Nucleic Acids Protein Synthesis Chapter 10 1 Structure

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

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

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

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

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

Evidence of the Double Helix l Rosalind Franklin and Maurice Wilkins had X-ray photographs of DNA crystals l 1962 - Watson, Crick, & Maurice received the Nobel Prize in Medicine for their work on DNA l Rosalind died in 1958 and was never acknowledged

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

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

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

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

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

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