Presentation on theme: "Discovery and composition"— Presentation transcript:
1 Discovery and composition DNADiscovery 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 miceR (Rough) strain-mice lived
3 Griffith continuedIf Griffith heated the deadly strain before injecting it into the mice, the mice lived.Why??
4 Griffith continuedIf he heated the deadly strain and then mixed it with the harmless strain, the mice died.
5 Transformationthe 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 DNAAvery 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 byRosalind Franklin
8 Watson and Crick1953- 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 unwoundThere is ~1.5 billion miles of DNA in your body3,000 round trips to the moon or 600 round trips to the sunIf 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 groupNitrogenous baseDRAW THIS!!!
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 AT (TA) GC (CG) Purines and Pyrimidines join togetherBase pairing ruleAT (TA)GC (CG)
18 What holds the bases together??? Hydrogen bonds form between nitrogenous basesGuanine is held to Cytosine with a triple bondAdenine is held to Thymine with a double bond
19 Order of basesNucleotides can be joined together in any order (steps of the ladder)This is what makes organisms different from each other!Any sequenceof bases is possible
20 Function of DNA DNA is used to control the cell It tells the cell how to functionDNA holds the instructions for making proteinsProteins are used forAntibodiesEnzymesInsulinReceptor proteinsCytoskeleton
21 Human DNA is 99.9% identical to each other Interesting factsHuman DNA is 99.9% identical to each other99.1% to chimps90% to mice85% to Zebra Fish50% to bananas21% to worms7% 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 QuizThe 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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