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Slide 1 of 39
Copyright Pearson Prentice Hall
12-3 RNA and Protein Synthesis12–3 RNA and Protein Synthesis
12–3 RNA and Protein Synthesis
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Copyright Pearson Prentice Hall
12–3 RNA and Protein Synthesis
DNA is located in the nucleus.
DNA is impermeable to the nuclear envelope.
Genes are segments of DNA which code for the production of proteins.
Ribosomes outside the nucleus make the proteins.
RNA contains coded information for making proteins.
12–3 RNA and Protein Synthesis
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Do you see a problem with this scenario?
12–3 RNA and Protein Synthesis
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RNA is the solution to this problem.
RNA is DNA’s main man.RNA is DNA’s “go to guy”.RNA is DNA’s number one
“get it done person”.
One of RNA’s jobs is to copy DNA’s instructions and take those instructions
out of the nucleus to the ribosomes.
12–3 RNA and Protein Synthesis
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The Structure of RNA
The Structure of RNA
1. RNA is a type of nucleic acid which is made up of a long chain of nucleotides.
2. Each nucleotide, like DNA, is made up of a:
1. 5-carbon sugar,
2. phosphate group
3. nitrogenous base.
(Sounds familiar..........just like DNA’s nucleotides)
12–3 RNA and Protein Synthesis
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The Structure of RNA
There are three main differences between RNA and DNA:
• 1. The sugar in RNA is ribose instead of deoxyribose.
• 2. RNA is a single-strand of nucleotides.
• 3. RNA contains uracil in place of thymine.
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Types of RNA
There are three types of RNA•1. messenger RNA ~ mRNA
•2. ribosomal RNA ~ rRNA
•3. transfer RNA ~ tRNA
12–3 RNA and Protein Synthesis
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Types of RNA
Messenger RNA (mRNA) copies DNA’s code for making proteins and takes it’s copy to the ribosomes.
12–3 RNA and Protein Synthesis
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Types of RNA
Ribosomal RNA (rRNA) is the main component of a ribosome. rRNA is bound into two “round” units by proteins to form the large and small subunits which make up a ribosome.
Ribosome
Ribosomal RNA
12–3 RNA and Protein Synthesis
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Types of RNA
Transfer RNA (tRNA) transfers specific amino acids to the ribosome for the making of the proteins.
Amino acid
Transfer RNA
12–3 RNA and Protein Synthesis
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Transcription
What is transcription?
12–3 RNA and Protein Synthesis
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Transcription
Transcription
RNA copies DNA’s code in its own language and take the code to the ribosomes to make proteins.
Transcription requires the enzyme RNA polymerase.
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1.During transcription, RNA polymerase attaches to DNA and separates the DNA strands.
Steps to Transcription:
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2. RNA polymerase then adds RNA nucleotides to one side of the DNA molecule/the sense side of DNA.
-DNA is a double strand of nucleotides BUT only one side of the DNA molecule actually codes for making proteins.
12–3 RNA and Protein Synthesis
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2 strands of DNA
1. Sense side:Has code for makingproteins.
2. Antisense side:Has no code~ makes
no sense.
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3. RNA nucleotides are added to the sense side of DNA following the base pair rule:
Guinine bonds to Cytosine and
Uracil bonds to Adenine
A T G G C
GCA CT
Sense side of DNA
U A C C G
12–3 RNA and Protein Synthesis
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4. This single strand of RNA is now known as messenger RNA or mRNA and it now has a copy of DNA’s code for making proteins.
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5. Since mRNA is single stranded it can now take a copy of DNA’s code out of the nucleus to the ribosomes.
12–3 RNA and Protein Synthesis
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Transcription
RNA
RNA polymerase
DNA
Hyperlink
12–3 RNA and Protein Synthesis
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The Genetic Code
Protein Synthesis:
The process of using mRNA’s copy of DNA’s code to make all necessary proteins.
Takes place where?
-at the ribosomes
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Proteins are made up of:-long chains of amino acids
Total number of different amino acids that make up all proteins:
-20
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These 20 different amino acids bond in various orders (like the letters of the alphabet) to create all proteins.
12–3 RNA and Protein Synthesis
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The Genetic Code
A codon consists of three RNA nucleotides in a row on mRNA that code for a particular amino acid.
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Start codon:Three nitrogen bases in a row on mRNA
that starts EVERY protein…..AUG
Amino acid Methionine starts every
protein
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Stop codon:Three nitrogen bases in a row on mRNA
that ends every protein.Three different codons: UAA, UAG, UGA
Stop codon do not code for any amino acid
12–3 RNA and Protein Synthesis
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Translation
What is translation?
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Translation
Translation:
-Process by which the ribosome reads mRNA’s code and makes a protein.
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Translation
Steps of translation:
1. mRNA leaves the nucleus and take its code to the ribosomes.
Nucleus
mRNA
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2. Ribosome attaches to mRNA and moves along it looking for a start codon/AUG.
3. Transfer RNA/tRNA travels through the cytoplasm locating the appropriate amino acid.
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Anticodon:anti =
opposite
An anticodon is three nitrogen bases on the end of tRNA .
Its code is opposite of mRNA’s codon.
12–3 RNA and Protein Synthesis
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Translation
LysinetRNAPhenylalanine
Methionine
Ribosome
mRNAStart codon
4. As the ribosome reads one codon at a time, tRNA brings down the appropriate amino acid.
12–3 RNA and Protein Synthesis
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Translation
5. Amino acids bind together with peptide bonds forming a long chain.
tRNA
Ribosome
mRNA
Lysine
Translation direction
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Translation
6. After a tRNA delivers its amino acid, it breaks away and goes out to find a new amino acid.
7. The process continues until the ribosome reads a stop codon.
Polypeptide
Ribosome
tRNA
mRNA
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8. The long chain of amino acids-now a polypeptide/protein-breaks away and goes where?
-to the golgi-Why to the golgi?
-to be processes and to be given its 3-D shape
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The sequence of bases in DNA is used as a template for mRNA.
The codons of mRNA specify the sequence of amino acids in a protein.
CodonCodon Codon
Codon Codon Codon
mRNA
Alanine Arginine Leucine
Amino acids within a polypeptide
Single strand of DNA
Review:
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Hyperlink of translation
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Sense Strand of DNA:
CCAGTATACCCGAGTACCCCGCAGGAGCACCAGGAATTCCGCCATACACGCCCATCCCCACTCGAAAAAAAAAA
TATA Box
Poly-a-tail Promoter Region
Termination Region Site where transcription begins
Site where transcription ends. Start of a gene
End of gene
Primary mRNA:
Intron Exon Intron Exon Intron I------------------I------------------------------------------------I------------I-----------------------I-------------------------------------I
AUAUGGGCUCAUGGGGCGUCCUCGUGGUCCUUAAGGCGGUAUGUGCGGGUAGGGGUGAGCUUUUUUUUUU
Start codon Stop codon Start codon Stop codon Tells ribosome to Tells ribosome to
start making protein stop making protein
Mature mRNA:
Exon ExonI-----------------------------------------------I-----------------------I
AUGGGGCGUCCUCGUGGUCCUUAAAUGUGCGGGUAG
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DNA Codon mRNA codon
tRNA anticodon
Amino Acid
AAA UUU AAA PHENYL
GTC
GGA GLYCINE
METH/START
GAT
GUG VALINE
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CHNOPS LABDNA: TAC AGG GCG ATT
mRNA:____________________tRNA:______________________
Amino Acid sequence: ____________________________________Trait: _____________________
AMINO ACID SEQUENCE TRAIT
Methionine-threonine-glycine-tyrosine- Hairless
Methionine- threonine-glycine-glycine Hairy
Methionine- threonine-proline-proline Plump
Methionine- tyrosine-glycine-lysine Skinny
Methionine-serine-arginine Four-eyed
Methionine-serine-tyrosine Two-eyed
Methionine-glycine-arginine-lysine-proline Long nose
Methionine- proline-arginine-lysine-proline Short nose
Methionine-phenylalanine-lysine No freckles
Methionine- phenylalanine-asparagine Freckles
Methionine- glycine-arginine-arginine Blue skin
Methionine- glycine-arginine-phenylalanine Orange skin
Methionine-isoleucine-isoleucine-leucine Male
Methionine-isoleucine-isoleucine-glycine Female
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Processing pre-mRMA into mature mRNA:
Copyright Pearson Prentice Hall
Section 1 C G T A G A T A T A A A A G C T T A C A T G A C A T G A A T T CG C A T C T A T A T T T T C G A A T G T A C T G T A C T T A A G
Section 2T A T C C G A A T T C T A C A A C T G A A T T C C G G T T T G T AA T A G G C T T A A G A T G T T G A C T T A A G G C C A A A C A T Section 3A A A A A A T G T T T T T T A C
1. Cut out sections 1-3 of DNA and tape together in order.
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2. Locate the beginning of the gene on the sense side of DNA (Top line) and underline it.
How?TATA Box
3.Locate the end of the gene on the sense side of DNA and underline it.
How?poly-A-tail
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4. Act like RNA polymerase…..How?
Use your scissors to cut apart the sense and antisense sides of DNA beginning at the end of the TATA and going to the beginning of the poly-A-tail.
Section 1 C G T A G A T A T A A A A G C T T A C A T G A C A T G A A T T C
G C A T C T A T A T
T T T C G A A T G T A C T G T A C T T A A G
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5. Number the DNA nucleotides 1-54 (start at end of TATA and to the beginning of the poly-a-tail.
6. Put in slashes, dividing it into 3’s or codons.
Section 1 C G T A G A T A T A A A A G C T T A C A T G A C A T G A A T T C
G C A T C T A T A T
T T T C G A A T G T A C T G T A C T T A A G
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7. Cut out the two sections of pre-RNA and tape together. Put in slashes, dividing it into 3’s or codons.
8.Complete the process of transcription. How?
You now have just made pre-mRNA
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9. Locate the beginning of a protein.How?
Start codonAUG
10.Locate the end of a protein. How?
Stop codonUAAUAGUGA
11. Locate the next set of start and stop codons.
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12.Label the introns and exons.Introns:
Non codingExons:
Express……codes for a protein
13.Cut out the introns.14.Tape together the exons.15.Add a protective 5’ cap to the front and
a protective poly-A-tail tail to the end. These protect the mature mRNA from harmful enzymes in the cytoplasm.