U5 B8 2HVTTO

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

B8 Dominant and recessive

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

       Book, notebook, pencil case

• Bag on the floor
  
• Read pages 164-165

Lessongoals

• Understand: I can explain that genes can exist in different forms called alleles, and describe the difference between dominant and recessive alleles.
• Analyse: I can explain how alleles affect the phenotype in both homozygous and heterozygous combinations by using correct examples.
• Apply: I can use gene symbols to write down genotypes and fill in simple Punnett squares to predict the offspring's genetic combinations.

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

What is the best description of genes and alleles?

1. A gene is in the DNA An allele is on a chromosome
2. a gene is a characteristic an allele is a variant of this characteristic
3. allele and gene are synonymous
4. an allele is a characteristic a gene is a variant of this characteristic

Give an example of a gene

Healthy organisms always have 2 alleles of each gene.
Explain why these alleles aren't always the same.

Homo- & heterozygous

Homo = same            hetero = different

Homozygous > alleles for the characteristic are the same 

Heterozygous > alleles of the characteristic are different

A man and woman have a baby.
The man is homozygous for blond hair.
The woman is homozygous for brown hair.
Explain, will the baby be homozygous or heterozygous for hair colour?

Dominant and recessive

• Alleles are either dominant or recessive
• Dominant is 'stronger' than recessive
• A dominant trait means dominant for all members of the species
• Heterozygous genotype > Dominant allele visible in phenotype

Example:

If blond is dominant over brown hair, it means that for every human blond is dominant!

It doesn't differ per human (or animal/plant/etc.) if a certain allele is dominant or recessive!

There are 3  possibilities:

• Heterozygous = 1 recessive allele and 1 dominant allele > dominant phenotype
• Homozygous dominant = 2x dominant allele > dominant phenotype
• Homozygous recessive = 2x recessive allele > recessive phenotype

Cats can have black or red fur colour.
Black is dominant.
What are possible genotypes for a black cat?

1. Always homozygous
2. Always heterozygous
3. Homozygous or heterozygous

Cats can have black or red fur colour.
Black is dominant.
What are possible genotypes for a red cat?

1. Always homozygous
2. Always heterozygous
3. Homozygous or heterozygous

Flowers of the bean plant can be pink or white.
Plant 1 has white flowers and is heterozygous.
Plant 2 has pink flowers and is homozygous.
Which colour is recessive?

1. White
2. Pink
3. Impossible to know

Gene symbols

Alleles are usually shown using a letter.

• Alleles of the same gene use the same letter
• Dominant = capital letter,  Recessive = normal letter
• AA = homozygous dominant
• aa = homozygous recessive
• Aa = heterozygous

Often the letter A is used. But other letters are also possible.

If the choice is yours, be sure to use a letter where capital and small are clearly different! like:

• Bb
• Gg
• Rr

Sometimes people write aA instead of Aa.

Always put the capital letter first! in a homozygous genepair.

(it shows that dominant is the strongest)

Alleles in body cells and sperm cells (sex cells) of the father

Alleles in body cells and egg cells (sex cells) of the mother 

Possible allele pairs in fertilized egg cells and body cells of the offspring of these parents

Mix the alleles

Try making lots of different correct combinations

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

Flowers of the beanplant can be pink or white.
Plant 1 has white flowers and is heterozygous.

Use gene symbols to show the genotype of this flower.
Use the first letter of the dominant allele

For humans, red hair is dominant over blond hair.
A man is heterozygous for hair colour.
What is his geno- and phenotype?

1. AA and red hair
2. aa and blond hair
3. Aa and red hair
4. Aa and blond hair

A father has genotype AA, the mother Aa.
Which genotypes are possible for their kids?

1. AA, aa en Aa
2. Aa en aa
3. Aa en AA
4. aa en AA

1st choice: + OR Cheat sheet +1 cm2 OR Wheel

2nd and 3rd choice: Cheat sheet +1 cm2 OR Wheel

4th en 5th: Wheel 

TTO

What you should do: 5.8

• Read pages 164-166
• Do asgmt  1-3 pgs. 163-165
• Challenge: how it fits together pgs. 158-159 

Done with the above?

• Work on the next chapter(s)
• Learn for the test 
• Make other homework
• Read a book

Zs = Working in Silence

• No asking questions
• Silent, don't disturb anyone
  
• Stay at your  desk

What you should do: 5.8

• Read pages 164-166
• Do asgmt 1-3 pgs. 163-165
• Challenge: how it fits together pgs. 158-159 

Done with the above?

• Work on the next chapter(s)
• Learn for the test 
• Make other homework
• Read a book

Zw = Working with whispering

• Teacher is available for questions
• Only whisper with the student next to you
• Stay at your  desk

2 Parents both have blue eyes.
They have a son with green eyes.

What is (probably) the genotype of the parents and son?
Use gene symbols

Tidy Duty

3 people each lesson

• Desks: empty and straight
• Chairs:  underneath the desks OR end of day: on the desks
• Floor: no rubbish