DNA: The Genetic Material

Some Questions What makes us different from each other? Why are men typically taller than women? Why do dogs and cats have tails while humans do not?

Answer The differences are caused by the differences in DNA

DNA: Deoxyribonucleic Acid All chromosomes are comprised of the same chemical, DNA. DNA provides the directions that guide the repairing of cells and the construction of new ones.

DNA sends information from the nucleus to the various organelles in the cytoplasm using chemical messengers.

Let’s Zoom in and Take a Look at DNA!

Understanding DNA, Genes and Chromosomes Let’s use the metaphor of a library. What is needed to make a library? Books or stories What is needed to make books or stories? Words What is needed to make words? Letters

The Library Metaphor - a Summary The letters the nitrogen bases The words the genetic codes created using the nitrogen bases The books genes that are made up of a variety of genetic codes The library chromosomes that contain the genes

Each cell has a defined number of chromosomes Each cell has a defined number of chromosomes. These chromosomes are the libraries. A dog has 76 chromosomes.

A mouse has 40 chromosomes. A human has 46 chromosomes.

The DNA Molecule DNA molecules are shaped like twisted ladders. The nitrogen bases make up the rungs or steps of the ladder.

Nitrogen Bases There are 4 nitrogen bases These bases combine = specific pairs Cytosine->Guanine Thymine- >Adenine The order and the # creates all living things

Nitrogen Bases – Pairing Exercise Figure out the other strand of DNA from this strand: C= Cytosine A= Adenine G= Guanine T= Thymine *Don’t forget your base pairing rules*

Answer

QUESTION: If everybody’s DNA is made up of the same stuff (nitrogen bases), why are we all different?

ANSWER: Because the sequence of the nitrogen bases makes each DNA molecule different. This means that the chromosomes are different, which means that we are different.

INTERESTING INFO: Every person has 23 pairs of chromosomes in each cell for a total of 46. One chromosome in each pair comes from your mother and the other comes from your father. The chromosome from each parent carries the same genes.

Fingerprints are unique. That is why they are used in criminal investigations. No two sets of fingerprints are alike. DNA is similar in that it is unique. No two people have the same DNA except identical twins.

Assignement Let’s work on our base pairing rules Part A= Complete the strands with the corresponding nitrogen bases Part B= Draw and colour the strands using the base rules. The first ladder is done for you, use this as a template for the next two.