U5 B3 2HVTTO

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

B3 Genes and alleles

• Take off your jacket

• Put your things on your desk

       Book, notebook, pencil case

• Bag on the floor

• Read pages 116-118

5

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Lessongoals

• Understand: I can describe what genes and alleles are by explaining their role in storing genetic information and showing how they can vary.

• Understand: I can describe what a mutation is by explaining how changes in DNA can happen and what effects they may have.

• Understand: I can describe how cancer develops by explaining how mutations can lead to uncontrolled cell division.

• Apply: I can give examples of causes of mutations, such as radiation or harmful chemicals, and link them to possible health effects.

< Mostly influenced by >

Genotype

Lifestyle

Suroundings

Phenotype

What is the difference between genotype and phenotype?

A

genotype is the information fenotype is how you look/work

B

phenotype is the information genotype is how you look/work

C

They are nearly the same thing

D

What genes are found in the cells of your liver?

A

all genes used by the liver, once

B

all genes used by the liver, twice

C

all genes found in humans, once

D

all genes found in humans, twice

What genes are found in a sperm cell?

A

All genes used by the sperm, once

B

All genes used by the sperm, twice

C

All genes found in humans, once

D

All genes found in humans, twice

A human egg cell contains ... pairs of chromosomes. (number)

DNA, how it's built

Basepair

Combination of A-T or C-G. Other combinations are impossible in the DNA

Gene

Many (often thousands) of basepairs together contain the information of a gene. The order of the basepairs decides the code and its contents.

Base

Buildingblock of the DNA, there's 4 types:

A (adenine)

C (cytosine)

T (thymine)

G (guanine)

Genes and characteristics

• Gene = (part of) the genetic code for 1 characteristic

• Genes contain information to make proteins

Example:

The colour of your skin (1 characteristic) is decided by about 16 genes.

!

This might help you understand:

You complete DNA (your genotype) = a recipe book

1 gene = a recipe from the recipe book

These recipes are used to make lots of different proteins.

These proteins are part of your body and make it function.

!

Alleles

Allele = a version/variant of a gene

Gene = characteristic         allele = version of characteristic

Examples: 

Gene              Alleles

Eye colour     blue, green 

Hair shape     straight, curly

Height            tall --- short

Skin colour.   black --- white

Feet size         40, 42

Earlobe.          attached, loose

If you compare genes > alleles to other things:

Tree > oak

Dog > labrador

Cat > siamese

Flower > rose

A chromosomepair is shown, Gene A is indicated on both chromosomes.

This gene contains information for the same characteristic.

The colours are different, indicating the alleles are different.

This means the information contained in the genes is different

A

A chromosomepair is shown, Gene B is indicated on both chromosomes.

This gene contains information for the same characteristic.

The colours are the same, indicating the alleles are the same.

This means the information contained in the genes is the same

A

Allele pairs

Alleles of 1 gene form pairs:

• 2 same alleles = homozygous

• 2 different alleles = heterozygous

You have 2 sets of each gene (1 from mother, 1 from father)

This means you have 2 alleles for each gene.

1 allele from your father, the other is given by your mother.

These alleles can be the same or different.

!

Which is an allele that has to do with hair?

A

Hair colour

B

Blond

C

Hair shape

D

Blue

Which cells contain alleles for hair colour? Pick the answer showing the most correct cells

A

Hair cells

B

Hair and head cells

C

Hair, head and brain cells

D

Hair, head, brain and eye cells

Which allels could you both find in the same sperm cell?

A

Brown hair Blond hair

B

Blue eyes Green eyes

C

Brown hair Blue eyes

D

Red hair Blond hair

Mutations

• The genotyp of a person can not change

• Mutation = part of the DNA (in a cell) changes

• Mutations during your life: little to no influence

• Mutation in sex cell that becomes you: mutant

Mutant = organism in which mutation is visible in phenotype

All cells of the organism contain the mutation

example: albino

In almost all cases, the mutated cell dies shortly after mutation.

Because of this, it doesn't cause problems.

If this doesn't happen, cancer is usually what happens

How does DNA mutate?

Mutations can be caused by mutagenic influences:

• Sunlight (UV-radiation)

• Radioactive radiation (Röntgen)

• Asbestos, smoke

Mutations also happen by mistake during cell division

Cancer, how and why?

• Happens due to mutations, Not bacteria/virus

• Mutation makes cells divide continously      

• this creates a tumour:

       - Benign: Divides slowly, stays at its spot

       - Malignant: divides quickly, disrupts tissues

• Metastasis > cancer cells are carried by blood/lymph. End up in different body parts and create more/new tumours

Zs = Working in Silence

• No asking questions

• Silent, don't disturb anyone

• Stay at your  desk

What you should do: U5 B3

• Pages  116-122

• Asgmt  1-8 (4)

OR challenge

• Asgmt 5-10

Done with the above?

• Work on the next chapter(s)

• Learn for the test 

• Make other homework

• Read a book

6

minute

00

second

add30s

What you should do: U5 B3

• Pages 116-122

• Asgmt 1-8 (4)

OR challenge

• Asgmt 5-10

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

Tim says: This dog is homozygous This isn't (entirely) correct, what should he add or change to this sentence?

Tidy Duty

3 people each lesson

• Desks: empty and straight

• Chairs:  underneath the desks OR end of day: on the desks

• Floor: no rubbish