5.1 Genetics

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

5. It runs in the family

What do you think of when you hear the title: 'It runs in the family'?

Which characteristics are passed on from one generation to the next?

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. 

Environmental change can also have an effect on the phenotype of us humans. Describe an example when your body would change under changing conditions

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? 

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

TALKING EXERCISE

Discuss with your classmate...

what would happen if a sex cell (egg/sperm cell) had 46 chromosomes, just like a normal body cell. What would this 

mean for the fertilised egg cell? And for the next generation?

Let's do a little inventory..

Which characteristics do you have?

Make sure you write down the results

I can roll my tongue

YES

NO

Which hand do you write with?

LEFT

RIGHT

NO PREFERENCE

Hand clasping?

Calculate the frequency in the class of tongue rolling

LET'S PRACTICE

Most people on the Solomon Islands (in the Pacific Ocean) have dark skin and dark hair. Sometimes, however, a child is born with very light-coloured hair.

Figure it out in exercise 1

Make exercise 1-5 in the online book

Finish it before next lesson

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!