Do Now: Do Now: 1. What structure makes proteins? 2. Where are these found? 3. Where is DNA stored? 4. Why not in cytoplasm? Homework: read 12-3 and complete packet

DNA is safe inside the nucleus, but ribosome are in the cytoplasm!!

RNA is a “messenger molecule” that can take the code into the cytoplasm.

Trait

Overview of Protein Synthesis Transcription Translation

Ribonucleic acid Responsible for the movement of genetic information from the DNA in the nucleus to the site of protein synthesis in the cytosol 1. RNA

A. Structure of RNA: –Single-stranded Nucleic acid made up of repeating units, like DNA –Sugar molecule is RIBOSE (not deoxyribose) –Thymine is replaced with URACIL (U)

1.Messenger RNA (mRNA) a. STRUCTURE= RNA nucleotides in a single uncoiled chain b. FUNCTION= Carries genetic info from the nucleus to the ribosome

2.Transfer RNA (tRNA) a. STRUCTURE= RNA nucleotides in a single chain folded into a cloverleaf shape b. FUNCTION= binds to specific amino acids and helps form polypeptide chains

3. Ribosomal RNA (rRNA) a. STRUCTURE = RNA nucleotides in a globular form b. FUNCTION = makes up the ribosomes where proteins are made

The production of proteins The amount and kind of proteins produced in a cell determine the structure and function of the cell Protein’s carry out the genetic instructions encoded in an organism’s DNA

Proteins are POLYMERS Made up of amino acids There are 20 different amino acids that make up proteins

a. Transcription *STEP 1 of PROTEIN SYNTHESIS*

What is it??? –making mRNA from DNA NOTE: –Transcribe = to copy T r a n s c r i p t i o n

1.RNA polymerase binds to DNA at the promoter and separates the DNA strands. 2.RNA polymerase then uses one strand of DNA as a template. Using the template as a guide, nucleotides are assembled into a strand of mRNA. T r a n s c r i p t i o n Steps

DO NOW: Transcription 1. Where does Transcription occur? 2. What is produced at the end of transcription? 3. What enzyme is used in transcription?

b. T r a n s l a t i o n *STEP 2 of PROTEIN SYNTHESIS*

The process TRANSLATING the message encoded in mRNA to assemble a protein. Begins when mRNA leaves the nucleus through pores in the nuclear membrane The mRNA then migrates to a ribosome in the cytosol, the site of protein synthesis T r a n s l a t i o n

THE GENETIC CODE The genetic information necessary for making proteins is encoded in series of three mRNA nucleotides Each combination of 3-mRNA nucleotides is called a CODON Each codon codes for a specific amino acid

tRNA carries the “Anticodon”... Allows tRNA to match up with mRNA codon Codons in mRNA

**Start codon=AUG** If the mRNA sequence is A-A-U (codon) then the tRNA sequence is U-U-A (anticodon)

mRNA tRNA rRNA All three types of RNA are involved in Translation

Phase 1: Initiation mRNA leaves nucleus mRNA attaches to a ribosome tRNA attaches to a start codon (AUG)

Phase 2: Elongation tRNA anticodon binds with next mRNA codon adjacent amino acids bond (begin a polypeptide chain) Ribosomal unit shifts down to next codon, first tRNA leaves

Phase 3: Termination Ribosomal unit stops when reaches stop codon All units detach, and polypeptide folds into a protein

1.mRNA arrives at a ribosome 2.mRNA is pulled through the ribosome 3.Start codon (AUG) signals tRNA to start arriving T r a n s l a t i o n Steps

4.One tRNA matches up to the codons on mRNA to deposit an amino acid 5.Another tRNA comes in and adds another amino acid to the chain. 6.Process continues until stop codon is reached and enough amino acids have been linked to form a protein.

T r a n s l a t i o n

Mutations Mutations = errors –Mutations can occur as a “typo” in the sequence of nitrogen bases. –For example if a sequence should be A-C-G, a mutation could occur and it is now A-G-C... What affect could this have on the protein produced?

PROTEIN SYNTHESIS ANIMATION