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? 

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).

A rhesus monkey has 46 chromosomes. How many chromosomes in its sex cell?

1. 46
2. 23
3. 44
4. 22

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

Can you change the phenotype of in individual?

1. Yes
2. No
3. Don't know

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

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?

Talking point

Long ago, a king would blame his wife if she had given him only daughters and no sons. He could divorce her and take a new wife who, he thought, could give him a son. This is because only a son could succeed his father to become the new king someday. Discuss with another student why the king was wrong to blame his wife. What biological reason would you give the king in order to change his mind? Also: What are the chances of getting a baby boy? And a baby girl?

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 

1. Watch the video and make a short summary

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!