DNA: Deoxyribonucleic Acid Q2 WK6 D1 11/18/13

Scientists of DNA 1953, James Watson & Francis Crick were accredited for discovering the structure of DNA Awarded the Nobel Prize for Physiology and Medicine in 1962; Watson, Crick and Maurice Wilkins

Scientists of DNA Rosalind Franklin: Rosalind refined the technique of X-ray crystallography, to study DNA and produced “Photo 51” From photo 51, Rosalind determined that DNA is the shape of double helix Watson & Crick used photo 51 and published their results before Franklin Rosalind Franklin died in 1985

Location of DNA DNA is coiled in chromosomes; chromosomes are located in the nucleus. DNA is the shape of double helix Double stranded Twisted Similar to a spiral staircase

Double Helix looks like… If a DNA strand was straightened, what would it look like???

Make up of DNA DNA is made up of Nucleotides strung together in a certain order. Each nucleotide contains… Deoxyribose (Sugar) Phosphate Nitrogen base Adenine (A) Thymine (T) Guanine (G) Cytosine (C)

How is DNA organized? Sugar alternates with phosphate at the sides The rungs (steps) of the DNA molecule are paired nitrogen bases The nitrogen bases pair in the following way… Adenine ALWAYS pairs with Thymine (A-T) Cytosine ALWAYS pairs with Guanine (C-G)  The rungs are connected at the sugars

Nitrogen Base: PRACTICE 1.Adenine - 2.Cytosine - 3.Thymine - 4.Adenine - 5.Guanine - 6.Guanine - 7.Cytosine - 8.Thymine - Add to notebook check Write the appropriate pair with the listed nitrogen base…

Nitrogen Base: answers Thymine Guanine Adenine Thymine Cytosine Guanine Adenine 1.Adenine 2.Cytosine 3.Thymine 4.Adenine 5.Guanine 6.Guanine 7.Cytosine 8.Thymine

DNA structure: REVIEW DNA shape = double helix Rails = Phosphate & deoxyribose (sugar) alternate Rungs= Nitrogen base pairs Base Pairing Rule: Adenine – Thymine Guanine – Cytosine Purines: Adenine & Guanine; made of 2 carbon rings and nitrogen atoms. Pyrimidines: Thymine & Cytosine; made of a single ring of carbon and nitrogen atoms

Q2 WK7 D1

Purines & Pyrimidines

DNA Replication During the cell cycle DNA replication occurs the “S” (synthesis) phase DNA Replication: The process of making a copy of DNA DNA replication results in 2 identical DNA strands DNA is copied BEFORE the cell divides

Steps of DNA Replication Step 1: Before DNA can replicate, the double helix unwinds. An enzyme called “ DNA Helicase” breaks the bonds between the nitrogen bases. Once the strands separate, proteins prevent the strands from making their double helix shape. Areas where the double helix separates are called “Replication forks”.

DNA unwinds DNA Helicase- Enzyme that opens the double helix Replication fork- areas where the DNA opens

Tuesday 12/1/2015 Agenda: DNA  Notes: DNA Replication (Steps 2 and 3)  Activity: DNA Replication Worksheet  Homework :  DNA Replication Worksheet due Wednesday/Thursday 12/2-12/3/2015 for 15 Points  GRADEBOOK CLOSES FRIDAY 12/11/2015!!! DNA Structure and Replication Quiz Friday 12/4/2015!!

Steps of DNA Replication Step 1: Before DNA can replicate, the double helix unwinds. An enzyme called “ DNA Helicase” breaks the bonds between the nitrogen bases. Once the strands separate, proteins prevent the strands from making their double helix shape. Areas where the double helix separates are called “Replication forks”.

DNA unwinds DNA Helicase- Enzyme that opens the double helix Replication fork- areas where the DNA opens

Steps of DNA Replication Step 2: At the replication fork, an enzyme known as “DNA polymerase” moves along each of the DNA strands. DNA polymerase starts adding nucleotides to the exposed nitrogen bases; using the base pairing rules. End result: 2 new double helices are formed.

DNA polymerase: An enzyme adding nucleotides to the EXPOSED bases; forming 2 identical copies of DNA

Steps of DNA Replication Step 3: Once DNA polymerase adds nucleotides to the exposed bases, it continues until the polymerase is signaled to detach. The 2 new double helices are made up of an old and NEW strand DNA sequence is identical to each other and to the original DNA molecule

End result: 2 identical DNA molecules Each made up of an OLD and NEW strand