DNA, RNA and Protein Synthesis

1. DNA, RNA and Protein Synthesis Chapter 11

2. DNA Structure • DNA is a chain of Nucleotides • 3 parts of a Nucleotide: • sugar (deoxyribose) • Phosphate • nitrogen base - 4 possiblebases: • Adenine • Guanine • Thymine • Cytosine

3. Structure of DNA (continued) • The DOUBLE HELIX (looks like a twisted ladder) • Double Stranded– • 2 sugar/ phosphate backbones • rungs = nitrogen base pairs • hydrogen bonds between complementary nitrogen bases • complementary= will bond together • A is complementary to T, • G is complementary to C • Base-pairing rules • A-T • C-G • The number and sequence of the nitrogen bases determines the CODE of the genes in the DNA!

4. DNA Replication • DNA making copies of itself is called DNA REPLICATION (Why might DNA need to copy itself?) • Steps of DNA replication are controlled by enzymes. 2 of the main enzymes are: • Helicase: untwists the DNA • DNA polymerase: adds new nucleotides and connects them to build up a new strand (follows base-pairing rules!) • DNA ReplicationC:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 11 BDOL IC

5. RNA • Structure of RNA • nucleotide • sugar= ribose • phosphate • nitrogen base (instead of thymine, RNA has Uracil). • Uracil is complementary to Adenine (it replaces Thymine) • Single stranded

6. RNA Function of RNA • accomplish protein synthesis • Why?--DNA is trapped in the nucleus but protein synthesis happens at ribosomes located in cytoplasm SO… • Messenger RNA (mRNA) is used to take the message from DNA to the ribosome • Ribosomal RNA (rRNA) attaches to mRNA and helps assemble proteins • Transfer RNA (tRNA) transfers (brings) amino acids to mRNA so that they can be attached to make a protein

7. Compare and Contrast DNA and RNA in the following table

8. Protein Synthesis 11.2 From DNA to PROTEIN • I. The Purpose of DNA: DNA is used to make RNA which is used to make proteins!! • Central Dogma of Molecular Biology-(DNA--> RNA--> Proteins) • A. One DNA molecule has many GENES on it! • B. Gene—segment of DNA molecule that codes for a specific protein.

9. Protein Synthesis Step 1: Transcription • III. TRANSCRIPTION • A. Transcription is the synthesis of mRNA using the code of a gene (DNA) as a template (pattern). • B. Steps • 1. the gene is located and an enzyme unzips DNA and attaches RNA nucleotides following base pairing rules. • This makes a single stranded mRNA • 2. Single stranded mRNA leaves the nucleus and goes to the ribosome. • Transcription Animation C:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 11 BDOL IC

10. Protein Synthesis Step 2: Translation • IV. Translation (Converting the “language” of mRNA to the language of proteins.) • Codon= triplet of nitrogen bases on mRNA • Each codon codes for one specific amino acid • Note: amino acids are the building blocks of proteins • This code is universal- it applies to all organisms!

13. Translation continued… • The order of codons determines the order of amino acids found in the protein. • mRNA from nucleus is ‘read’ along its codons • this occurs at the ribosome • tRNA has anticodons that are complementary to specific codons • Each tRNA can only bind one amino acid • tRNA transfers or transports the amino acids to the ribosome where they are attached (in order) to make a polypeptide chain. • Translation Animation ..\..\bio powerpoints\Chapter 11 BDOL IC\GB4F605M.AVI • Analogy of Transcription through translation (RNAi explained) • http://www.pbs.org/wgbh/nova/sciencenow/3210/02.html