You have been given a mission:  You must crack the code that you have been given. How many letters does it look like it requires to make just one English Letter?  What information did you use to crack the code?

Protein Synthesis -The process of making a protein from a gene

What is a gene?  A gene is a specific section of DNA along the length of a chromosome.  It has a beginning (the “promoter”) and an end (the “termination signal”).  A gene holds the instructions for making a specific protein.

Codes for insulin Codes for a hormone receptor

The path from DNA to protein 1.) DNA 2.) Process of Transcription 3.) RNA 4.) Process of Translation 5.) Protein

DNA vs. RNA  Similarities Nucleic acids Made of nucleotides with a sugar, nitrogen base, and phosphate groups  Differences RNA has ribose sugar (instead of deoxyribose) RNA has uracil instead (U) of thymine (T) RNA is single-stranded

Base-pairing between DNA & RNA during transcription

Videos:  ayer.asp?mediaID=12495&segmentI D= ayer.asp?mediaID=12495&segmentI D=20846

Types of RNA -messenger RNA -transfer RNA -ribosomal RNA

Messenger RNA (mRNA)  Location: nucleus & cytoplasm  Structure: single, unfolded chain of nucleotides. Contains a series of codons. 3 bases = codon = code for an amino acid  Function: to carry the instructions for making the protein from inside the nucleus to the ribosomes.

Transfer RNA (tRNA)  Location: cytoplasm  Structure: single chain folded into “cloverleaf” shape. Has an anticodon on one end and binds an amino acid on the opposite end.  Function: to transfer (deliver) the correct amino acids to the ribosome. There are many different tRNAs; each carries a different a.a.

Ribosomal RNA (rRNA)  Location: cytoplasm (“free” or on the rough ER)  Structure: rRNA, combined with proteins. Has two subunits.  Function: coordinates the building of a protein. Binds mRNA and tRNA; catalyzes peptide bond formation.

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Transcription & Translation  Warm Up:  1. What are the building blocks (monomer) of a protein?  2. What acts as a messenger between DNA & ribosomes?  3. Define a codon.

Transcription: Gene to message  Creating the “messenger”  Making a strand of mRNA using DNA as a template. mRNA = copy of gene  Allows for transfer of info from DNA to site of protein synthesis (cytoplasm)

Transcription  DNA contains the instructions for making protein but cannot leave the nucleus  Proteins are made by the ribosomes, which are found outside the nucleus  Somehow the info held by the DNA must make it’s way outside the nucleus to the ribosome, done by creating the “messenger”

Steps of Transcription: 1.The enzyme RNA polymerase binds to a promoter on specific gene in DNA 2.DNA molecule in that region “unzips” 3.RNA nucleotides are paired to complementary bases on the DNA template strand  Complementary base-pairing: C-G, G-C, T-A, A-U

Transcription, cont’d… 5.mRNA strand lengthens until RNA polymerase reaches a “termination signal” 6.Single stranded mRNA strand is made & seperates from the DNA template.  DNA re-twists into double-helix.

mRNA Carries Message from Nucleus to Cytoplasm /educational/medicin e/dna/b/transcriptio n/transcription_ani.h tml omain.org/resource/ls ps07.sci.life.stru.celltr ans/

Problem Solving  If you know the DNA sequence, you can determine the mRNA sequence

More Practice  Use the DNA sequence below to determine the mRNA sequence: DNA: T-A-C-G-A-T-A-T-C mRNA: A-U-G-C-U-A-U-A-G

Translation  Making a protein using an mRNA template. mRNA = copy of gene Every 3 letters on mRNA = codon = codes for a specific amino acid (a.a.).  e.g.: the codon AUG codes for methionine (“met”)known as the “start” codon. Amino acids will be bonded together in a specific sequence. Correct a.a. sequence is critical to the protein being functional (having the right shape).

mRNA-tRNA connection  mRNA contains the “codes” for the amino acids.  tRNA delivers the amino acids.  tRNA brings the right a.a. to the right place in the protein by binding to the mRNA. Codon and anticodon are complementary.

The “Genetic Code”  The a.a. brought by tRNA is specified by the mRNA codon, NOT the anticodon.

mRNA, tRNA, and a ribosome work together in constructing a protein  mRNA = “messenger”; it contains the message that is being translated.  tRNA = “transfer”; it transfers (delivers) the right a.a. to the right codon. It is the “interpreter”. When you translate an mRNA sequence, you are the “interpreter”. You determine the correct a.a. for each codon by looking at the Genetic Code table.  rRNA = “ribosomal”; as part of the structure of the ribosome, it helps bond amino acids together.

Steps of Translation 1.mRNA attaches to a ribosome in the cytoplasm. 2.A tRNA, carrying the amino acid “met”, binds to the start codon (AUG) on mRNA. A second tRNA w/an a.a. binds to the ribosome. 3.A peptide bond is formed between the a.a.

Translation, cont’d 4.The process of a.a. delivery by tRNA and peptide bond formation continues until the chain is 100+ amino acids long. 5.When a stop codon is reached, translation ends and the polypeptide (protein) is released. 6.The polypeptide’s a.a. sequence will determine how the protein folds into a 3-D functional shape.

Finish your “steps in Protein Synthesis” and answer the following questions on the back.  What is the end result of Translation?  What RNA codon or anticodon will you use to find the amino acid?  What chart will you use to find the amino acid?

The amino acid “Tyr” is carried by a tRNA, but it is coded for by the mRNA codon (UAC)