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Interest Grabber
Section 11-1
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.
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Section:
Interest Grabber continued
Section 11-1
Parents
First Generation
Second Generation
Long stems  short stems
All long
787 long: 277 short
Red flowers  white flowers
All red
705 red: 224 white
Green pods  yellow pods
All green
428 green: 152 yellow
Round seeds  wrinkled seeds All round
5474 round: 1850 wrinkled
Yellow seeds  green seeds
6022 yellow: 2001 green
All yellow
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?
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Section:
Section Outline
Section 11-1
11–1
The Work of Gregor Mendel
A. Gregor Mendel’s Peas
B. Genes and Dominance
C. Segregation
1. The F1 Cross
2. Explaining the F1 Cross
Go to
Section:
Principles of Dominance
Section 11-1
P Generation
Tall
Go to
Section:
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Principles of Dominance
Section 11-1
P Generation
Tall
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Section:
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Principles of Dominance
Section 11-1
P Generation
Tall
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Section:
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Figure 11-3 Mendel’s Seven F1 Crosses
on Pea Plants
Section 11-1
Seed Coat
Color
Pod
Shape
Pod
Color
Smooth
Green
Seed
Shape
Seed
Color
Round
Yellow
Gray
Wrinkled
Green
White
Constricted
Round
Yellow
Gray
Smooth
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Section:
Flower
Position
Plant
Height
Axial
Tall
Yellow
Terminal
Short
Green
Axial
Tall
Interest Grabber
Section 11-2
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.
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Section:
Interest Grabber continued
Section 11-2
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?
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Section:
Section Outline
Section 11-2
11–2
Probability and Punnett Squares
A.
B.
C.
D.
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Section:
Genetics and Probability
Punnett Squares
Probability and Segregation
Probabilities Predict Averages
Tt X Tt Cross
Section 11-2
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Section:
Tt X Tt Cross
Section 11-2
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Section:
Interest Grabber
Section 11-3
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?
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Section:
Interest Grabber continued
Section 11-3
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.
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Section:
Section Outline
Section 11-3
11–3
Exploring Mendelian Genetics
A. 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
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Section:
Concept Map
Section 11-3
Gregor
Mendel
concluded
that
experimented
with
Pea
plants
“Factors”
determine
traits
Some alleles
are dominant,
and some alleles
are recessive
which is
called the
Law of
Dominance
Go to
Section:
Alleles are
separated during
gamete formation
which is
called the
Law of
Segregation
Figure 11-10 Independent Assortment in Peas
Section 11-3
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Section:
Figure 11-11 Incomplete Dominance in
Four O’Clock Flowers
Section 11-3
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Section:
Figure 11-11 Incomplete Dominance in
Four O’Clock Flowers
Section 11-3
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Section:
Interest Grabber
Section 11-4
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.
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Section:
Interest Grabber continued
Section 11-4
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?
Go to
Section:
Section Outline
Section 11-4
11–4
Meiosis
A. Chromosome Number
B. Phases of Meiosis
1. Meiosis I
2. Meiosis II
C. Gamete Formation
D. Comparing Mitosis and Meiosis
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Section:
Crossing-Over
Section 11-4
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Section:
Crossing-Over
Section 11-4
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Section:
Crossing-Over
Section 11-4
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Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Go to
Section:
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Interest Grabber
Section 11-5
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.
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Section:
Interest Grabber continued
Section 11-5
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?
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Section:
Section Outline
Section 11-5
11–5
Linkage and Gene Maps
A. Gene Linkage
B. Gene Maps
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Section:
Comparative Scale of a Gene Map
Section 11-5
Mapping of Earth’s
Features
Mapping of Cells,
Chromosomes, and Genes
Cell
Earth
Country
Chromosome
State
Chromosome
fragment
City
People
Go to
Section:
Gene
Nucleotide
base pairs
Figure 11-19 Gene Map of the Fruit Fly
Section 11-5
Exact location on chromosomes
Go to
Section:
Chromosome 2
Videos
Click a hyperlink to choose a video.
Meiosis Overview
Animal Cell Meiosis, Part 1
Animal Cell Meiosis, Part 2
Segregation of Chromosomes
Crossing Over
Video 1
Meiosis Overview
Click the image to play the video segment.
Video 2
Animal Cell Meiosis, Part 1
Click the image to play the video segment.
Video 3
Animal Cell Meiosis, Part 2
Click the image to play the video segment.
Video 4
Segregation of Chromosomes
Click the image to play the video segment.
Video 5
Crossing Over
Click the image to play the video segment.
Go Online
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.
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.
This slide is intentionally blank.