What are we doing?

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# What are we doing? - PowerPoint PPT Presentation

What are we doing? In this activity you and your group will play the role of a 2 parents. You will work in groups of six. 3 students will play the mother 3 students will play the father

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Presentation Transcript

What are we doing?

• In this activity you and your group will play the role of a 2 parents. You will work in groups of six.
• 3 students will play the mother
• 3 students will play the father
•   You will use chromosome and gene models to create four offspring and determine their genotypes and phenotypes. Then mathematically, you will determine the probability of having offspring with different traits.

How to Use the Model

You will receive a baggie with pipe cleaners and beads.   The pipe cleaners represent chromosomes and the beads represent genes located on the chromosomes.   In humans, there are 23 pairs of chromosomes and thousands of genes, but for this exercise, we will only focus on a few.

The traits that we will focus on are:

• Sex of Child
• Hair Color (brown or blue)
• Eye Color (blonde or dark )
• Hemophilia
• Hemophilia is a sex- linked disease
• ****You will create 4 Punnett squares. One for each trait.***

For each Punnett square

the following:

1- What is the Mother’s genotype?

2- What is the Mother’s phenotype?

3- What is the Father’s genotype?

4- What is the Father’s phenotype?

5- What is the offspring's possible genotype?

6- What is the offspring’s possible phenotype?

7- For the hemophilia: Is Mom a carrier?

8- Why doesn’t Dad get an allele for this trait?

The crosses are the following:

• for sex of child: XY x XX
• for eye color of child: Bb x Bb
• for hair color of child: Dd x dd
• for hemophiliac trait : H x Hh
• (H is dominant normal)
• ( h is recessive sick gene)

Hemophilia is carried on the X chromosome. It is called an X linked genetic disorder. A women who is a carrier for hemophilia has the genetic mutation on one of her X chromosomes . She will have another non mutated X chromosome that will usually somewhat compensate for the defect in the other. It is not uncommon for women who carry the hemophilia gene to have low levels of clotting factor and have bleeding problems. A man who has hemophilia has the genetic mutation on his only X chromosome. He does not have another X chromosome to compensate for the defect so he will have hemophilia.

--The “dad” places one set of the homologous pairs (ex: that longer set) behind his back, with a chromosome in each hand.   The “mom” picks the hand she wants for the child.    Lay this chromosome on the table in front of you and set the other aside.

-- Repeat this procedure for the other homologous pair (ex: shorter set) and for the sex chromosomes.  Its should be noted that if the blue chromosome gets chosen from the sex chromosomes, the child in this cross is going to be a boy.

--Now the “mom” places one set of the homologous pairs behind her back and the male chooses.

-- The chromosomes chosen and set on the table in front of you are the genes your first child received.

Arrange the chromosomes into homologous pairs and figure out what phenotypes (appearance or trait) the offspring has.

• What is the sex of the child?   _________
• What color eyes does the child have?
• (phenotype) _______   Genotype?  ______
• What color hair does the child have? (phenotype)    _______  Genotype?   ________
• Is the child a hemophiliac? ______
• Is the child a carrier for hemophilia? _____

Data  Table

• See the data table, the first group is you and your partner.  You  are going to have 4 children.   Repeat the procedure you used to make you first child to make 3 others.
• Fill out their traits on the table.
• When you are finished, you will post your data on the board.   Other groups will also post their children’s data.   Fill out the entire chart with all the parents in the class.

Compile Data

• Total number of babies? _______
• Number of girls? _____
• Number of boys?  _____
• Number of children with brown eyes _______
• Number of children with blue eyes _______
• Number of children with dark hair ________
• Number of children with blonde hair  ______
• Number of girls with hemophilia  _______
• Number of boys with hemophilia  _______

To get the percents, divide the number you have by the total number and x 100.

Girls                         ______% Boys                       ______%

Brown eyes           ______%

Blue eyes               ______%

Dark hair                 ______%

Blonde hair              ______%

Hemophiliac boys  ______%

Hemophilac girls    ______%