U5 B2 2HVTTO

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

B2 Chromosomes

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

       Book, notebook, pencil case

• Bag on the floor
  
• Read pages 106-108

Lessongoals

• You can explain how each of the parents provides 50% of the chromosomes
• You can explain how the sex of a human is determined by sex chromosomes
• You can explain how sexual reproduction causes variation in genotypes

Wheel of homework

Go to Lessonup.app and use this code

Reward

Penalty

DNA in the cells of the intestines, also contains genes for hair color

1. True
2. False

During summer, Jack likes to do lots of sunbathing. Because of this, he gets a tan.
What has happened?

1. His genotype has changed
2. His phenotype has changed
3. His genotype and phenotype have changed
4. His genotype and phenotype stay the same

How many chromosomes can you find in the nucleus of an eye cell? (number)

Do all cells in the body of a grown up healthy human contain 46 chromosomes?

1. Yes, all cells
2. No, but nearly all of them do
3. No, about half of them
4. No, only some cells

Chromosomes form pairs.

1 pair contains information for the same hereditary characteristics.

1 pair contains the same genes 

(2 'versions', 1 on  each chromosome)

What is a gene?

A pair of chromosomes

These genes contain different information

Genes

Every coloured ring is 1 gene on the chromosome.

Some genes are bigger than others, they might contain more information.

Genes contain information about (part of) 1 characteristic.

The same characteristic can also have different variants.

example: Blue or green eye colour

When genes are shown with same colours, it means the gene contains the same information, 

example: both contain the information for blond hair.

When the colours differ, it means  the information in the gene is different. These are variants of the gene

example: one contains information for blond hair, the other for  ginger hair

Every (healthy) human has 2 versions of each gene.
Why do we have 2 versions of each gene?

Sexual reproduction

• Sperm/ova are made during a special cell division: meiosis. 
• Meiosis randomly splits all chromosome pairs, giving each daughter cell only 1 of each pair.
• Lots of different chromosome combinations are possible
• During fertilization two sex cells combine, creating new chromosome pairs

Sex

• Decide by X, Y chromosome
• XX = female
• XY = male
• Intersex : XX or XY
• Why is YY impossible?

Male or female?

Male

Female

Sperm

Ova

Chromosomes of father

Chromosomes of mother

What you should do:

• Read pages  106-109
• Do asgmt  1-8 pgs. 109-112
• Challenge: 9, 10, 11 

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:

• Read pages 106-109
  
• Do asgmt 1-8 pgs. 109-112
  
• Challenge: 9, 10, 11 

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

Tidy Duty

Today these people are on tidy duty

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