5.1 Genetics

• Biologie
• Middelbare school
• havo, vwo
• Leerjaar 3

5. It runs in the family

On inheritance, family trees, genetics and DNA

5.1 Pass it on!

How did you inherit characteristics from your parents?

Why do some inherited characteristics not show?

What are chromosomes?

Why do siblings look similar to their parents and each other?

To inherit = to receive a characteristic from an ancestor by genetic transmission. 

• Genotype = complete set of all inherited characteristics. 
• Phenotype = set of characteristics that are seen/expressed. 

           Phenotype = genotype + environmental factors. 

Chromosomes

Inside the cell nucleus are structures called chromosomes

They are DNA strands and contain all of your inherited characteristics

Normal body cell: 46 chromosomes

Organised in 23 homologous pairs. 

Each pair has two matching chromosomes. 

How can you tell this is a male karyotype? 

genotype

phenotype

XY chromosomes

cannot change!

you inherit this

can sometimes change during your life

you do not inherit this

a scar

Is not always visible

Sperm and egg cells only have 23 chromosomes. Explain why (TIP: think about what happens
during fertilisation).

What is phenotype?

1. The behavior of an organism
2. The environment an organism lives in
3. The genetic makeup of an organism
4. The observable characteristics of an organism

What is an example of a change in phenotype?

1. A tan from sun exposure
2. A genetic mutation
3. A change in personality
4. Eye color inherited from parents

5.2 

How is the gender of a baby determined?

What is the difference between the chromosomes of a sperm cell and those of an egg cell?

Mitosis and meiosis

Extra information:

Normal cell division =

mitosis 46  46 + 46 (growth, repair)

Reduction division =

meiosis 46 = 23 + 23 + 23 + 23 (gametes)

Chromosomes and karyotype:

https://www.youtube.com/watch?v=mBq1ULWJp_M 

Drag the picture to the correct word

Phenotype

Nucleus

Chromosome

DNA

This is a photograph of a set of human chromosomes, also known as a karyotype. What can you say about this person.

1. This person is male.
2. This person is female.
3. This person has Down's Syndrom (3x)
4. This is not a human karyotype.

Genotype

Phenotype

Risk for a genetic disease

LET'S PRACTISE.

A picture and karyotype of a pea plant from the species Chamaecrista fasciculata. 

3. How many chromosomes do you count?

4. Can the number of chromosomes in a pollen cell of Chamaecrista be even, uneven or both? Explain your answer!