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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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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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GENETICS

Heredity- Passing characteristics from parent to offspring.

Genetics- The scientific study of heredity.

Gregor MendelAustrian 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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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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P1 Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

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Important Genetics VocabularyTrait- 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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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.

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. 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?

Section 11-2

Interest Grabber continued

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Coin Toss

Expected Results-

Observed Results-

Note: Alleles have a 50/50 chance of being selected.

Section 11-2

Section Outline

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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 11-2

Tt X Tt Cross Monohybrid Cross

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Section 11-2

Tt X Tt Cross

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Pause for Punnett Square Practice

Section 11-3

Interest Grabber

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Punnett Square Practice

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concluded that

which is called the

which is called the

GregorMendel

Law ofDominance

Law ofSegregation

Peaplants

“Factors”(genes)determine

traits

Some alleles are dominant,

and some alleles are recessive

Alleles are separated during gamete formation.

One allele from eachparent.

Section 11-3

Concept Map

experimented with

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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 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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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 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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Section 11-4

Crossing-Over

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

Click the image to play the video segment.

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

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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