Nucleic Acids & Protein Synthesis Chapter 10.1

Structure of DNA Phosphate group Nitrogen-containing base Sugar (deoxyribose)

Three Parts of a DNA Nucleotide Deoxyribose- sugar Phosphate Group- a phosphorus atom surrounded by oxygen atoms Nitrogen-containing base- contains a nitrogen atom

There are 4 nitrogen-containing bases found in DNA nucleotides: Adenine (A), guanine (G), cytosine (C), and thymine (T)

PURINES Bases that have 2 rings of carbon & nitrogen atoms Includes adenine and guanine

PYRIMIDINES bases that have 1 ring of carbon & nitrogen atoms Includes thymine and cytosine

DNA Spiral Staircase Double helix- DNA is composed of 2 nucleotide chains wrapping around each other to form a double spiral Discovered in 1953 by James Watson and Francis Crick

Evidence of the Double Helix Rosalind Franklin and Maurice Wilkins had X-ray photographs of DNA crystals Watson, Crick, & Maurice received the Nobel Prize in Medicine for their work on DNA Rosalind died in 1958 and was never acknowledged

Complementary Base Pairs Cytosine pairs with Guanine Adenine pairs with Thymine Base-pairing rules- describe the pairing behavior of the bases (C-G and A-T) Base pairs are connected by hydrogen bonds

C-G forms three Hydrogen bonds A-T forms two Hydrogen bonds

Replication of DNA Replication- the process of copying the DNA of a cell Two nucleotide chains unwind and each chain acts as a template for a new chain Replication fork- the point at which the 2 chains separate

Helicases- enzymes that separate the chains by breaking Hydrogen bonds DNA polymerases- bind to the separated chains of DNA and help to assemble the new strands

Accuracy and Repair Replication is very accurate (1 error in every 10,000 paired nucleotides) Mutation- a change in the nucleotide sequence at even 1 location Mutations can have serious effects in new cells

Number of errors is reduced as enzymes proofread DNA and repair errors DNA can be damaged by chemicals, pesticides, UV radiation from the sun, etc.