U5 Punnet Squares 2HVTTO

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

5.Punnett squares

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

       Book, notebook, pencil case

• Bag on the floor

Lessongoals

• Analyse: I can draw conclusions from a story or context about whether an allele is dominant or recessive, or what the genotype of the parents or children is.
• Apply: I can make simple genetic crosses using a Punnett square to determine which genotypes are possible in the offspring of two parents.
• Evaluate: I can use a Punnett square to calculate the probability of a specific genotype or phenotype appearing in the offspring by working out correct ratios or percentages.

Wheel of homework

Go to Lessonup.app and use this code

Reward

Penalty

Rewards

• S = you get to make a cheatsheet for a test. Starts being 1 by 1 cm. Everytime you earn an S it gets 1 cm bigger to a max of 5 by 5 cm.
• + = If you earn this 3 + you get to add 0,5 to one of your biology marks.
• Snitch = You can pick a classmate who also is checked for homework
• ✔ = When you earn 3 ✔ you can turn them into a + or S
  

penalties

• 45 min extra worktime = you need to come after school and do homework, this will last for 45 min or until the task is done
• Coloringpage = You get to pick a coloringpage, You need to color it and perform tasks that might be on it. You need to hand it in during the next lesson, If you don't you get 2 marks.
• X = if you get 3 of these you will automaticly earn the 45 min extra worktime.
• Snitch = You can pick a classmate who also is checked for homework
• Lucky! = You don't get a 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 alleles of the trait?
2. Which allele 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

Blond is dominant.

The father is homozygous and has brown hair

The mother is homozygous and has blond hair. 

If these parents have a 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 alleles of the trait?
2. Which allele 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

Blond is dominant.

The father is homozygous and has brown hair

The mother is homozygous and has blond hair.

If these parents have a child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different alleles of the trait?
2. Which allele 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

Blond is dominant.

The father is homozygous and has brown hair

The mother is homozygous and has blond hair.

If these parents have a child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different alleles of the trait?
2. Which allele 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

Blond is dominant.

The father is homozygous and has brown hair

The mother is homozygous and has blond hair.

If these parents have a child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different allele of the trait?
2. Which allele 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

Blond is dominant.

The father is homozygous and has brown hair

The mother is homozygous and has blond hair.

If these parents have a child, what are the chances that this kid has brown hair?

Mother

steps

Follow these steps:

1. What are the different allele of the trait?
2. Which allele 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 allele of the trait?
2. Which allele 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 alleles of trait eyecolour
2. .
3. 
   

steps

Follow these steps:

1. What are the different alleles of the trait?
2. Which allele 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

How can you know?

The story clearly states that the possibilities are blue and brown

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 alleles of trait eyecolour
2. Blue must be dominant, making brown recessive
3. 
   

steps

Follow these steps:

1. What are the different alleles of the trait?
2. Which allele 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

How can you know?

The story clearly states that the possibilities are blue and brown

How can you know?

Brown must be recessive. Because if brown where dominant, than at least 1 of the parents should also have brown eyes. And this is not the case!

The only way in which the phenotype of the child can be different from both parents. is that that phenotype is recessive

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 alleles 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 alleles of the trait?
2. Which allele 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

How can you know?

The story clearly states that the possibilities are blue and brown

How can you know?

Brown must be recessive. Because if brown where dominant, than at least 1 of the parents should also have brown eyes. And this is not the case!

The only way in which the phenotype of the child can be different from both parents. is that that phenotype is recessive

How can you know?

Because the child has brown eyes, he must have a homozygous recessive genotype: aa

This means that both parents need to be able to give the child one a.

But because both parents are showing the dominant phenotype, they must also have at least 1 A. 

The only possible genotype for both parents is heterozygous: Aa.

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 alleles 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 alleles of the trait?
2. Which allele 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 alleles 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 alleles of the trait?
2. Which allele 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 alleles 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 alleles of the trait?
2. Which allele 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!
• Use this site to try different combinations and see chances 

Tidy Duty

Today these people are on tidy duty

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