1. Structure and Replication Part 1 - DNA

2. DNA Deoxyribonucleic Acid
DNA contains all the instructions for all the traits of a living organism.
What is a trait?
Images: MSOffice Powerpoint

3. DNA DNA is found in the nucleus of a cell.
DNA makes up the chromosomes.
Humans have 23 pairs of chromosomes in the nucleus of each cell.
This is a picture of the chromosomes found in every human cell. Notice how there are 23 matching pairs. The last two determine the gender. XY means this is a boy.

4. Don’t forget! Those are all traits!
Genes
A gene is a small segment of DNA.
Genes have the instructions for all the traits in an organism.
Genes “code” for such traits as eye color, hair type, skin color, height, and even diseases.
Don’t forget! Those are all traits!
Images: MSOffice Powerpoint

5. Let’s label!

6. Discovery of DNA
Several scientists are given credit with the discovery of DNA.
James Watson and Francis Crick discovered DNA in 1952.
Rosalind Franklin also helped discover DNA.

7. Structure and Replication Part 2- Structure
DNA
Structure and Replication
Part 2- Structure

8. Structure of DNA DNA resembles a “twisted ladder”
DNA is made up of many nucleotides.
One nucleotide has 3 parts:
1. Phosphate
2. Sugar (Deoxyribose)
3. Base
There are four types of bases:
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

9. Structure of DNA
The Phosphates (P) and Sugars (D) make up the sides of the DNA “ladder”.
The bases (A, T, C, G) make up the rungs (steps) of the ladder.

10. Nucleotides Nucleotides will only join in very specific ways.
This is similar to a jigsaw puzzle. Only certain pieces fit together.
Adenine (A) only bonds with Thymine (T)
Cytosine (C) only bonds with Guanine (G)

11. When DNA is untwisted, it looks much like a ladder.
Notice how the sides of the ladder are alternating sugar and phosphate molecules.
The rungs (steps) are the nitrogen bases.
Also notice how G always pairs with C.
And A always pairs with T
Image courtesy of Jennifer Richardson

13. Making more DNA
During mitosis and meiosis (cell division) DNA gets copied before a cell divides.
Notice in the picture that the left side of the DNA molecule is identical to the right side.
A always joins with T
C always joins with G
(like puzzle pieces)

14. Structure and Replication Part 3- Replication
DNA
Structure and Replication
Part 3- Replication

15. Replication
DNA replication is a process that copies the DNA in the nucleus of a cell before it divides.
This is so each new cell will have a complete set of DNA.
Replication happens during mitosis and meiosis.
Replication makes sure that every new cell will have instructions for how to work.

16. The steps of DNA Replication
DNA molecule “unzips” by breaking the bonds that hold the bases (A,T,C,G) together.
New bases (shown in blue below) are added to each strand of the DNA.
Notice that the two new strands are identical to each other.

17. http://www. woisd. net/moodle/file. php/6/assets/images/ks4/dnacopy

18. __ __ __ __ __ __ __ __ __ __ __
You practice!
Which bases would match the following DNA strand during DNA Replication?
G C A T A T G G T C A
__ __ __ __ __ __ __ __ __ __ __
Hint:

19. The Answer! G C A T A T G G T C A C G T A T A C C A G T
Which bases would match the following DNA strand during DNA Replication?
G C A T A T G G T C A
C G T A T A C C A G T
Hint: