Amoeba Sisters: Why is RNA just as Cool as DNA?

• http://www.youtube.com/watch?v=0Elo-zX1k8M

Protein Synthesis

Transcription and Translation

CENTRAL DOGMA OF BIOLOGY How is information passed?_____ → ______ → ________DNA RNA PROTEIN

Then the protein “DOES SOMETHING”that shows up as a ________trait

The Genetic Code• The sequence of nitrogen

bases along a DNA strand that code for the synthesis of proteins.

• There are 20 different amino acids ( the building blocks of proteins.)

WHAT AREGENETIC TRAITS ?

The same 20 amino acids make up all proteins.

THE 20 AMINO ACIDS: A TYPICAL PROTEIN:

HOW CAN JUST 4 BASES GIVE DIRECTIONS TO MAKE 20 AMINO ACIDS?

Message is read in groups of 3 = _________

UCGCACGGU UCG-CAC-GGU

CODON

Codons represent different amino acids

Serine- Histidine- Glycine

ATG

GCA

DNA mRNAUAC

CGU

triplet codontriplet = 3 nucleotides on a DNA molecule

codon = 3 nucleotides on an mRNA molecule

DNA (triplets)mRNA (codons)

ATT CCT GAG TTCUAA GGA CUC AAG

Each codon codes for a specific amino acid. The sequence ofamino acids determines the type of protein to be made. Remember that amino acids are the monomers of proteins.

All organisms use the same genetic code for amino acids andassembling proteins. That is why the genetic code is said tobe universal.

REMEMBER DNA to RNA A=U !! There is NO THYMINE

Some rules of reading genetic code

The m-RNA CodeSection 12-3

64 possible codons

Some amino acidshave more than onecodon.

START= _______

3 codons for _____

AUG

STOP

Part I: Transcription

• occurs in the nucleustranscription = process where DNA is copied into mRNA

DNA cannot leave the nucleus but the message of DNA needsto get out of the nucleus

mRNA can take message of DNA out of the nucleus

What is the message of DNA?? the order of nucleotides that determine a specific protein

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only

Steps of Transcription1. Helicase unzips DNA helix2. RNA polymerase assembles mRNA

nucleotides but base pairing rules changes slightlya. Thymine in DNA pairs with Adenineb. Adenine in DNA pairs with Uracilc. Cytosine still pairs with Guanine

T - -A - -C - -A - -A - -A - -C - -T - -T - - T - -G - - A - -

DNA

U A C A A A C U U U G A

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Step 1: Helicase enzyme “unzips”

double helix by weakening

H-bonds

Step 2: RNA polymerase

enzyme forms complementary mRNA strand

• Transcription is complete when the mRNA leaves the Nucleus and enters the Cytoplasm.

• The CODONS will then be translated at the ribosome.

The Genetic Code: CODONS code for amino acids

1. UUC

2. CCCProline

Phenylalanine

3. AGCSerine

4. UGAStop

Part II: Translation

• occurs in the ribosomes of the cytoplasm

translation = process where the cell uses information from mRNA to produce proteins

The language of DNA is translated into the language of amino acids

1. The mRNA strand attaches to a ribosome in the cytoplasm2. tRNAs carry specific amino acids to the ribosome3. The tRNA anticodon pairs with the correct mRNA codon4. The ribosome slides along the mRNA to the next codon

while the tRNAs bring more amino acids5. The amino acids are joined together by peptide bonds6. Continues until a STOP codon is reached

Steps of Translation:

Some rules of reading genetic code

mRNAAUG

CGU

codonU

AC

tRNA

Startcodon = 3 nucleotides on an mRNA molecule

anticodon = 3 nucleotides on a tRNA molecule

anticodon

tRNA is responsible for bringing amino acids to theribosome. tRNA has an anticodon, which is the opposite ofthe mRNA codon.It is important to remember that the mRNA codon determines the amino acid, NOT the tRNA anticodon.

mRNA:tRNA:aminoacid:

U U A C G A A G C U C GA A U G C U U C G A G C

Leucine - Arginine - Serine - Serine

Transcription vs. Translation Review

Transcription• Process by which genetic

information encoded in DNA is copied onto messenger RNA

• Occurs in the nucleus• DNA mRNA

Translation• Process by which

information encoded in mRNA is used to assemble a protein at a ribosome

• Occurs on a Ribosome• mRNA protein

DNA:

mRNA:

tRNA:

amino acids:

TAC AAG CTT GGG ATA CGC TAA ATT

UUC GAA CCC UAU GCG AUU UAA

AAG CUU GGG AUA CGC UAA AUU

Phenylalanine - Glutamic Acid - Proline - Tyrosine - Alanine - Isoleucine - Stop

**Remember – use the mRNA codons to determine the amino acids!! NOT the Anti codons

Complete the Following Chart:

AUG

UAC

Start -