Download Section 11-2

Answer the following questions to the best of your
ability.
•What is genetics?
• How do sexually reproducing organisms obtain
different traits?
• Who is Gregor Mendel?
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Section:
Important!!!
Knowing your vocabulary is especially
important in genetics. The better you
know the vocabulary in this unit, the
easier it will be.
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Section:
GENETICS
Heredity- Passing characteristics from parent to offspring.
Genetics- The scientific study of heredity.
Gregor Mendel
Austrian monk known as the father of genetics. Studied
pea plants and changed biology forever. Usually pea plants
self pollinate (pollinate themselves). He found that when he
cross pollinated (crossing sex cells of different plants)
plants with different characteristics he got some interesting
results.
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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:
Principles of Dominance
Section 11-1
P1 Generation
Tall
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Section:
Short
F1 Generation
Tall
Tall
F2 Generation
Tall
Tall
Tall
Short
Important Genetics Vocabulary
Trait- Specific characteristics such as seed color or plant height.
Dominant-masks a recessive trait
Recessive-masked by dominant trait
Genes- Chemical “factors” that determine traits.
Alleles- Different forms of a gene. Capital letter represents a dominant
allele. Lowercase letter represents recessive allele.
Trait- Height (you can see it)
Gene- Tt (you cannot see it)
Alleles- T-dominant for tallness; t-recessive for shortness (make up genes)
Alleles-> Gene-> Trait
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More important vocabulary…
Purebred- Offspring from two parents with like traits
Hybrid- Offspring of crosses between two parents with different traits.
Gametes- Sex cells; reproductive cells
e.g. Humans- male sperm; female egg
Flowers- male pollen; female egg
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Section:
Interest Grabber
Section 11-2
Probability- the likelihood that a particular event will occur.
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.
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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. If you compiled the results for the whole class, what results would you
expect?
3. How do the expected results differ from the observed results?
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Section:
Section Outline
Section 11-2
Coin Toss
Expected Results-
Observed Results-
Note: Alleles have a 50/50 chance of being selected.
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Section:
Punnett Squares
Punnett Square- A diagram used to determine gene combinations from a
genetic cross.
Homozygous- same type of alleles (TT; tt)
Heterozygous- different type of alleles (Tt)
Phenotype- physical characteristics (tall, short, round, wrinkled)
Genotype- genetic makeup ( TT, Tt, tt, RR, Rr, rr)
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Section:
Tt X Tt Cross
Section 11-2
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Section:
Monohybrid Cross
Tt X Tt Cross
Section 11-2
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Section:
Interest Grabber
Section 11-3
Pause for Punnett Square Practice
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Section:
Punnett Square Practice
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Section:
Concept Map
Section 11-3
Gregor
Mendel
concluded
that
experimented
with
Pea
plants
“Factors”(genes)
determine
traits
Some alleles
are dominant,
and some alleles
are recessive
which is
called the
Law of
Dominance
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Alleles are
separated during
gamete formation.
One allele from each
parent.
which is
called the
Law of
Segregation
New vocabulary words…
Incomplete Dominance-when neither trait is completely dominant
over the other; e.g. white flowers crossed with red flowers may
produce pink flowers
Codominance- both alleles contribute to the phenotype; both
alleles are dominant; e.g. speckled looking chickens have black
and white feathers which are both dominant
Multiple alleles- when genes have more than one allele; e.g fur
color in rabbits (four different alleles) or blood type in humans
Polygenic traits- traits determined by more than one gene; skin
color in humans
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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:
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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Mitosis vs. Meiosis
Mitosis-● dealing with somatic cells like liver cells, skin
cells, and hair cells.
● cell splits once
● end up with 2 diploid daughter cells
Meiosis- ● dealing with gametes (reproductive cells)
● 2 divisions of cells
● end up with 4 haploid daughter cells
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Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
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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.
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Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
Crossing-Over
Section 11-4
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Section:
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.
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