1 NOTES: Chapter 13 - RNA & Protein Synthesis Vocabulary: Messenger RNA (mRNA) Ribosomal RNA (rRNA)...
Transcript of 1 NOTES: Chapter 13 - RNA & Protein Synthesis Vocabulary: Messenger RNA (mRNA) Ribosomal RNA (rRNA)...
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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?
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Genes and Proteins:• RECALL: the sequences
of nucleotides in DNA contain INFORMATION!
• This information is put to work through the production of PROTEINS.
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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
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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
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• Like DNA= made of nucleotides• copy of DNA segment• 3 main types: mRNA, rRNA, tRNA• 3 differences
1) sugar = ribose2) single stranded
3) instead of the base thymine (T), RNA uses URACIL (U)
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Job of RNA: Function in Protein Synthesis
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Role of RNA – an analogy
• Imagine what goes into a new car being built on an automobile assembly line:
1) Engineers make the design and tell the workers how to make the cars;
2) Workers follow the directions to build the cars;
3) Suppliers bring parts to the assembly line so they can be installed in the car
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Role of RNA – an analogy
• Now imagine what goes into PROTEIN SYNTHESIS:
1) DNA provides the “workers” with the instructions for making proteins;
2) The workers (RNA molecules!) follow the instructions from DNA and build the proteins;
3) Other workers (other RNA molecules) bring parts (AMINO ACIDS) over to the assembly line
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3 Types of RNA:
1) Messenger RNA (mRNA): brings information from the DNA in the nucleus out to the ribosomes;
2) Ribosomal RNA (rRNA): clamp on to the mRNA and use its information to assemble amino acids into a protein;
3) Transfer RNA (tRNA): the “supplier”; transports amino acids to the ribosome
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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”!
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• 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
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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
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2. RNA polymerase synthesizes the mRNA strand using complementary base-pairing
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• Remember…there aren’t “T” bases in RNA
• “C” binds with “G”• DNA “A” binds with RNA “U”
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Which strand was copied? A or B
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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
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• Bases are grouped by 3• Called a CODON (“code”)
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• 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?
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• 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
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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
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• 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!!
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Amino acid
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amino acid
tRNA
anticodon
codon (mRNA)
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2) By matching the codon of mRNA to the anticodon of tRNA, the correct amino acid is put into place
Next tRNA goes here!!!!
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3) a peptide bond is formed between the 2 amino acids
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4) protein chain continues to grow until a “stop” codon is reached on the mRNA
no tRNA exists for “stop” codons
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· 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)
Amino acid
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● tRNA’s decode the genetic message codon by codon
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This table shows the “dictionary” for the codons and their corresponding amino acids
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Translation: All At Once
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PROTEIN SYNTHESIS: All At Once
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PROTEIN SYNTHESIS
Step 1. TRANSCIPTION(nucleus)
Step 2. TRANSLATION(ribosome)
DNA
mRNA
tRNA
PROTEIN
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Protein Synthesis—video
http://www.sciencenetlinks.com/interactives/protein.html
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PRACTICE:
DNA: T A C C G C G G T T T A A C T
RNA:
amino
acids:
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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:
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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