Warm- UpBrown fur is dominant to white fur in a type of

bunny. Draw a Punnett square to show a cross between a homozygous recessive

dad and a heterozygous mom.

1. What genotype(s) in the offspring will code for brown fur?

2. What is the probability that their bunnies will have white fur?

Agenda• Objectives: SWBAT: Analyze a dihybrid

cross to determine the probability of a particular trait, given completed Punnett square– Go over and turn in homework– Notes– Stepwise Dihybrid crosses– Exit Ticket

• Calendar– Quiz Thursday

Friday’s Homework

Steps to solving genetics problems

1. Identify the letter you’ll use.

2. Write the genotypes of the parents.

3. Draw the Punnett Square.

4. Determine the possible genotypes and phenotypes of the offspring.

5. Determine the probability of a given genotype or phenotype.

COPY THE STEPS!

Steps to solving genetics problems

1. Identify the letter you’ll use. (B)

2. Write the genotypes of the parents. (bb, Bb)

3. Draw the Punnett Square.

4. Determine the possible genotypes and phenotypes of the offspring. Bb= brown, bb= blue

5. Determine the probability of a given genotype or phenotype.

For each Punnett Square that we’ve done, how many traits did we study?

Monohybrid Crosses

• Up to this point, we have only been looking at monohybrid crosses– Two parents are mated (hybrid)– We only examine one trait (mono)

• Today we’re going to start looking at dihybrid crosses

What is a Dihybrid Cross?

a. “Di” means two

b. In a dihybrid cross– Two parents are mated (hybrid)– We examine two traits (di)

A dihybrid cross is used to determine the possible offspring of two parents based on two traits.

c. In this example:• Tail length is

indicated by S for short tail or s for long tail.

• Coat color is indicated by B for brown coat or b for white coat while

Steps to solving genetics problems

1. Identify the letter you’ll use.

2. Write the genotypes of the parents.

3. Draw the Punnett Square.

4. Determine the possible genotypes and phenotypes of the offspring.

5. Determine the probability of a given genotype or phenotype.

COPY THE STEPS!

Answer the questions in your notes section

Short Tail is dominant to long tail

Brown fur is dominant to white fur

1. What are the possible genotypes for a cat with a short tail? Use the letter “S”

2. What are the possible genotypes for a cat with brown fur? Use the letter “B”

3. What are the possible genotypes for a cat with a long tail? Use the letter “S”

4. What are the possible genotypes for a cat with white fur? Use the letter “B”

Practice Questions

5. How many boxes show a cat with brown fur?( ____ / 16)

6. How many boxes show a cat with white fur?

7. How many boxes show a cat with a long tail?

8. How many boxes show a cat with a short tail?

9. What are the possible genotypes for a cat with a long tail and white fur?

10. What are the possible genotypes for a cat with long tail and brown fur?

11. What are the possible genotypes for a cat with a short tail and white fur?

12. What are the possible genotypes for a cat with short tail and brown fur?

Practice Questions

13. How many boxes show a cat with white fur and a long tail?

14. How many boxes show a cat with brown fur and a long tail?

15. How many boxes show a cat with white fur and a short tail?

16. How many boxes show a cat with brown fur and a short tail?

How do we fill in a Dihybrid Cross?

• http://www.dnaftb.org/5/problem.html

Dihybrid practice sheet

Exit Ticket

1. What are the possible genotypes for a yellow, wrinkled seed?

2. What’s the probability that a seed will be yellow and smooth?

Warm Up1. What is a family tree?

2. What’s the difference between a dihybrid cross and a monohybrid cross?

3. What are the possible genotypes for a yellow, wrinkled seed?

4. What’s the probability that a seed will be yellow and smooth?

Agenda• Objectives: SWBAT: Identify the sex

chromosomes in humans and recognize inheritance patterns that are sex-linked, using a pedigree or scenario– Notes– Human Chromosome Sheet– Pedigree Practice– Exit Ticket

• Reminder– Quiz Thursday!

Chromosomesa. The sex chromosomes are the 23rd pair

of chromosomes.

b. The other 22 pairs of chromosomes are called autosomes.

c. Traits or diseases can be either sex-linked or autosomal

What are Pedigrees?

a. Pedigrees- chart- show how a trait is

passed down over several generations

- Can show autosomal or sex-linked traits

b. Pedigrees look like family trees

Example

What are the Sex chromosomes?

a. The 23rd pair of chromosomes determine your sex.

b. There are two different sex chromosomes: X and Y

c. Females have the chromosomes XX

d. Males have the chromosomes XY

e. Where do we get the first X chromosome from?

What are Sex-Linked Traits?

a. Certain traits are called sex-linked because the traits are determined by genes on the X and Y chromosomes (the sex chromosomes).

b. Most sex-linked traits are only found on the X chromosome.

c. Genetic diseases or mutations are carried on the X chromosome.

- Females are more likely to be carriers because they have two X chromosomes

- Males are more likely to inherit genetic diseases because they only have one X chromosome

- Example: Red/Green Colorblindness occurs in 1 out of 10 males in the US and 1 out of 100 females in the US.

What are the Sex chromosomes?

Look at Chromosome Chart

Warm UpYellow seed color (Y) is dominant to green seed color (y), and round seeds (R) are dominant to wrinkled seeds (r). A plant that is homozygous for green, wrinkled seeds is crossed with a heterozygous yellow and round plant. Draw the dihybrid cross. What’s the probability that they will produce plants with yellow, wrinkled seeds?

Agenda• Objectives: SWBAT: Identify the sex

chromosomes in humans and recognize inheritance patterns that are sex-linked, using a pedigree or scenario

• Pedigrees• Complete Practice Sheet• White Board Practice (If there’s time)• Exit Ticket• Gather materials for Quiz

Examine a Pedigree

Pedigree Worksheet

Put together packet• Phenotype Study• Genetics Review 1• Reading guide 6.3• Punnett Squares- Crosses involving one trait• Bill Nye Video Questions• Punnett Square Worksheet• Human Chromosomes• Bikini Bottom Genetics (I still have those that

were turned in)

Warm Up

1. What’s the phenotype of person #3?

2. What’s the genotype of person # 4?

3. Who are the children of person’s 1 and 2?

Agenda

• White Board Review• Turn in packets• Quiz• Video

Draw the symbol for carrier female

• In bunnies, brown fur (B) is dominant to white fur (b) and short fur (S) is dominant to long fur (s).

1. What would be the genotype of a heterozygous brown bunny with short fur?

2. What about a homozygous white bunny with short fur?

• If brown fur is dominant to white fur and short fur is dominant to long fur, what’s the probability that the offspring will be brown with short fur?

Write the genotype of a male with hemophilia (which is caused by a recessive gene on the X chromosome)

A heterozygous tall plant is crossed with a short plant. The tall gene is dominant to the short gene in plants. What’s the probability that the offspring will be tall?

What percent of the offspring are homozygous recessive?

 GG

 Gg

Gg

 gg

If the dominant fur color is gray and the recessive fur color is black, what’s the probability of the offspring having gray fur?

 GG

 Gg

Gg

 gg

In certain breeds of dogs, deafness is due

to a recessive allele (d) of a particular gene, and normal hearing is due to its dominant allele (D). What percentage of the offspring of a normal heterozygous (Dd) dog and a deaf dog (dd) would be expected to have normal hearing?

The following genotypes were found in a male cat and a female cat: BbSs (male) bbSS (female)

Which one of the following choices is true of the phenotype of offspring from these parents?

a. All offspring will have black fur.

b. All offspring will have white fur.

c. All offspring will have long-haired fur.

d. All offspring will have short-haired fur.

Hemophilia is a sex-linked recessive disease. If a woman has a genotype

XRXr does she have hemophilia?

If a man is XrY does he have hemophilia?

A woman is XRXr and a man is XrY, what’s the probability that their children will have hemophilia?

A man with a widow’s peak marries a woman with a straight hairline. Use the letter “H”

• If one of his parents had a widow’s peak and the other did not, what is his genotype?

• What’s the probability that they will have children with a widow’s peak?

A pregnant couple wants to know if their child will have curly hair. Having curly hair is a dominant trait. The mother has the prettiest curls and so do her parents. The father however, has straight hair. What’s the probability that their child will have curly hair?

Autosomal or sex-linked disorder?

Autosomal or sex-linked disorder?

Clean up White Boards

• Turn in your markers and white boards

• Spread yourselves out around the classroom for the quiz

Cracking the code

• http://www.pbs.org/wgbh/nova/body/cracking-the-code-of-life.html

Warm Up

1. What are some traits that can be passed down in a family?

2. Are all traits inherited the same way? Explain what you think in complete sentences.

Agenda

• Objectives: SWBAT Define and distinguish between different modes of inheritance.

• Look at different scenarios of inheritance• Worksheet • DNA Cracking the Code Video

Scenario 1

Tay-sachs disease is caused by a recessive gene on chromosome # 15. If two parents are carriers for the disease, they have a 25% chance of having a child with the disease.

Scenario 2

• The lubber grasshopper is black with red and yellow stripes. Lubber grasshoppers are produced when a grasshopper with yellow stripes mates with a grasshopper with red stripes. Red stripes are expressed with the homozygous dominant (RR) genotype, yellow stripes with the homozygous (rr) genotype, and red and yellow stripes with the heterozygous (Rr) genotype.

Scenario 3

• Suppose you have two rose plants, both with pink flowers. You cross the two plants and are surprised to find that, while most of the offspring have pink flowers, one has red flowers and another one has white flowers.

Scenario 4

• Queen Victoria's eldest daughter, Victoria, apparently escaped the hemophilia gene as it did not appear in any of her descendants. Victoria's fifth child, Helena may have been a carrier because two healthy sons survived to adulthood but two other sons died in infancy and her two daughters did not have issue. Her son Leopold suffered from hemophilia and her daughters Alice and Beatrice were confirmed carriers of the gene.

Scenario 5

• There is a wide range of different eye colors in humans. Someone can have very dark, almost black eyes. Another person can have light brown eyes. There are different shades of blue eyes person can have, some are bright and some are more gray. Why is there so much variation?

Exit ticket• Say the following chart shows a pedigree of

hemophilia within a family. Identify the sex and whether or not the person has hemophilia1. Person 1

2. Person 6

3. Person 12