1. DNA Replication

2. What does DNA stand for? D = deoxyribo + N = nucleic + A = acid
Put it all together and it spells-
deoxyribonucleicacid

3. What is DNA Replication?
Process by which-
a cell makes a copy of the DNA in its nucleus.

4. When does DNA Replication occur?
Before Mitosis begins- Interphase
Cell Division: Stage1- Interphase

5. Why is DNA Replication an important cell process?
Ensures that each daughter cell will have all of the genetic information it needs to carry out its activities.
Forming daughter cell
DNA (genetic information)
Forming daughter cell
DNA (genetic information)

6. History of DNA’s Discovery
* 1950’s scientists showed DNA carries all cell’s instructions.
* Learned DNA passed from parent cell to its daughter cells.
* 1953 James Watson and Francis Crick discovered structure of DNA.
- Revealed important information about how DNA copies (replicates) itself.

7. Appearance of DNA Looks like spiral staircase or twisted ladder
Often called “double helix”
helix-
shape that twists like threads of a screw

8. Structure of DNA Sides (DNA Ladder) Rungs (DNA Ladder)
Phosphate
Sides (DNA Ladder)
Alternating molecules of
Deoxyribose sugar
Phosphate
Rungs (DNA Ladder)
Made up of pairs of nitrogen bases
adenine
thymine
cytosine
guanine
Deoxyribose sugar
Nitrogen base

9. Ladder Rungs Letters A, T, G, C
Used to represent the four bases that make up ladder’s rungs
Nitrogen bases on one side of ladder “match up” in specific way with bases on the other side.
Adenine always pairs with Thymine (A-T)
Guanine always pairs with Cytosine (G-C)
Nitrogen Base
Nitrogen base

10. Pairing pattern of the nitrogen bases
key to understanding how DNA replication occurs.

11. Replication Process Step 1:
Two sides of the DNA molecule unwind and separate between paired nitrogen bases on each rung.
Like a zipper unzipping

12. Replication Process Step 2:
Nitrogen bases floating in nucleus pair up with bases on each half of the DNA molecule.
A always pairs with T
G always pairs with C

13. Replication Process Step 3:
Once new bases are attached, two new DNA molecules formed.
Order of bases in each new DNA molecule exactly matches the order in the original molecule.

15. Chromatin
DNA wraps around proteins and takes the form of chromatin, it looks like loose coils or spaghetti, very long. In the nucleus.

16. Chromosome X- shaped structures composed of tightly coiled DNA
One comes from the mother and one comes from the father.
This happens during cell division.
They will attach in the middle, which forms a Gene.

17. Gene

19. Lab Marshmallow DNA Replication Applying What You Have Learned:
Write down a code of 5 base pairs
Ex: A-T, T-A, G-C, G-C, T-A
Using colored marshmallow make your base pairs and place them in the order of your code
Green = Adenine Yellow= Thymine
Pink = Guanine White = Cytosine
Use a broken demonstrated shown
Make sides of ladder, as demonstrated
Deoxyribose =
Phosphate =

20. Base-Pairing Mini-Lab Materials
Small Marshmallows of 4 different colors
Large White marshmallows
Small White marshmallows
Toothpicks
Directions
Use your knowledge of how the base pairs of DNA bond to create an accurate model of a DNA code that is handed to you at the start of the lab
Use the colored marshmallows to represent the different base pairs, the large white marshmallows to represent the sugar, and the small white marshmallows for the phosphate groups. Keep in mind that purines bases are larger than pyrimidine bases!
Record your random 7-digit code here ___________________________________
Use the space below to create a key that will identify the parts of the model, and their corresponding parts in DNA
Follow-up Questions
1. What is the sugar that makes up DNA?
2. How does the number of adenines compare to the number of thymines? How about cytosines to guanines? Provide sample numbers.
3. How do the number of purines compare to the number of pyrimidines? Provide sample numbers.

21. DNA Extraction Lab