Genes and alleles

• Biologie
• Middelbare school
• havo
• Leerjaar 2

Welcome!

Today:

Questions about 5.2

Explanation about genes and alleles (paragraph 5.3, page 118)

Making homework 

The chromosomes of the same pair have the same genes but different variations of them.

1. True
2. False

A human cell has 23 chromosomes, so it must be a...

1. Body cell
2. Sex cell

A cell of a random organism has 7 chromosomes, this must be a...

1. Sex cell
2. Body cell

A cell of a random organism has 17 pairs of chromosomes. This must be a...

1. Body cell
2. Sex cell

What are we going to learn today?

We are going to learn:

How DNA is structured.

What genes and alleles are.

What happens when your DNA changes. 

Building your genotype

DNA

DNA consists of 2 strands, built up with phosphorus and sugar. However, between these strand you will find bases. There are 4 variants of these: A, T, C and G. Every connection between strands consists of 2 bases: A is always attached to a T, a C is always attached to a G. 

DNA 

Genes and alleles 

A piece of DNA that says something about one characteristic is called a gene, like a gene for hair color, height or heightened risk for a certain disease. 

A gene can have several variations. These are called alleles. You always get two per characteristic: one from your mom and one from your dad. 

Variants of genes: alleles 

Both alleles are as strong 

Mutations

DNA can change from time to time for several reason. The consequences resulting from that change range from non-existing to life changing. A mutation in a body cell is often less dangerous than a mutation in a sex cell. That's because two sex cells determine the whole genotype of a new life. 

Example 1: Albinism

Example 2: cancer

One mutation can result in cells dividing rapidly, using a lot of your body's resources. This is called a tumour. Tumours can stop growing at one point, but when they don't they are called malignant. They keep growing and growing. When this happens you have cancer. A next stage in cancer is metastasis, where the cancer spreads through your circulatory or lymphatic system to other organs. 

Stages of cancer 

Causes for mutations (mutagenic influences)

Get to work!

The homework for next lesson are the exercises of paragraph 5.3, starting on page 122. You also need to make the summary. You can start with them now.