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The Father of Genetics – Gregor Johann Mendel (1822-1884)

1863 - 1866 Mendel cultivated and tested some 28 000 pea plants

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Allele – Different form of a gene

Dominant allele - In a heterozygote, the allele that is fully expressed in the phenotype.

Recessive allele - In a heterozygote, the allele that is completely masked in the phenotype.

Phenotype – The outward appearance of a trait

Genotype – The combination of alleles (Letters)

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Mendel’s Experiments

•Used 34 "true-breeding" strains of the common garden pea plant•These strains differed from each other in very pronounced (visible) ways so that there could be no doubt as the results of a given experiment. •Pea plants were perfect for such experiments since their flowers had both male (anthers) and female (pistils) flower parts•The flower petals never open therefore no foreign pollen could enter and back crosses (self fertilization) was easy.

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Flower Parts

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P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

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P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

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P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

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Seed Shape

Flower Position

Seed CoatColor

Seed Color

Pod Color

Plant Height

PodShape

Round

Wrinkled

Round

Yellow

Green

Gray

White

Smooth

Constricted

Green

Yellow

Axial

Terminal

Tall

Short

Yellow Gray Smooth Green Axial Tall

Section 11-1

Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants

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11–2 Probability and Punnett SquaresA. Genetics and Probability

B. Punnett Squares

C. Probability and Segregation

D. Probabilities Predict Averages

Section 11-2

Section Outline

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Section 11-2

Tt X Tt Monohybrid Cross

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Section 11-2

Tt X Tt Cross

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Monohybrid Cross Phenotypes

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Law of Segregation

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11–3 Exploring Mendelian GeneticsA. Independent Assortment

1. The Two-Factor Cross: F1

2. The Two-Factor Cross: F2

B. A Summary of Mendel’s Principles

C. Beyond Dominant and Recessive Alleles

1. Incomplete Dominance

2. Codominance

3. Multiple Alleles

4. Polygenic Traits

D. Applying Mendel’s Principles

E. Genetics and the Environment

Section 11-3

Section Outline

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concluded that

which is called the

which is called

the

GregorMendel

Law ofDominance

Law ofSegregation

Peaplants

“Factors”determine

traits

Some alleles dominant,

& some alleles recessive

Alleles are separated during gamete formation

Section 11-3

Concept Map

experimented with

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Section 11-3

Figure 11-10 Independent Assortment in Peas

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Section 11-2

Dihybrid Cross

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Section 11-3

Figure 11-11 Incomplete Dominance in Four O’Clock Flowers

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Section 11-3

Figure 11-11 Incomplete Dominance in Four O’Clock Flowers

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11–4 MeiosisA. Chromosome Number

B. Phases of Meiosis

1. Meiosis I

2. Meiosis II

C. Gamete Formation

D. Comparing Mitosis and Meiosis

Section 11-4

Section Outline

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Homologous Chromosome

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Section 11-4

Crossing-Over

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Section 11-4

Crossing-Over

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Section 11-4

Crossing-Over

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Meiosis I

Section 11-4

Figure 11-15 Meiosis

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Meiosis I

Section 11-4

Figure 11-15 Meiosis

Meiosis I

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Meiosis I

Section 11-4

Figure 11-15 Meiosis

Meiosis I

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Section 11-4

Figure 11-15 Meiosis

Meiosis I

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Section 11-4

Figure 11-15 Meiosis

Meiosis I

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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Genetic Recombination

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Forever Linked?

Some genes appear to be inherited together, or “linked.” If two genes

are found on the same chromosome, does it mean they are linked forever?

Study the diagram, which shows four genes labeled A–E and a–e, and then answer the questions on the next slide.

Section 11-5

Interest Grabber

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1. In how many places can crossing over result in genes A and b being on the same chromosome?

2. In how many places can crossing over result in genes A and c being on the same chromosome? Genes A and e?

3. How does the distance between two genes on a chromosome affect the chances that crossing over will recombine those genes?

Section 11-5

Interest Grabber continued

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11–5 Linkage and Gene MapsA. Gene Linkage

B. Gene Maps

Section 11-5

Section Outline

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Earth

Country

State

City

People

Cell

Chromosome

Chromosome fragment

Gene

Nucleotide base pairs

Section 11-5

Comparative Scale of a Gene Map

Mapping of Earth’s Features

Mapping of Cells, Chromosomes, and Genes

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Exact location on chromosomes Chromosome 2

Section 11-5

Figure 11-19 Gene Map of the Fruit Fly

Click the image to play the video segment.

Video 1

Meiosis Overview

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Video 2

Animal Cell Meiosis, Part 1

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Video 3

Animal Cell Meiosis, Part 2

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Video 4

Segregation of Chromosomes

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Video 5

Crossing Over

Interest Grabber Answers

1. In how many places can crossing over result in genes A and b being on the same chromosome?

One (between A and B)

2. In how many places can crossing over result in genes A and c being on the same chromosome? Genes A and e?

Two (between A and B and A and C); Four (between A and B, A and C, A and D, and A and E)

3. How does the distance between two genes on a chromosome affect the chances that crossing over will recombine those genes?

The farther apart the genes are, the more likely they are to be recombined through crossing over.