessive traits.
The law of natural selection is credited to Charles Darwin for is work in evolution. The law of genetic variability and the law of diploidy are not recognized scientific principles.
Mendel's work focused heavily on identifying mechanisms and patterns in genetic inheritance. He is credited with three essential laws: the law of segregation, the law of independent assortment, and the law of dominance.
The law of segregation states that a parent organism will pass only one copy of each allele to its offspring. No parent will pass two copies of the same gene. The law of independent assortment states that the alleles to be passed down are not linked by past modes of inheritance, and will separate independent of one another. The law of dominance simply states that dominant traits will mask recessive traits.
The law of natural selection is credited to Charles Darwin for is work in evolution. The law of genetic variability and the law of diploidy are not recognized scientific principles.
← Didn't Know|Knew It →
Gregor Mendel, an Augustinian friar, studied genetics through what types of experiments?
Gregor Mendel, an Augustinian friar, studied genetics through what types of experiments?
Tap to reveal answer
Gregor Mendel studied genetics through the crossbreeding of pea plants. Through his studies, he proposed laws of heredity (the law of segregation, the law of independent assortment, and the law of dominance), that are now called the laws of Mendelian inheritance. Darwin famously studied finches on the Galapagos Islands.
Gregor Mendel studied genetics through the crossbreeding of pea plants. Through his studies, he proposed laws of heredity (the law of segregation, the law of independent assortment, and the law of dominance), that are now called the laws of Mendelian inheritance. Darwin famously studied finches on the Galapagos Islands.
← Didn't Know|Knew It →
Which of the following concepts was not discovered by the scientist Gregor Mendel?
Which of the following concepts was not discovered by the scientist Gregor Mendel?
Tap to reveal answer
The overall idea that Mendel was studying was that organisms have two alleles per trait, and that each parent passes down one allele. The other answers refer to Mendel’s laws: the Law of Segregation, the Law of Independent Assortment, and the Law of Dominance. Mendel was unaware of genetic linkage, which is an exception to the Law of Independent Assortment. We know this to be true because chromosomes and DNA had not yet been discovered in his time.
The overall idea that Mendel was studying was that organisms have two alleles per trait, and that each parent passes down one allele. The other answers refer to Mendel’s laws: the Law of Segregation, the Law of Independent Assortment, and the Law of Dominance. Mendel was unaware of genetic linkage, which is an exception to the Law of Independent Assortment. We know this to be true because chromosomes and DNA had not yet been discovered in his time.
← Didn't Know|Knew It →
Gregor Mendel’s major contribution to the study of inheritance was to show that .
Gregor Mendel’s major contribution to the study of inheritance was to show that .
Tap to reveal answer
Gregor Mendel's famous work on pea plants built our first understandings of inheritance. He identified that "discrete particles", which we now call genes and alleles, are passed to offspring in numerous of combinations. These different combinations create variation in a population.
Gregor Mendel's famous work on pea plants built our first understandings of inheritance. He identified that "discrete particles", which we now call genes and alleles, are passed to offspring in numerous of combinations. These different combinations create variation in a population.
← Didn't Know|Knew It →
What concept did Gregor Mendel contribute to biology?
What concept did Gregor Mendel contribute to biology?
Tap to reveal answer
Mendel is considered the father of modern genetics and did extensive research on genetic heritability, alleles, and inheritance. His main research was performed on drosophila (flies) and pea plants. Mendel's discoveries helped shape our understanding of how genes are inherited and expressed. One of his theories outlines the idea that chromosomes do not align by paternal and maternal segregation during tetrad formation in meiosis, but are organized independent of their parental origin. This theory is known as the Principle of Independent Assortment.
The Law of Population Genetics was developed by Hardy and Weinberg. Charles Darwin created the Theory of Evolution. Lamarck created the Postulate of Inheritance of Acquired Traits.
Mendel is considered the father of modern genetics and did extensive research on genetic heritability, alleles, and inheritance. His main research was performed on drosophila (flies) and pea plants. Mendel's discoveries helped shape our understanding of how genes are inherited and expressed. One of his theories outlines the idea that chromosomes do not align by paternal and maternal segregation during tetrad formation in meiosis, but are organized independent of their parental origin. This theory is known as the Principle of Independent Assortment.
The Law of Population Genetics was developed by Hardy and Weinberg. Charles Darwin created the Theory of Evolution. Lamarck created the Postulate of Inheritance of Acquired Traits.
← Didn't Know|Knew It →