1. Chapter 3- Sec 1 What is DNA?
Life Science

2. DNA What does DNA stand for? Deoxyribonucleic Acid !!!
Deoxyribonucleic Acid, or DNA, is a code that contains information that an organism needs to grow and function.

3. Discovering DNA
In 1952, Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form.
Used X-Rays

4. In 1953, James Watson and Francis Crick created an accurate model of DNA.
Model was similar to a ladder
The structure of DNA is similar to a twisted ladder.
Crick
Thieves?
Watson

5. The structure of DNA is a similar to a twisted ladder (double helix)…

6. DNA Structure
The structure of the “Ladder”…
The sides of the ladder are made up of Deoxyribose (sugar) and Phosphate.
The rungs (or steps) of the ladder are made up of nitrogen bases (ATCG).

7. These bases “fit together” in the combination:
The steps of the ladder are made of pairs of smaller molecules called Nitrogen Bases.
These bases “fit together” in the combination:
Adenine fits with Thymine
Cytosine fits with Guanine
Connected by a Hydrogen bond

8. Joined nucleotides 7
PO4
sugar-phosphate
backbone
+ bases
A molecule of DNA is formed by millions of nucleotides joined together in a long chain

9. What does ATCG stand for???

10. DNA Replication
When a cell divides, the DNA “code” is copied (or duplicated) and passed to the new cells.
The DNA duplicates itself by unwinding and separating the bases forming 2 strands.

13. DNA makes up chromosomes
Each chromosome is composed of a long strand of DNA wrapped around.
Human Body cells have 46 chromosomes or 23 pairs.
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15. How many chromosomes are in other living things?
Toucan – 104
Goldfish – 94
Dogs – 78 chromosomes
Horse- 64
Banana- 22 chromosomes
Jack Jumper Ant- only 2 chromosomes!