Mendel's Genetics Experiments

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Questions and Answers

What was the significance of Gregor Mendel's experiments with pea plants?

They established principles of inheritance. (correct)

They introduced genetics as a scientific discipline.

They identified chromosomes as carriers of genes.

They explained the structure of DNA.

What is the relationship between genotype and phenotype?

Phenotype can exist independently of genotype.

Phenotype has no correlation to genotype.

Gene expression results in a phenotype based on a genotype. (correct)

Genotype determines the phenotype without exceptions.

What type of cells contain paired homologous chromosomes?

Diploid cells (correct)

Triploid cells

Monoploid cells

Haploid cells

What happened to Mendel's work after it was published?

It was largely ignored for approximately 35 years. Signup and view all the answers

How was Gregor Mendel's research environment best described?

A monastery garden Signup and view all the answers

What is the genotype of all offspring resulting from the cross PP x pp?

Pp Signup and view all the answers

What phenotype do all offspring from the cross PP x pp exhibit?

Purple Signup and view all the answers

From the Punnett square of Pp x Pp, what is the expected ratio of phenotypes among the offspring?

1:2:1 Signup and view all the answers

What proportion of offspring from the cross Pp x Pp are expected to be homozygous recessive?

1/4 Signup and view all the answers

In the Pp x Pp cross, how many offspring are expected to be heterozygotes?

2 Signup and view all the answers

What is the expected phenotype ratio of a monohybrid cross between two heterozygous individuals?

3:1 Signup and view all the answers

Which genotype will produce a white flower phenotype?

pp Signup and view all the answers

What can be determined from the frequency of traits in the offspring of a Mendelian cross?

The dominant trait's inheritance pattern Signup and view all the answers

In a monohybrid cross, what does it mean for an allele to be dominant?

It is always expressed in the phenotype Signup and view all the answers

What is the purpose of a Punnett Square in genetic crosses?

To predict the genotypes of the offspring Signup and view all the answers

Which of the following best describes continuous variation?

A range of small differences in a shared trait. Signup and view all the answers

What is the primary difference between diploid and haploid cells?

Diploid cells contain paired chromosomes, while haploid cells do not. Signup and view all the answers

What is a characteristic of a homozygous genotype?

It contains two identical alleles. Signup and view all the answers

Which of the following statements about heterozygous individuals is true?

They can have one dominant and one recessive allele. Signup and view all the answers

Discrete variation is best described as what?

Variation limited to specific categories. Signup and view all the answers

What distinguishes phenotype from genotype in Mendelian genetics?

Phenotype is the observable characteristics, while genotype is the genetic makeup. Signup and view all the answers

What is the expected phenotypic ratio in the F2 generation from a monohybrid cross between two heterozygous organisms (Yy)?

75% yellow and 25% green. Signup and view all the answers

In a test cross where the unknown parent is heterozygous, what ratio of phenotypes would be expected among the offspring?

A 1:1 ratio of dominant to recessive phenotypes. Signup and view all the answers

What does the law of independent assortment state?

Alleles for different traits sort into gametes independently of one another. Signup and view all the answers

Which Punnett Square outcome would indicate that a dominant phenotype is homozygous?

All offspring exhibit the dominant phenotype. Signup and view all the answers

What does the Law of Segregation state about paired genes?

Paired genes segregate equally into gametes. Signup and view all the answers

How does the Law of Independent Assortment contribute to genetic diversity?

It allows for the random segregation of multiple traits. Signup and view all the answers

What genetic principle describes the expression of both alleles in a heterozygote?

Codominance Signup and view all the answers

What role does epistasis play in the inheritance of traits?

It includes interactions between multiple gene products affecting traits. Signup and view all the answers

What is one consequence of having 23 pairs of chromosomes in humans?

There are over 2 million unique combinations of parental chromosomes. Signup and view all the answers

Which example best illustrates incomplete dominance?

Red and white flowers producing pink offspring Signup and view all the answers

Which term best describes a heritable condition that results in a set of symptoms?

Genetic disorder Signup and view all the answers

What does phenotypic plasticity refer to in living organisms?

The capacity to express different traits in response to environmental changes Signup and view all the answers

In human genetic analysis, what is typically illustrated through pedigrees?

Inheritance patterns of specific phenotypes Signup and view all the answers

Which type of genetic disorder is expressed only in homozygotes?

Autosomal recessive Signup and view all the answers

Which condition is an example of autosomal recessive inheritance?

Albinism Signup and view all the answers

What is the primary reason for the persistence of recessive alleles in populations?

Individuals with one recessive allele do not exhibit symptoms. Signup and view all the answers

In X-linked recessive inheritance, who cannot transmit the disorder to their sons?

Males Signup and view all the answers

Which of the following is NOT an X-linked recessive disorder?

Cystic Fibrosis Signup and view all the answers

What advantage do heterozygous genotypes provide in sub-Saharan Africa regarding sickle-cell anemia?

Resistance to malaria Signup and view all the answers

Study Notes

Mendel's Experiments

Gregor Mendel's experiments with pea plants in the mid-1800s established the principles of inheritance
His work, published in 1866, was overlooked for approximately 35 years.

Inheritance in Modern Terms

Gene expression leads to an organism's phenotype based on its genotype
Diploid cells have paired homologous chromosomes, one from each parent.

Forms of Variation

Continuous variation describes a range of small differences in a shared trait like flower color or eye color.
Discrete variation is a binary expression of a trait.

Homozygous and Heterozygous Genotypes

Homozygous individuals have identical alleles for a gene
Heterozygous individuals have two different alleles for a gene

Monohybrid Crosses

Monohybrid crosses involve individuals with different alleles for a single gene
Dominant alleles (P) will always mask recessive alleles (p)
A cross between heterozygous individuals can reveal dominance among alleles

Punnett Squares

A Punnett square is used to calculate the possible genotypes and phenotypes of offspring from a cross
The dominant trait will show up in a 3:1 phenotype ratio in a cross between two heterozygotes
Mendel was able to predict the traits of offspring without understanding the underlying causes because of the patterns he observed

Law of Segregation

Paired genes separate equally into gametes
This ensures offspring have an equal chance of inheriting either factor

Law of Independent Assortment

During meiosis, different genes segregate independently of one another
This produces a huge amount of genetic variation with numerous unique combinations of parental chromosomes.

Phenotype vs. Genotype

The phenotype is the observable characteristic of an organism, like flower color
The genotype is the genetic makeup of an organism which determines the phenotype

Simple Dominance

Simple dominance is observed in traits like human skin color, where multiple genes and alleles are involved.

Epistasis

Epistasis refers to the phenomenon where multiple genes can interact to affect a single trait.

Codominance and Multiple Alleles

Codominance occurs when two alleles are fully expressed in a heterozygote individual
Human blood types are an example of codominance and multiple alleles, with different combinations of A, B, and O alleles producing different blood types.

Incomplete Dominance

Incomplete dominance occurs when one allele is not fully dominant over another
The heterozygote phenotype is a blend of the two homozygous phenotypes; for example, wavy hair is an intermediate phenotype between curly and straight hair.

Phenotypic Plasticity

Phenotypic plasticity is the ability of an organism's phenotype to change in response to environmental conditions
The snowshoe hare's fur color changes seasonally, an example of phenotypic plasticity.

Types of Genetic Variation

A genetic abnormality is an uncommon version of a heritable trait but does not necessarily cause medical problems
A genetic disorder is a heritable condition resulting in a syndrome of medical problems, from mild to severe.

Autosomal Dominant Inheritance

Traits are expressed in both homozygous and heterozygous genotypes, showing up in every generation.
Examples: Huntington's disease, Achondroplasia, Polydactyly

Autosomal Recessive Inheritance

Traits are only expressed in homozygous genotypes, often skipping generations.
Examples: Albinism, Sickle-cell anemia, Tay-Sachs disease, Cystic fibrosis

X-linked Recessive Disorders

Alleles on the X chromosome are inherited differently in males and females
Fathers cannot pass these traits to sons, but daughters can be carriers
Examples: Muscular dystrophy, colorblindness (red-deficient, green-deficient), Hemophilia

Pedigrees

Pedigrees are used in human genetic analysis to illustrate phenotypes in families and determine if traits are associated with dominant or recessive alleles.
Pedigrees can also help track traits across generations, indicating if a trait is located on an autosome or sex chromosome.

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Description

Explore Gregor Mendel's groundbreaking experiments with pea plants and their significance in understanding inheritance. This quiz covers concepts like gene expression, variation forms, and monohybrid crosses that lay the foundation for modern genetics. Test your knowledge on homozygous and heterozygous genotypes!