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Discovery and composition

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Presentation on theme: "Discovery and composition"— Presentation transcript:

1 Discovery and composition
DNA Discovery and composition

2 Griffith and Transformation
1928 – Frederick Griffith looked at pneumonia bacteria trying to figure out what made people die. S (SMOOTH) strain - killed mice R (Rough) strain -mice lived

3 Griffith continued If Griffith heated the deadly strain before injecting it into the mice, the mice lived. Why??

4 Griffith continued If he heated the deadly strain and then mixed it with the harmless strain, the mice died.

5 Transformation the heat killed bacteria passed their disease-causing ability to the harmless strain. Transformation- one strain of bacteria had been changed permanently into another. A factor was transferred from the heat killed bacteria into the live cells. What was the factor??

6 Avery and DNA Avery experimented to find out which factor in the heat killed bacteria was most important for transformation. DNA stores and transmits genetic information from one generation to the next.

7 Structure of DNA Discovered by James Watson and Francis Crick in 1953
Used x-ray photos taken by Rosalind Franklin

8 Watson and Crick 1953- constructed a model of DNA that was a double helix, two strands were wound around each other.

9 Structure of DNA DNA- Deoxyribonucleic Acid
Composed of 2 long chains of nucleotides

10 Interesting Facts Human DNA contains 3.2 billion base units
About 5 cm unwound There is ~1.5 billion miles of DNA in your body 3,000 round trips to the moon or 600 round trips to the sun If each nucleotide would represent a letter on a text book page, you could stack the pages 65 feet high

11 Components of DNA Nucleotides are made up of 3 components
5-carbon sugar (deoxyribose) Phosphate group Nitrogenous base DRAW THIS!!!

12 DNA

13 Sugar-Phosphate backbone
Sugar and phosphate molecules form the backbone of DNA (sides of the ladder) Nitrogenous bases are attached to the sugar (steps of the ladder)

14 DNA directionality The strands are oriented in opposite directions.
Review! The strands are oriented in opposite directions. This is the only way the bases can line up to form the hydrogen bonds

15 5’  3’ 5’3’ refers to the order of the carbons in the deoxyribose sugar

16 4 types of bases Pyrimidines Cytosine- C Thymine- T Purines Guanine- G
Adenine- A

17 Base-pairing rule Base pairing rule AT (TA) GC (CG)
Purines and Pyrimidines join together Base pairing rule AT (TA) GC (CG)

18 What holds the bases together???
Hydrogen bonds form between nitrogenous bases Guanine is held to Cytosine with a triple bond Adenine is held to Thymine with a double bond

19 Order of bases Nucleotides can be joined together in any order (steps of the ladder) This is what makes organisms different from each other! Any sequence of bases is possible

20 Function of DNA DNA is used to control the cell
It tells the cell how to function DNA holds the instructions for making proteins Proteins are used for Antibodies Enzymes Insulin Receptor proteins Cytoskeleton

21 Human DNA is 99.9% identical to each other
Interesting facts Human DNA is 99.9% identical to each other 99.1% to chimps 90% to mice 85% to Zebra Fish 50% to bananas 21% to worms 7% to bacteria

22 Review Quiz What is the primary function of DNA?
DNA consists of how many chains? What are the subunits called that make up DNA? Name the 3 parts of a nucleotide. DNA bases are made of rings of carbon and ____________. Name the 4 nitrogen bases on DNA. The shape of DNA is known as a ___________ ____________.

23 Review Quiz The sides or backbone of DNA is composed of what 2 things linked together? The center of the helix contains pairs of ___________. What type of bonds hold the bases together? Cytosine pairs with ___________, while adenine pairs with ________. Base pairs that bond to each other are said to be ______________ base pairs. _______ hydrogen bonds join cytosine to guanine, while _______ hydrogen bonds join adenine to thymine.

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