U5 Punnet Squares 2HVTTO

• Biologie
• Middelbare school
• havo, vwo
• Leerjaar 2

Punnet squares

• Take off your jacket
• Put your things on your desk

       Book, notebook, pencil case

• Bag on the floor

Lessongoals

• You can draw conclusions about the dominance/recessiveness of a particular allele or the genotype of the parents/children from a story.
• You can perform simple crosses using a Punnett square to determine the possible genotypes in the offspring of two parents.
• You can use Punnett squares to make predictions about the likelihood of a specific genotype or phenotype occurring in the offspring of two parents.

Wheel of homework

Go to Lessonup.app and use this code

Reward

Penalty

A person is heterozygous for his eyecolour. His genotype for this trait is.

1. AA
2. A or a
3. aa
4. Aa

Two parents with blond hair have a kid who has brown hair.
The genotype of the kid must be

1. Aa
2. AA
3. aa

Crossings/using punnet squares

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

Example

Question: Two parents have a child with blond hair. The father is homozygous and has brown hair and the mother is homozygous and has blond hair. If these parents have another child, what are the chances that this kid has brown hair?

Do steps 1,2 and 3

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

Example (continued)

Father

Question: Two parents have a child with blond hair. The father is homozygous and has brown hair and the mother is homozygous and has blond hair. If these parents have another child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

Make a punnet Square.

Make a table as shown.

Add mother and father (or the names if you know them)

4

Example (continued)

	a	a
A
A

Father

Question: Two parents have a child with blond hair. The father is homozygous and has brown hair and the mother is homozygous and has blond hair. If these parents have another child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

Fill in possible alleles for both parents.

You can get these from the genotypes. Just put each letter of the genotype in their own box

5

Example (continued)

	a	a
A	Aa	Aa
A	Aa	Aa

Father

Question: Two parents have a child with blond hair. The father is homozygous and has brown hair and the mother is homozygous and has blond hair. If these parents have another child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

Make combinations

Add the letters of the parents together where they meet in the table.

6

Example (continued)

	a	a
A	Aa	Aa
A	Aa	Aa

Father

Question: Two parents have a child with blond hair. The father is homozygous and has brown hair and the mother is homozygous and has blond hair. If these parents have another child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

All four genotypes are heterozygous, they will all have blond hair. The odds for brown hair are 0%

Answer the question

7

Choose

Pick one:

• Want to try on your own? Go practice in silence. 

Go to joinmyquiz.com and use the code given.

• Need more help to understand crossings? We'll practice more together!

Example 2

Two parents both have blue eyes, their first child has brown eyes. 

What are the chances for their kids to be heterozygous for this trait?

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

Example 2

Two parents both have blue eyes, their first child has brown eyes. 

What are the chances for their kids to be heterozygous for this trait?

Answer:

1. Blue and brown are possible forms of trait eyecolour
2. Blue must be dominant, making brown recessive
3. Father and mother are both heterozygous having genotype Aa

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

Example 2

Two parents both have blue eyes, their first child has brown eyes. 

What are the chances for their kids to be heterozygous for this trait?

Answer:

1. Blue and brown are possible forms of trait eyecolour
2. Blue must be dominant, making brown recessive
3. Father and mother are both heterozygous having genotype Aa
4. >
5. >

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

	A	a
A
a

Mother

Father

Example 2

Two parents both have blue eyes, their first child has brown eyes. 

What are the chances for their kids to be heterozygous for this trait?

Answer:

1. Blue and brown are possible forms of trait eyecolour
2. Blue must be dominant, making brown recessive
3. Father and mother are both heterozygous having genotype Aa
4. >
5. >
6. >

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

	A	a
A	AA	Aa
a	Aa	aa

Mother

Father

Example 2

Two parents both have blue eyes, their first child has brown eyes. 

What are the chances for their kids to be heterozygous for this trait?

Answer:

1. Blue and brown are possible forms of trait eyecolour
2. Blue must be dominant, making brown recessive
3. Father and mother are both heterozygous having genotype Aa
4. >
5. >
6. >
7. 2 of the 4 possible genotypes are heterozygous. That

        means there is a 50% chance

steps

Follow these steps:

1. What are the different forms of the trait?
2. Which form is dominant/recessive?
3. What are the genotypes and phenotypes of the parents
4. Make a Punnet square
5. Fill in possible alleles of parents
6. Make combinations
7. Answer the question

	A	a
A	AA	Aa
a	Aa	aa

Mother

Father

Choose

Pick one:

• Do you understand? Go practice on your own in silence. 

Go to joinmyquiz.com and use the code given.

• Need more help understanding crossings? We'll practice more together!

TTO

Tidy Duty

Today these people are on tidy duty

• Desks: empty and straight
• Chairs:  underneath the desks
• Floor: no rubbish