NOTES: Chapter 13 - RNA & Protein Synthesis Vocabulary: Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA) Transcription RNA Polymerase Codon Translation Anticodon Key Concepts: What are the 3 main types of RNA? What is transcription? What is translation?

Genes and Proteins: RECALL: the sequences of nucleotides in DNA contain INFORMATION! This information is put to work through the production of PROTEINS.

What do proteins do for the body? Proteins are diverse:  control chemical messages in cell;  direct the synthesis of carbo’s, lipids, and nucleotides;  enzymes;  give the cell structure and movement Goal of protein synthesis: MAKE A PROTEIN

Protein Structure: RECALL: proteins are polymers of AMINO ACIDS The sequence of nucleotides in each GENE contains the information for the sequence of AMINO ACIDS in a single protein Each human cell contains about +/- 35,000 genes

RNA Like DNA= made of nucleotides copy of DNA segment 3 main types: mRNA, rRNA, tRNA 3 differences 1) sugar = ribose 2) single stranded 3) instead of the base thymine (T), RNA uses URACIL (U)

Job of RNA: Function in Protein Synthesis

Role of RNA – an analogy Imagine what goes into a new car being built on an automobile assembly line: Engineers make the design and tell the workers how to make the cars; Workers follow the directions to build the cars; Suppliers bring parts to the assembly line so they can be installed in the car

Role of RNA – an analogy Now imagine what goes into PROTEIN SYNTHESIS: DNA provides the “workers” with the instructions for making proteins; The workers (RNA molecules!) follow the instructions from DNA and build the proteins; Other workers (other RNA molecules) bring parts (AMINO ACIDS) over to the assembly line

3 Types of RNA: Messenger RNA (mRNA): brings information from the DNA in the nucleus out to the ribosomes; Ribosomal RNA (rRNA): clamp on to the mRNA and use its information to assemble amino acids into a protein; Transfer RNA (tRNA): the “supplier”; transports amino acids to the ribosome

DNA  RNA How does the information in DNA , which is found in the nucleus, get out to the ribosomes in the cytoplasm…it needs a “MESSENGER”!

Transcription Transcribe: to make a copy Step #1 (of 2) of protein synthesis Transcribe: to make a copy transcribing DNA information (gene instructions) into mRNA mRNA can leave the nucleus  ribosomes in the cytoplasm special base sequences in DNA are recognized by RNA as “start” and “stop” signals “Start” sequence called PROMOTER region of DNA

Details of the Process 1. RNA polymerase attaches to DNA at the site where instructions for the needed protein begins & it separates the 2 DNA strands

2. RNA polymerase synthesizes the mRNA strand using complementary base-pairing

Remember…there aren’t “T” bases in RNA “C” binds with “G” DNA “A” binds with RNA “U”

Which strand was copied? A or B

3. when RNA polymerase reaches the end or "STOP" part of the genetic code for that protein, it releases 4. DNA re-zips  5. finished mRNA (message) leaves the nucleus and goes to a ribosome in the cytoplasm

Bases are grouped by 3 Called a CODON (“code”)

Transcription Translation

Transcription ends with mRNA which will exit the nucleus to the cytoplasm So… if transcription is the first step of Protein Synthesis, what happens next in the cytoplasm?

TRANSLATION Making a protein (string of amino acids): translating from the language of nucleic acids into a polypeptide How does it go from mRNA (copy of DNA) to amino acids (building blocks of proteins)?  A group of 3 mRNA bases makes up a “codon” (think of as a “code word”)  each codon specifies a particular amino acid  there are “start” and “stop” codons

The Mechanism... 1) mRNA attaches onto the ribosome  3 nucleotides of mRNA = codon 2nd kind of RNA= ribosomal RNA (rRNA)  makes up the majority of the ribosome

The Mechanism continued... 3rd kind of RNA= transfer RNA (tRNA)  carries amino acids to the ribosomes (amino acids join together)  3 nucleotides of tRNA that “match” or complement the mRNA = anticodon  there are 64 different tRNA molecules (more than 1 for each amino acid)  REDUNDANCY of the CODE!!

tRNA Amino acid tRNA anticodon mRNA codon

amino acid tRNA anticodon codon (mRNA)

The Mechanism continued... 2) By matching the codon of mRNA to the anticodon of tRNA, the correct amino acid is put into place Next tRNA goes here!!!!

The Mechanism continued... 3) a peptide bond is formed between the 2 amino acids

The Mechanism continued... 4) protein chain continues to grow until a “stop” codon is reached on the mRNA  no tRNA exists for “stop” codons

tRNA anticodon mRNA codon Amino acid ·  Molecules of tRNA are specific for only 1 amino acid -one end of tRNA attaches to a specific amino acid -the other end attaches to mRNA codon by base pairing (anticodon = a sequence of 3 bases on tRNA) tRNA anticodon mRNA codon

● tRNA’s decode the genetic message codon by codon

This table shows the “dictionary” for the codons and their corresponding amino acids

Transcription Translation

Translation: All At Once

PROTEIN SYNTHESIS: All At Once

PROTEIN SYNTHESIS DNA Step 1. TRANSCIPTION (nucleus) mRNA Step 2. TRANSLATION (ribosome) tRNA PROTEIN

Protein Synthesis: the whole process

Protein Synthesis—video http://www.sciencenetlinks.com/interactives/protein.html

PRACTICE: DNA: T A C C G C G G T T T A A C T RNA: amino acids:

PRACTICE: DNA: T A C C G C G G T T T A A C T RNA: A U G G C G C C A A A U U G A amino acids:

PRACTICE: DNA: T A C C G C G G T T T A A C T RNA: A U G G C G C C A A A U U G A amino acids: met – ala - pro - asn - STOP