Module 3:1 Lesson

Module 3 Lesson 1
Inheritance

Kokanee Salmon Video

​Kokanee salmon return to the same streams in which they were born to mate. Record your ideas for why you think this happens. Discuss your ideas with three different partners. Revise or update your ideas, if necessary, after the discussions with your classmates.

Poll

Alice and her friends looked at a bunch of ladybugs. they noticed the lady bugs had different numbers of spots. They each had different ideas about why the numbers of spots were different. Read what they said on Page 5. Who do you agree with the most?

• Fred

• Andrea

• Karen

• Isaac

• Troy

​Inheritance

Why do some offspring look like their parents, while others do not?

pg 7

Match

Which kittens do you think belong to the Parents?

A and E

B and C

C and E

A and D

A and B

• A and E

• B and C

• C and E

• A and D

• A and B

​Claim Evidence Reasoning pg 8

Did you see how some of the kittens looked like their parents, but some did not? Use your observations about the phenomenon to make a claim about why offspring sometimes look like their parents.

​Your characteristics are what make you unique. they could be things like hair color or height. These characteristics are called traits. How a trait appears or is expressed, is the trait's PHENOTYPE. Traits such as eye color have many different types, but some traits have only two types.

What do you think determines the type of traits you have?

​INVESTIGATION

Poll

Which earlobe trait do you have?

(ask your neighbor)

• Unattached

• Attached

Poll

What thumb trait do you have?

• Straight

• Curved

Poll

What interlacing finger trait do you have?

• Left thumb over right thumb

• Right thumb over left thumb

​You have just observed a variety of traits within your classroom. These traits were passed to your classmates from their parents. Heredity, the passing of traits from parents to offspring, is complex. For example, you might have strait thumbs, but both of your parents have curved thumbs.

You may have noticed that the kittens at the beginning of the lesson looked similar to their parents. How did the traits of the parents pass to the offspring? More than 150 years ago, Gregor Mendel, an Austrian monk, performed experiments that helped answer this question. Because of his research, Mendel is known as the father of genetics- the study of how traits are passed from parents to offspring.

Mendel performed controlled breeding experiments with pea plants. He began with plants that were true-breeding experiments with pea plants. When a ture-breeding plant pollinates itself, it always produces offspring with traits that match the parent. For example when a true-breeding pea plant with wrinkled seeds self pollinates, it produces only plants with wrinkled seeds.

​Why do offspring look like their parents?

Observe some of Mendel's findings from cross-pollinating (one plant pollinates another) true-breeding plants below. What do you think Mendel discovered when he crossed true-Breeding plants with purple flowers and true-breeding plants with white flowers?

​Why do offspring look like their parents?

​Purple (true-breeding X White (true-breeding)

Observe some of Mendel's findings from cross-pollinating (one plant pollinates another) true-breeding plants below. What do you think Mendel discovered when he crossed true-Breeding plants with purple flowers and true-breeding plants with white flowers?

​Why do offspring look like their parents?

​Purple (true-breeding X White (true-breeding)

First-Generation Crosses
A cross between two true-breeding plants with purple flowers produced plants with only purple flowers. A cross between two true breeding plants with white flowers produced plants with only white flowers. But something unexpected happened when Mendel crossed true-breeding plants with purple flowers ant true-breeding plants with white flowers- All the offspring had purple flowers.
Why didn't the cross produce offspring with light purple flowers- a combination of the white and purple flower colors? Mendel carried out more experiments with pea plants to answer this question.

Second-Generation (Hybrid) Crosses
The first generation purple-flowering plants are called hybrid plants. This means they come from true-breeding parent plans with different forms of the same trait. Mendel wondered what would happen if he crossed-pollinated two purple-flowering hybrid plants. Take a look at his second-generation cross results on the next slide.

​Why do offspring look like their parents?

​Second-Generation (Hybrid) Crosses

​As you observe, some of the offspring had white flowers, even though both parents had purple flowers. The results were similar each time Mendel cross-pollinated two purple-flowering hybrid plants. The trait that had disappeared in the first generation always reappeared in the second generation.
3-D thinking:
What patterns do you notice in the results of Mendel's second-generation cross between hybrid plants with purple Flowers? Explain how the results may have occurred.

Investigation: Look Both Ways Before Crossing the Seed.

​Mendel counted and recorded the traits of offspring from many experiments in which he cross-pollinated hybrid plants. Data from these experiments are shown here.

1. Calculate the relationship of purple to white flowers, yellow to green seeds, round to wrinkled seeds, and smooth to bumpy pods by dividing the higher number by the lower number. Record the answer on the table.

2. What pattern do you notice in Mendel's data?

​A Similar Relationship
From the data of crosses between hybrid plants with purple flowers, Mendel found that the relationship of purple flowers to white flowers was about 3 to 1. This means that purple-flowering pea plants grew from this cross three times more often than White-flowering pea plants grew from the cross. He calculated similar relationships for all traits he tested.

Dominate and Recessive Traits
Recall that Mendel cross-pollinated a true-breeding plant with purple flowers and another with white flowers, the hybrid offspring had only purple flowers. Mendel hypothesized that the hybrid offspring had one genetic factor for purple flowers and one genetic factor for white flowers.
Mendel also hypothesized that the purple factor is the only factor seen or expressed because it blocks the white factor. A genetic factor that blocks another genetic factor is called a dominant trait. A genetic factor that is blocked by the presence of a dominate factor is called a recessive trait.

Collect Evidence

​What did Mendel's experiments show about how the traits of offspring, such as those of the kittens, are inherited? Record your evidence (A) in the chart at the beginning of the lesson

​3-D Thinking

​Now that you have learned about dominant and recessive Traits, take a look back at the table on page 13. Construct an explanation for which seed color is the dominant trait.

​What controls traits?

​ When other scientists studied the parts of a cell and combined Mendel's work with their work, Mendel's factors were more clearly understood. Scientists discovered that inside each cell is a nucleus that contains threadlike structures called chromosomes. Over time, scientists learned that chromosomes contain genetic information that controls traits. We now know that Mendel's "factors" are part of chromosomes and that each cell in offspring contains chromosomes from both parents. These chromosomes exist as pairs - one from each parent.
Scientist have discovered that each chromosome can have information ab out hundreds of even thousands of traits.

• A gene is a section on a chromosome that has genetic information for one trait. The genes on each chromosome can be the same or different, such as purple or white for pea flower color.

• The different forms of a gene are called alleles

• The two alleles that control the phenotype of a trait are called the trait's genotype.

​ Scientists use symbols to represent the alleles in a genotype, as shown in the table below. In genetics, uppercase letters represent dominant alleles and lowercase letters represent recessive alleles. the table shows the possible genotypes for both round and wrinkled seeds phenotypes.
A round seed can have two genotypes- RR and Rr. Both genotypes have a round phenotype. A wrinkled seed can only have one phenotype- rr.

​*A round seed can have have two alleles of a gene are the same, it is homozygous.

*Both RR and rr are homozygous genotypes.

*If the two alleles of a gene are different, its genotype is heterozygous.

*Rr is a heterozygous genotype.

Lab Beetle Genes

​You have learned that two alleles make up a trait's genotype. If you know that beetle traits are either dominant or recessive, how can you use this information to model the genotype of a beetle?

Materials
Trait badges (3)
Colored Pencils

Procedure
1. Select one trait card from each of the three beetle trait bags. Record the trait you selected in the "individuals with trait" column in the table below.

2. Draw a picture of your beetle based on the traits you selected.

Poll

Which wing trait did your beetle have?

• Long Wings

• Short Wings

Poll

Which color trait did your beetle have?

• Green Body

• Red Body

Poll

What spot trait did your beetle have?

• Round Spots

• No Spots

​3. Combine your data with the rest of the class record the total number of individuals with each trait.

Analyze and Conclude

​4. Describe any pattern you find in the data table.

​5. Determine which trait is dominant and which is recessive. Record you responses in the table. Explain you reasoning.

Analyze and Conclude

​6. Determine the possible genotype(s) for each phenotype. Record your
responses in the table. Explain you reasoning.

​7. Decide whether you could have correctly determined your beetle's genotype without data from other beetles. Explain your reasoning.

​Collect Evidence: What factors control traits, such as those of the kittens at the beginning of the lesson? Record your evidence (B) in the chart at the beginning of the lesson.

​How can you predict what offspring will look like?

​Have you ever flipped a coin and guessed heads or tails? Because a coin has two sides, there are only two possible outcomes - heads or tails. You have a 50 percent chance of getting heads and 50 percent chance of getting tails. The ratio comparing 50 to 50 can be written as 50 to 50 OR 50:50, or SIMPLIFIED 1 : 1.

Math Connection A Ratio is a comparison of two numbers or quantities by division.
For example, the ratio comparing 6,022 yellow seeds to 2,001 green seeds can be
written as follows:

To simplify the ratio, divide the first number by the second number.

Given a 3 : 1 ratio, you can expect that an offspring from heterozygous parents has a 3 : 1 parents has a 3 : 1 chance of having yellow seeds. But you cannot expect that a group of four seeds will have three yellow seeds and one green seed. This is because one offspring does not affect the phenotype of another offspring. In a similar way, the outcome of one coin toss does not affect the outcome of other coin tosses.

3-D Thinking

​A cross between two heterozygous pea plants with yellow seeds produced 1,719 yellow seeds and 573 green seeds. What is the ratio of yellow to green seeds? Construct an explanation about what the results show regarding inheritance.

Punnett Squares

​If the genotypes of the parents are known, then the different genotypes and phenotypes of the offspring can be predicted. A Punnett square is a model used to predict possible genotypes and phenotypes of the offspring.
Investigation: Punnett Predictions

​Suppose that you are trying to predict to outcome of a cross between two hybrid plants with yellow pea seeds (genotypes Yy). Recall that yellow seeds are dominant, while green seeds are recessive. To determine the phenotypes of the offspring, follow the prompts and fill in the figure to the right.

1. Split the alleles from the male genotypes, Yy, and place on letter on each column.

2. Split the alleles from the female genotype, Yy, and place one letter on each row.

3. Copy the female alleles across each row. Copy the male alleles down each column. Always list the dominant traits first. The arrows show how to fill in the first square.

4. Add in which genotype will display yellow seeds and which will display green seeds.

​So how did you do? You completed Punnett square should look like this:
Geneticists, or scientists who study genetics, use Punnett Squares to explain how traits are inherited from one generation to the next. Now that you know how to fill in a Punnett square, use the punnett square below to predict the offspring of two fruit flies with different genotypes.

​Investigation
1. Use the Punnett Squares below to complete a cross between a female fruit fly with straight wings (cc) and a male fruit fly with curly wings (CC).

​2. According to your punnett square, which genotypes are possible in the offspring?

​3. If you switch the locations of the parent genotypes around the Punnett square, does it affect the potential genotypes of their offspring? Explain.

​4. Based on the information in your punnett square, what is the ratio of offspring that will have curly wings to straight wings?

​3-D Thinking

​​Design and complete a punnett square to model a cross between two fruit flies that are heterozygous for curly wings (Cc). What is the phenotype ratio of the offspring? Explain how you are able to predict the phenotype ratio of the offspring? Explain how you are able to predict the phenotype ratio based on a cause and effect relationship.

How can you model a family's phenotypes?

​Another model that can show inherited traits is a pedigree. A pedigree shows phenotypes of genetically related family members. It can also help determine genotypes. In the pedigree below, three offspring have a trait- attached earlobes- that the parents do not have. if these offsprings received one allele for this trait from each parent, but neither parent displays the trait, the offspring must have received two recessive alleles.

3-D Thinking

​If the genotype of the offspring with attached lobes is uu, what is the genotype of the parents? Explain your answer.

​Collect Evidence

​ How can inheritance of traits in offspring, such as kittens, be modeled? Record your evidence (C) in the chart and the beginning of the lesson on page 8.

Summary Review

​1. Model a pedigree chart that reflects the following information: Two parents have five children. Both of the parents have curly hair. Two boys and one girl have curly hair; the other two, one boy and one girl, have straight hair. Before you draw your chart choose a color for straight and curly hair, and indicate in the table. After you draw your chart, determine which trait is dominant and label the proper columns in the table.

Multiple Choice

Which is the best explanation that shows the sequence of inheritance that led to Susana having a brother that has the same hairline and eye shape as her great-uncle?

• A

• B

• C

• D

A, B, and D are incorrect because traits must be passed to the grandmother's and mother's generation to reappear in the brother.

​Explanation

Multiple Choice

When Mendel crossed a true-breeding (purebred) plant with purple flowers and true-breeding (purebred) plant with white flowers, ALL offspring had purple flowers. The best explanation for this data is that the white flowers are ____________.

• Dominant

• Heterozygous

• Recessive

• Neutral

A and B are incorrect because the white flowers have a homozygous recessive genotype. The white allele is not expressed in the offspring because the dominant purple allele is present. D is incorrect because the term does not apply to this question.

​Explanation

Open Ended

Why have Mendel's experiments been so valuable?

Open Ended

Construct and explanation for why someone who grows plants might find a Punnett square to be a useful tool?