DNA Chapter

I. Time Frame and History of DNA Friedrich Meisher Recognized DNA as a chemical in the nucleus 1868

I. Time Frame and History of DNA Fredrick Griffith 1928 p.577

I. Time Frame and History of DNA Oswald Avery 1944 p.578

Time Frame and History of DNA Alfred Hershey & Martha Chase 1952 p.579

I. Time Frame and History of DNA Erwin Chargaff 1950 Chargaff’s Rules A = T G = C p.587

I. Time Frame and History of DNA R. Franklin & M. Wilkins Early

X-Ray Crystallography Anatomy of Photo 51 NOVA photograph.html

I. Time Frame and History of DNA James Watson & Francis Crick 1953

I. Time Frame and History of DNA The Original DNA Model

II. The Structure of DNA A. Nucleotide

The Nitrogen Bases  There are four: 1. Adenine 2. Thymine 3. Guanine 4. Cytosine Purines (2 rings) Pyrimidines (1 ring)

II. The Structure of DNA C. Base Pairing 1. 1 purine + 1 pyrimidine 2. T=A G=C 3. Only the sequence varies from organism to organism

III. DNA Replication A. Template Mechanism model

DNA Replication  Semi-conservative nature

IV. Protein Synthesis A. Protein Synthesis Overview 1. Genes make proteins 2. Ribosomes 3. RNA

DNA vs. RNA CharacteristicDNARNA StructureDouble strand Single strand PurinesAdenine (A) Guanine (G) Adenine (A) Guanine (G) PyrimidinesCytosine (C) Thymine (T) Cytosine (C) Uracil (U) SugarDeoxyriboseRibose

Protein Synthesis C. Types of RNA 1. Messenger RNA(mRNA) 2. Transfer RNA (tRNA) 3. Ribosomal RNA (rRNA)

Protein Synthesis transcription translation DNA  RNA  Protein

Transcription 1. DNA unwinds and splits. 2. Half of the helix. 3. RNA polymerase assembles mRNA nucleotides. 4. Parts of the mRNA are needed others are not. a) introns b) exons

Transcription

Transcription Example What mRNA sequence would be made from this DNA template? A-G-C-T-T-A-A-C-G-T-A-G-C

Translation 1. mRNA 2. Ribosome 3. tRNA 4. Amino acids are assembled 5. Start codons/stop codons

@ the ribosome…

Translation

Can you transcribe this DNA template to an mRNA strand? T-A-C-G-T-A-A-A-A-C-G-A-C-T-A-A-T-T

Protein Synthesis Here’s the answer: T-A-C-G-T-A-A-A-A-C-G-A-C-T-A-A-T-T A-U-G-C-A-U-U-U-U-G-C-U-G-A-U-U-A-A Now, translate this into an amino acid sequence!

Translation

Protein Synthesis The answer is: A-U-G-C-A-U-U-U-U-G-C-U-G-A-U-U-A-A Met His Phe Ala Asp STOP Protein synthesis is complete

V. Mutations Mutations 1. any change in a nucleotide sequence. 2. Substitutions - match the incorrect base in a sequence. -sometimes does not affect organism. WHY???? (these are called silent mutations)

Mutations 3. Insertions a. Extra bases are added to a sequence. b. can affect an entire strand of codons. 4. Deletions a. Bases are left out of a sequence. b. Can also affect entire strands.

Mutations 5. Examples: Original Strand: ATTCGCGTATAA a. Substitution: ATTCGAGTATAA b. Insertion: ATTGCGCGTATAA c. Deletion: ATCGCGTATAA How do these affect the proteins that are made?

Mutations B. Mutagens 1. cause mutations 2. physical or chemical agents 3. ex: radiation, x-rays, carcinogens 4. Most mutations are harmful, some can be helpful! 5. If the mutation happens in the gametes, or is in the gametes, it can be passed to offspring.