122 Questions
What is the main limitation of the 'blending' hypothesis of inheritance?
It fails to explain how traits can reappear after they've skipped a generation.
What is the analogy used to describe the particulate hypothesis of inheritance?
A deck of cards
What is the term used to describe the discrete heritable units that are passed on from parents to offspring?
Genes
Where did the monk named Gregor Mendel develop his theory of inheritance?
An abbey garden
What is the outcome of the blending hypothesis of inheritance over many generations?
A uniform population of individuals
What is the main difference between the blending hypothesis and the particulate hypothesis of inheritance?
The particulate hypothesis assumes that genetic material mixes together
Why did Mendel choose to work with peas in his experiments?
Because there are many varieties with distinct characteristics
What is the term for a heritable feature that varies among individuals?
Character
How did Mendel achieve cross-pollination between two plants?
By removing the stamens of one plant and dusting pollen from another onto the altered flowers
What is the term for the first generation of offspring from a cross between two true-breeding varieties?
F1 generation
What was the primary reason why Mendel failed to become a teacher?
He failed the necessary examination
What is the term for a plant that produces only one variety of offspring through self-pollination?
True-breeding
Which of the following was NOT a part of Mendel's education?
Medical training
Why did Mendel follow traits for at least the P, F1, and F2 generations?
To understand the principles of inheritance
What was the significance of Mendel's two years of study at the University of Vienna?
It was where he was trained to use mathematics to explain natural phenomena
What was the approximate ratio of purple to white flowers in the F2 generation?
3:1
What was the occupation of Mendel's parents?
Farmers
What is the outcome of the experiment when Mendel crossed purple-flowered and white-flowered pea plants?
The F1 hybrids had purple flowers
Who was the physicist that influenced Mendel's approach to science?
Christian Doppler
What is the term used to describe the heritable factor for white flowers?
Recessive trait
What did Mendel's quantitative analysis of the F2 plants reveal?
The principles of inheritance
What was the primary focus of Mendel's experiments?
Breeding garden peas
What is the term used to describe the different versions of a gene?
Alleles
Why did Mendel choose to track only those characters that occurred in two distinct, alternative forms?
Because it allowed him to study the principles of inheritance more accurately
What was the reason why Mendel entered an Augustinian monastery?
He valued the life of the mind
How many copies of a gene does an organism inherit?
Two
What is the term for the process of crossing two true-breeding varieties?
Hybridization
What determines the organism's appearance when the two alleles at a locus differ?
Dominant allele
What was the outcome of Mendel's carefully planned experiments?
He identified two laws of inheritance
What is the term used to describe the physical location of a gene on a chromosome?
Locus
What is the outcome of self- or cross-pollination of F1 plants?
A mix of purple- and white-flowered offspring
What is the term used to describe the first generation of offspring?
F1 generation
What is the term used to describe the process of hiding or masking of one trait by another?
Dominance
What is the name of the law that Mendel developed to explain the 3:1 inheritance pattern?
Law of Segregation
What is the term used to describe an organism's observable traits?
Phenotype
What is the purpose of a testcross?
To determine the genotype of an organism
What is the term used to describe individuals heterozygous for two characters being followed in a cross?
Dihybrid
Why do PP and Pp plants have the same phenotype?
Because they have different genotypes but the same dominant allele
What is the law that describes the transmission of two characters as independent units?
Law of Independent Assortment
What is the genotype of a plant with yellow-round seeds?
YYRR
What is the phenomenon described in the law of segregation?
The separation of two alleles into different gametes
What is the prediction of Mendel's segregation model for the flower-color character in the F2 generation?
Three-fourth of the plants will have purple flowers and one-fourth will have white flowers
What is the purpose of a dihybrid cross?
To study the inheritance of two characters
What is the term used to describe an organism that has two different alleles for a gene?
Heterozygote
What is the expected ratio of phenotypes in the offspring of a Pp * pp cross?
1:1
Why is it difficult to determine the genotype of a purple-flowered pea plant?
Because it can be homozygous or heterozygous
What is the characteristic of true-breeding plants?
All their gametes contain the same allele
What is the purpose of a Punnett square?
To predict the allele composition of offspring from a cross between individuals of known genetic makeup
What is the genotype of a plant with green-wrinkled seeds?
yyrr
What is the ratio of traits observed in the F2 generation of Mendel's experiment?
3:1
What is the term used to describe an organism that has a pair of identical alleles for a gene?
Homozygote
What is the genotype of an F1 hybrid?
Pp
What is the result of self-pollination of F1 hybrids?
Both purple-flowered and white-flowered offspring
What is the symbol used to represent the dominant allele in the flower-color character?
P
What is the predicted phenotypic ratio of the F2 generation according to the dependent assortment hypothesis?
3:1
How many equally probable ways can the alleles combine in the F2 generation, according to the independent assortment hypothesis?
16
What is the result of Mendel's dihybrid experiments?
A 9:3:3:1 phenotypic ratio in the F2 generation
What is the law of independent assortment?
The law that states that two or more genes assort independently during gamete formation
Why did Mendel choose pea characters for his analysis?
Because they were controlled by genes on different chromosomes or far apart on the same chromosome
What is the result of counting the number of yellow and green peas, ignoring shape, in Mendel's dihybrid experiments?
A 3:1 phenotypic ratio
What is the analogy used to describe the law of independent assortment?
A coin toss
What is the condition for the law of independent assortment to apply?
The genes are located on different chromosomes or are far apart on the same chromosome
What is the significance of Mendel's dihybrid experiments?
They supported the law of independent assortment
What is the relationship between the alleles of one gene and the alleles of another gene during gamete formation?
They segregate into gametes independently of each other
What is the predicted phenotypic ratio in the F2 generation according to the 'dependent assortment' hypothesis?
3:1
What is the basis for the law of independent assortment?
Mendel's dihybrid experiments
What is the significance of the testcross in Mendel's experiments?
To reveal the genotype of an organism of unknown genotype
What is the term for an organism's observable traits?
Phenotype
What is the assumption behind the independent segregation of alleles in a dihybrid cross?
Each gene is located on a different chromosome
What is the purpose of a dihybrid cross?
To study the inheritance of two characters simultaneously
What is the purpose of counting the number of yellow and green peas in a dihybrid experiment?
To compare the results to the monohybrid cross
What is the expected ratio of phenotypes in the offspring of a Pp * pp cross?
1:1
What is the key difference between the law of independent assortment and the law of segregation?
The law of segregation describes the transmission of one character, while the law of independent assortment describes the transmission of two characters
What is the law that describes the transmission of two characters as independent units?
The Law of Independent Assortment
What is the significance of the 9:3:3:1 phenotypic ratio in the F2 generation?
It indicates that the genes are independent
Why did Mendel choose to study pea characters that occurred in two distinct, alternative forms?
To simplify the interpretation of his results
What is the term for individuals heterozygous for two characters being followed in a cross?
Dihybrid
Why do PP and Pp plants have the same phenotype?
Because the dominant allele masks the effect of the recessive allele
What is the analogy used to describe the law of independent assortment?
The analogy of a coin toss
What is the purpose of a monohybrid cross?
To study the inheritance of a single character
What is the key principle underlying the law of independent assortment?
Each pair of alleles segregates independently of any other pair of alleles
What is the significance of the 3:1 phenotypic ratio in the F2 generation of a monohybrid cross?
It supports the particulate hypothesis of inheritance
What is the genotype of a plant with yellow-round seeds?
YYRR
Why is it difficult to determine the genotype of a purple-flowered pea plant?
Because it can be either homozygous or heterozygous
What was the main influence on Mendel's development as a scientist during his two years of study at the University of Vienna?
Christian Doppler's encouragement of experimentation
What was the primary reason why Mendel's work was not widely recognized during his lifetime?
He failed to publish his results
What was the outcome of Mendel's careful planning and execution of his experiments?
He developed a new theory of inheritance
What was the significance of Mendel's childhood and education?
He learned to value the life of the mind
What was the primary focus of Mendel's experiments in his garden?
To develop a new theory of inheritance
What did Mendel's quantitative analysis of the F2 plants reveal?
The particulate hypothesis of inheritance
What was the primary reason why Mendel chose to work with garden peas in his experiments?
They were easy to breed and cross-pollinate
What was the significance of Christian Doppler's influence on Mendel's approach to science?
He taught Mendel to use mathematics to explain natural phenomena
What is the advantage of using peas in Mendel's experiments?
They have many varieties and a short generation time
What is the reason why the F1 plants have purple flowers?
Because the allele for purple flowers is dominant
Why did Mendel remove the immature stamens of a plant before they produced pollen?
To achieve cross-pollination of two plants
What happens during gamete formation according to the law of segregation?
The two alleles for a heritable character segregate and end up in different gametes
What is the term for the hybrid offspring of two true-breeding varieties?
F1 generation
What is the significance of the F2 generation in Mendel's experiments?
It allows for the study of inheritance patterns
What is the prediction of Mendel's segregation model for the flower-color character in the F2 generation?
One-fourth of the F2 plants will have purple flowers, one-half will have a combination of purple and white flowers, and one-fourth will have white flowers
What is the result of crossing purple-flowered and white-flowered pea plants?
All offspring have purple flowers
What is the term for an organism that has two different alleles for a gene?
Heterozygote
What is the purpose of a Punnett square?
To predict the allele composition of offspring
Why did Mendel track only those characters that occurred in two distinct, alternative forms?
To make his experiments more straightforward
What is the ratio of traits observed in the F2 generation of Mendel's experiment?
3:1
What is the term for a plant that produces only one variety of offspring through self-pollination?
True-breeding
What determines the organism's appearance when the two alleles at a locus differ?
The dominant allele
What is the purpose of allowing F1 hybrids to self-pollinate or cross-pollinate with other F1 hybrids?
To produce the F2 generation
What is the term for a plant that produces only one variety of offspring through self-pollination?
True-breeding
What is the significance of Mendel's quantitative analysis of the F2 plants?
It allowed him to deduce the laws of inheritance
What is the term for the process of crossing two true-breeding varieties?
Hybridization
What is the outcome of self-pollination of F1 plants?
Both purple-flowered and white-flowered offspring will be produced
What is the term for the physical location of a gene on a chromosome?
Locus
What is the reason why the white-flower trait reappeared in the F2 generation?
The heritable factor for white flowers was hidden in the F1 plants
What is the term used to describe the gene that allows synthesis of purple pigment in pea plants?
Purple-flower allele
What is the result of the cross-pollination between a true-breeding variety that produces smooth, round pea seeds and one that produces wrinkled seeds?
All F1 hybrids produced round seeds
What is the term used to describe the concept that an organism inherits two copies of a gene, one from each parent?
Diploidy
What is the result of the combination of a dominant and a recessive allele in a diploid organism?
The dominant allele determines the organism's appearance
What is the term used to describe the physical location of a gene on a chromosome?
Locus
What is the ratio of purple to white flowers in the F2 generation?
3:1
What is the term used to describe the concept that an organism's appearance is determined by the dominant allele?
Dominance
What is the term used to describe the process of hiding or masking of one trait by another?
Dominance
What is the term used to describe the different versions of a gene that account for variations in inherited characters?
Alleles
Study Notes
Heritable Variations
- Observations of human traits such as eye color (brown, blue, or gray) and hair color (black, brown, or blond) demonstrate the remarkable variety and diversity of human characteristics.
- These traits are heritable, meaning they can be passed down from parents to offspring.
The Blending Hypothesis
- The blending hypothesis was a popular idea in the 1800s that suggested genetic material from parents mixes together like paint colors.
- According to this hypothesis, the genetic material would blend to produce a uniform population over many generations.
- However, this hypothesis fails to explain the following:
- Why we don't see a uniform population in freely mating populations.
- How traits can reappear after skipping a generation.
The Particulate Hypothesis (Gene Idea)
- The particulate hypothesis proposes that parents pass on discrete, heritable units called genes.
- These genes retain their separate identities in offspring and are not blended or mixed.
- The collection of genes in an organism is like a deck of cards, which can be shuffled and passed along to the next generation in undiluted form.
Modern Genetics
- The study of modern genetics originated in an abbey garden, where Gregor Mendel conducted experiments on pea plants.
- Mendel developed a theory of inheritance based on the particulate mechanism, which laid the foundation for modern genetics.
Mendel's Contributions to Genetics
- Gregor Mendel, an Austrian monk, discovered the basic principles of heredity by breeding garden peas in carefully planned experiments.
- Mendel's experiments were key to understanding the principles of inheritance.
Mendel's Approach
- Mendel's approach was experimental and quantitative, using large sample sizes and accurate records.
- He chose to track only those characters that occurred in two distinct, alternative forms, such as purple or white flower color.
- Mendel started his experiments with varieties that were true-breeding, meaning they produced only the same variety as the parent plant.
Hybridization
- Mendel cross-pollinated two contrasting, true-breeding pea varieties, producing hybrid offspring (F1 generation).
- He then allowed these F1 hybrids to self-pollinate, producing an F2 generation.
The Law of Segregation
- Mendel observed that the F1 hybrids had a combination of traits from the parent plants, but the F2 generation showed a 3:1 ratio of dominant to recessive traits.
- Mendel reasoned that the heritable factor for the recessive trait did not disappear in the F1 plants, but was hidden by the dominant trait.
- The law of segregation states that the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes.
Mendel's Model
- Mendel developed a model to explain the 3:1 inheritance pattern he observed:
- Alternative versions of genes (alleles) account for variations in inherited characters.
- An organism inherits two copies of a gene (two alleles) from its parents.
- If the two alleles differ, one is dominant and the other is recessive.
- The two alleles segregate during gamete formation and end up in different gametes.
Key Concepts
- Homozygote: an organism with two identical alleles for a gene.
- Heterozygote: an organism with two different alleles for a gene.
- Phenotype: an organism's appearance or observable traits.
- Genotype: an organism's genetic makeup.
- Testcross: breeding an organism of unknown genotype with a recessive homozygote to determine its genotype.
The Law of Independent Assortment
- Mendel's experiments with two characters (seed color and seed shape) showed that the alleles for one gene segregate into gametes independently of the alleles of another gene.
- The law of independent assortment states that two or more genes assort independently during gamete formation, resulting in a 9:3:3:1 phenotypic ratio in the F2 generation.
Mendel's Contributions to Genetics
- Gregor Mendel, an Austrian monk, discovered the basic principles of heredity by breeding garden peas in carefully planned experiments.
- Mendel's experiments were key to understanding the principles of inheritance.
Mendel's Approach
- Mendel's approach was experimental and quantitative, using large sample sizes and accurate records.
- He chose to track only those characters that occurred in two distinct, alternative forms, such as purple or white flower color.
- Mendel started his experiments with varieties that were true-breeding, meaning they produced only the same variety as the parent plant.
Hybridization
- Mendel cross-pollinated two contrasting, true-breeding pea varieties, producing hybrid offspring (F1 generation).
- He then allowed these F1 hybrids to self-pollinate, producing an F2 generation.
The Law of Segregation
- Mendel observed that the F1 hybrids had a combination of traits from the parent plants, but the F2 generation showed a 3:1 ratio of dominant to recessive traits.
- Mendel reasoned that the heritable factor for the recessive trait did not disappear in the F1 plants, but was hidden by the dominant trait.
- The law of segregation states that the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes.
Mendel's Model
- Mendel developed a model to explain the 3:1 inheritance pattern he observed:
- Alternative versions of genes (alleles) account for variations in inherited characters.
- An organism inherits two copies of a gene (two alleles) from its parents.
- If the two alleles differ, one is dominant and the other is recessive.
- The two alleles segregate during gamete formation and end up in different gametes.
Key Concepts
- Homozygote: an organism with two identical alleles for a gene.
- Heterozygote: an organism with two different alleles for a gene.
- Phenotype: an organism's appearance or observable traits.
- Genotype: an organism's genetic makeup.
- Testcross: breeding an organism of unknown genotype with a recessive homozygote to determine its genotype.
The Law of Independent Assortment
- Mendel's experiments with two characters (seed color and seed shape) showed that the alleles for one gene segregate into gametes independently of the alleles of another gene.
- The law of independent assortment states that two or more genes assort independently during gamete formation, resulting in a 9:3:3:1 phenotypic ratio in the F2 generation.
Learn about heritable variations in human traits and the blending hypothesis, a 19th-century idea on genetic inheritance. Understand how genetic material is passed down from parents to offspring.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
