go to section: analyzing inheritance offspring resemble their parents. offspring inherit genes for...

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Analyzing Inheritance

Offspring resemble their parents. Offspring inherit genes for characteristics from their parents. To learn about inheritance, scientists have experimented with breeding various plants and animals.

In each experiment shown in the table on the next slide, two pea plants with different characteristics were bred. Then, the offspring produced were bred to produce a second generation of offspring. Consider the data and answer the questions that follow.

Section 11-1

Interest Grabber

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1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?

2. How do the characteristics of the second generation compare to the characteristics of the first generation?

Section 11-1

Interest Grabber continued

Parents

Long stems short stems

Red flowers white flowers

Green pods yellow pods

Round seeds wrinkled seeds

Yellow seeds green seeds

First Generation

All long

All red

All green

All round

All yellow

Second Generation

787 long: 277 short

705 red: 224 white

428 green: 152 yellow

5474 round: 1850 wrinkled

6022 yellow: 2001 green

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11–1 The Work of Gregor MendelA. Gregor Mendel’s Peas

B. Genes and Dominance

C. Segregation

1. The F1 Cross

2. Explaining the F1 Cross

Section 11-1

Section Outline

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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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Tossing Coins

If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin

ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.

Section 11-2

Interest Grabber

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1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?

2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?

3. If you compiled the results for the whole class, what results would you expect?

4. How do the expected results differ from the observed results?

Section 11-2

Interest Grabber continued

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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 Cross

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Section 11-2

Tt X Tt Cross

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Height in Humans

Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the ecessive one. What about people? Are the factors that determine height more complicated in humans?

Section 11-3

Interest Grabber

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1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches.

2. What can you observe about the heights of the ten people?

3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.

Section 11-3

Interest Grabber continued

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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 are dominant,

and some alleles are 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 11-3

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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How Many Chromosomes?

Normal human body cells each contain 46 chromosomes. The cell division process that body cells undergo is called mitosis and produces daughter cells that are virtually identical to the parent cell. Working with a partner, discuss and answer the questions that follow.

Section 11-4

Interest Grabber

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1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?

2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?

3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?

Section 11-4

Interest Grabber continued

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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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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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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

Videos

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Meiosis Overview

Animal Cell Meiosis, Part 1

Animal Cell Meiosis, Part 2

Segregation of Chromosomes

Crossing Over

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

The latest discoveries in genetics

Interactive test

Articles on genetics

For links on Punnett squares, go to www.SciLinks.org and enter the Web Code as follows: cbn-4112.

For links on Mendelian genetics, go to www.SciLinks.org and enter the Web Code as follows: cbn-4113.

For links on meiosis, go to www.SciLinks.org and enter the Web Code as follows: cbn-4114.

Go Online

Interest Grabber Answers

1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?

All offspring had the same characteristic, which was like one of the parents’. The other characteristic seemed to have disappeared.

2. How do the characteristics of the second generation compare to the characteristics of the first generation?

Both characteristics appeared in this generation. The characteristic that had “disappeared” in the first generation did not appear as often as the other characteristic. (It appears about 25 percent of the time.)

Interest Grabber Answers

1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?

Results will vary, but should be close to 5 heads and 5 tails.

2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?

The results for 20 tosses may be closer to the predicted 10 heads and 10 tails.

3. If you compiled the results for the whole class, what results would you expect?

The results for the entire class should be even closer to the number predicted by the rules of probability.

4. How do the expected results differ from the observed results?

The observed results are usually slightly different from the expected results.

Interest Grabber Answers

1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches.

Check students’ answers to make sure they are realistic.

2. What can you observe about the heights of the ten people?

Students should notice that there is a range of heights in humans.

3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.

No, height does not seem to be controlled by two alleles, as it is in pea plants. Height in humans can vary greatly and is not just found in tall and short phenotypes.

Interest Grabber Answers

1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?

46 chromosomes

2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?

46 + 46 = 92; a developing embryo would not survive if it contained 92 chromosomes.

3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?

Sperm and egg should each have 23 chromosomes.

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.

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