Genetics Chapter 12: Mendel's Experiments

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Questions and Answers

What does the principle of independent assortment state?

All offspring genes for a trait come from one parent

All traits are inherited independently of each other

Genes for different traits can segregate independently during the formation of gametes (correct)

Genes always segregate together during gamete formation

Which combination represents a genotype example of heterozygous?

Gg (correct)

In a Punnett square, where are the alleles of the first parent written?

Along the diagonal

Along the top edge (correct)

Along the right edge

Along the bottom edge

In a two-factor cross F2 generation, what is the expected phenotypic ratio?

9:3:3:1 Signup and view all the answers

What is a phenotype?

A physical trait inherited from parents Signup and view all the answers

According to Mendel's principles, what determines biological inheritance?

Factors that are passed from one generation to the next Signup and view all the answers

In diploid cells, what does each chromosome from the male parent have?

A corresponding chromosome from the female parent Signup and view all the answers

What is the process called where the number of chromosomes per cell is cut in half through a separation of homologous chromosomes in diploid cells?

Meiosis Signup and view all the answers

During which phase of meiosis does a tetrad form and undergo processes called crossing-over?

Prophase I Signup and view all the answers

Which phase directly follows Metaphase I in meiosis?

Anaphase I Signup and view all the answers

What forms around each cluster of chromosomes during Telophase I of meiosis?

A nuclear membrane Signup and view all the answers

What is the defining characteristic of incomplete dominance in allele expression?

Heterozygotes phenotype lies somewhere between the two homozygous phenotypes. Signup and view all the answers

How is codominance different from the traditional dominant-recessive relationship?

Phenotypes produced by both alleles are clearly expressed in heterozygotes. Signup and view all the answers

In the context of codominance, what is an example of a human trait that demonstrates this phenomenon?

Blood type AB showing traits of both A and B alleles. Signup and view all the answers

Which statement accurately describes the phenotype of a heterozygote in incomplete dominance?

It will have a mixed phenotype that is a blend of the two homozygous phenotypes. Signup and view all the answers

Which scenario is an example of codominance in genetics?

A flower that shows a mix of red and white spots due to equal expression of red and white alleles. Signup and view all the answers

Which cell division process results in daughter cells that each receive a complete diploid set of chromosomes?

Mitosis Signup and view all the answers

What term appropriately describes the genetic material received by daughter cells in mitosis?

Diploid Signup and view all the answers

During which phase of cell division is a complete diploid set of chromosomes distributed to each daughter cell?

Cytokinesis of Mitosis Signup and view all the answers

Which process does NOT result in the formation of genetically identical daughter cells?

Meiosis I Signup and view all the answers

What feature distinguishes the cell division process that forms diploid daughter cells?

Equal distribution of genetic material resulting in identical cells Signup and view all the answers

What is the scientific study of biological inheritance called?

Genetics Signup and view all the answers

Why did Gregor Mendel choose garden peas for his experiments?

They are easy to grow and produce hundreds of offspring. Signup and view all the answers

What is fertilization in the context of sexual reproduction in plants?

When male and female reproductive cells join to produce a new cell. Signup and view all the answers

What are hybrids in the context of Mendel's experiments?

Offspring resulting from cross-fertilization with different contrasting characteristics Signup and view all the answers

What is the term used to describe the original pair of plants in Mendel's genetic crosses?

Parental generation Signup and view all the answers

What happened to the traits of the other parent in the F1 hybrid plants studied by Mendel?

They seemed to have disappeared. Signup and view all the answers

Which statement best describes one of Mendel's conclusions from his experiments?

An individual's characteristics are determined by factors passed from one parental generation to the next. Signup and view all the answers

What was one specific characteristic Mendel focused on in his experiments?

Plant height Signup and view all the answers

Which of the following best explains Mendel's principle of dominance?

Some alleles are dominant and others are recessive Signup and view all the answers

What was the purpose of Mendel allowing F1 hybrids to self-pollinate?

To see if recessive alleles were still present Signup and view all the answers

During the formation of gametes, what happens to the alleles for each gene?

Alleles for each gene segregate so each gamete carries only one allele Signup and view all the answers

What was Mendel's observation in the F1 cross regarding the yellow and green pod alleles?

The alleles separated, indicating the process of segregation Signup and view all the answers

What is the probability of an F1 gamete carrying a yellow pod allele?

50% Signup and view all the answers

According to Mendel's principles, what are alleles?

Different forms of a single gene Signup and view all the answers

How did Mendel explain the reappearance of recessive traits in the F2 generation?

He proposed that recessive alleles were only temporarily hidden in the F1 generation Signup and view all the answers

How does probability apply to genetic crosses according to Mendel's principles?

Probability shows the likelihood of particular traits appearing in the offspring Signup and view all the answers

Study Notes

The Work of Gregor Mendel

Mendel conducted experiments on garden peas to study biological inheritance, now known as genetics.
He chose peas as "model organisms" due to their ease of growth and high offspring production.
In sexual reproduction, male and female reproductive cells join to form a new cell, with each parent contributing half of the genetic material.

Traits and Genetic Crosses

Mendel studied seven sets of pea plants with contrasting characteristics, self-crossing them to produce hybrids.
The offspring exhibited only one of the parental characteristics, with the other trait seemingly "disappearing".
This led to two conclusions:
An individual's characteristics are determined by factors passed from one parental generation to the next.
These factors are the physical differences in appearance or forms of each trait.

Genes and Alleles

The different forms of a single gene are called alleles.
Mendel's principle of dominance states that some alleles are dominant, while others are recessive.
When an organism has both a dominant and a recessive allele, the dominant characteristic is exhibited.

Segregation

Mendel crossed F1 hybrids to produce a F2 generation, finding that recessive alleles did not disappear, but segregated during gamete formation.
Alleles for each gene segregate from each other during gamete formation, with each gamete carrying only one allele for each gene.

Probability and Heredity

Probability is used to explain the results of genetic crosses.
Each F1 plant produces two kinds of gametes, with a 1/2 chance of carrying a specific allele.
Punnett squares are used to predict the probability of certain genotypes and phenotypes.

Genotype and Phenotype

Phenotype refers to the physical trait, while genotype refers to the genetic makeup.
Genotype and phenotype can differ, as plants with different genotypes can have the same phenotype.

Independent Assortment

Mendel's principle of independent assortment states that genes for different traits can segregate independently during gamete formation.
This is demonstrated by the 9:3:3:1 ratio of phenotypes in a two-factor cross.

Other Patterns of Inheritance

Incomplete dominance occurs when alleles are neither completely dominant nor recessive.
Codominance occurs when both alleles are expressed in the phenotype.
Chromosomes are the genetic material that fit the description of independent assortment.

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Description

Learn about the scientific study of biological inheritance, specifically Gregor Mendel's experiments with garden peas and the role of fertilization in genetics.