Unit 5.2 Chromosomes

• Biologie
• Middelbare school
• vwo
• Leerjaar 3

Unit 5 

Heredity and evolution

Basic 2

Chromosomes

Today

Recap 5.1

Explanation 5.2

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

Which one is correct?

1. Phenotype = genotype + environment
2. Environment = genotype + phenotype
3. Genotype = phenotype + environment

If you look at this persons hair..

1. Phenotype
2. Genotype
3. Phenotype en Genotype

Put in the correct order,
from small to big.

1. cell - chromosome - DNA - gene
2. gene - chromosome - DNA - cell
3. gene - chromosome -cell - DNA
4. gene - DNA - chromosome - cell

Body cells

The nucleus of the body cells of a human contain 46 chromosomes. 

Every chromosome carries the information for different hereditary traits. 

Chromosomes occur in pairs. 

Two chromosomes in a pair match; they carry information for the same traits. 

There are 23 pairs.

Pair 23 are the sex chromosomes. 

Pair 23 are the sex chromosomes. 

Chromosomes

Contain DNA

Bundled DNA-fibre wrapped around proteins to make it smaller and fit into the nucleus

23 chromosome pairs in human body cells

Sex cells

Sex cells are different than regular body cells = egg and sperm cells. 

 

Sex cells contain 23 chromosomes. There are no pairs. 

The child has 50% of its genetic information form the father and 50% of the mother. 

Pair 23 will determine the sex of the child. This depends of chromosome 23 of the spermcell  is a X or a Y chromosome. 

How many chromosomes?

Male or female?

45, X

How many chromosomes?

Male or female?

47, XY, +21 

fig. 3 Different information on a chromosome pair

Variation in genes

• Sex cells = no pairs of chromosomes. 
• only 1 copy of the chromosome ends up in the egg or sperm cell.
• result: variation in genotypes 

Variation in genotype

• Due to sexual reproduction.
• father 1/2 and mother 1/2 contribute 1 copy of chromosome.
• Chance/coincidence!

Each human being has 46 chromosomes. How many did you get from your mother?

1. 46
2. 23
3. 22
4. 45

A person containing an XY is a...

1. man
2. woman

A person containing the same copy of a sex chromosome is a...

1. man
2. woman

You have 23 sex chromosomes in your body.

1. True
2. False

Write down the sex chromosomes of someone who is intersex.

Let's practice 

Read basics 5.2 Chromosomes

Make the assignments 1 to 9, yes 6 as well

Extra challenge: assignment 10+11