Ch. 9 &10 DNA, RNA & Protein Synthesis

I. DNA-Deoxyribonucleic Acid A. In 1953 James Watson and Francis Crick built a model of DNA based on x-rays taken by Rosalind Franklin

B. DNA Structure 1. Shape- Double Helix (winding staircase) 2. Made of Repeating Nucleotides: 3 parts a) Phosphate group b) Deoxyribose Sugar c) Nitrogen base

C. Nitrogen Bases- 2 types 1. Purines- 2 carbon rings in structure, Adenine & Guanine 2. Pyrimidines- 1 carbon ring in structure, Thymine & Cytosine

D. A Purine is always paired with a pyrimidine, held together by weak H bonds A=T G C 2 stars3 stars E. Bases are always attached to deoxyribose sugars

PSPSPS DNA drawing -A -C -G -C -G -T = = == = = Right-hand rule= nitrogen bases only bond on R side- results in 2 opposite running strands PSPSPS n_how_he_discovered_dna.html

QUIZ 1. Name the people who made the first model of DNA. 2. What are the 4 nitrogen bases (words not letters)? 3. What are the three parts that make up a nucleotide? 4. What is DNA’s shape? 5. Which bases are pyrimidines? 6. Which are doubled-ringed, purines or pyrimidines? 7. What type of bonds hold the nitrogen bases together in the middle of the DNA strand? 8. How many bonds form between A and T? 9. How many bonds form between G and C? 10. Why is a DNA molecule said to be complementary? 11. What is the complementary strand of DNA for ACATGG?

Answers-18 pts total 1. 2-Watson and Crick 2. 4-Adenine, Guanine, Cytosine, Thymine 3. 3-Phosphate, Sugar, Base 4. 1-Double helix/winding staircase 5. 2-Thymine, cytosine 6. 1-Purines Hydrogen Bonds hydrogen bonds hydrogen bonds by knowing the nitrogen bases on one side of the DNA we can determine the sequence of bases for the other side of the DNA TGTACC

II. DNA Replication A. Replication- the process of copying DNA to get ready for cell division, occurs in the nucleus B. Steps 1. Helix unwinds and an enzyme (DNA helicase) breaks the Hydrogen bonds between the bases

2. Enzyme (DNA Polymerase) moves along each strand and adds the complementary base to each ½ strand; Polymerase also proofreads its work

3. Strands Detach and 2 new identical strands are formed

4. Process is considered a semi-conservative process because the strands are ½ original, ½ new DNA

III. Protein Synthesis A. The process of producing proteins made of amino acids from the instructions provided by the DNA

B. RNA-(ribonucleic Acid) gets instructions to ribosome to make proteins 1. Single Strand 2. Ribose instead of Deoxyribose Sugar 3. No Thymine, Uracil replaces Thymine 4. 3 Types of RNA

a) Messenger RNA- (mRNA)- copy of information from DNA - every 3 nitrogen bases make a codon, these code for a specific amino acid

b)Transfer RNA- (tRNA)- transports amino acids, has a matching anti-codon -3 nitrogen bases make an anticodon

c) Ribosomal RNA- (rRNA)- makes up ribosomes

C. Transcription-unwinds DNA and makes a copy called mRNA, occurs in the nucleus ***2 steps for Protein Synthesis

D. Translation- mRNA and tRNA build a protein out of amino acids. Occurs in the cytoplasm at a ribosome

Animations imat/molgenetics/dna-rna2.swf imat/molgenetics/dna-rna2.swf imat/molgenetics/dna-rna2.swf imat/molgenetics/dna-rna2.swf imat/molgenetics/transcription.swf imat/molgenetics/transcription.swf imat/molgenetics/transcription.swf imat/molgenetics/transcription.swf at/molgenetics/translation.swf

IV. Mutations- a change in the DNA of a gene, occurs during replication 3 types: 1. Substitution- one nucleotide is replaced with a different nucleotide 2. Insertion- one or more nucleotides are added 3. Deletion- one or more nucleotides are deleted

Humans inherit 3 billion base pairs of DNA from each parent. That means that each cell has 6 billion pairs that can be a target of a mutation. It is estimated that mutations occur in about 1 in every 50 million nucleotides. That means that each new cell could have some 120 mutations Mutations can: -have no effect (occur in the “junk DNA”, about 97% of DNA does not encode for anything- that we know of) -be silent-mutations that code for the same amino acid -cause disease such as Cystic Fibrosis, Retinoblastoma, Sickle Cell anemia -occur in gametes (egg & sperm)- can result in Fragile X syndrome and Huntington’s disease