PROTEIN SYNTHESIS

DNA vs. RNA

DNA

• Made of deoxyribose sugar

• A - C - G - Thymine• Located in nucleus• Stores genetic info• Double Stranded

RNA• Made of ribose sugar• A - C - G - Uracil• Transfers genetic

info• Single Stranded• Located in nucleus

and cytoplasm

What are proteins?• Organic compounds made of long chains of amino acids

(1000’s) in a certain sequence that coil together.

• The sequence of amino acids determine the type of protein

Types of RNA• mRNA- messenger RNA

– Takes information from DNA to ribosomes- transcription

– Long single stranded molecule

• tRNA- transfer RNA– Transports amino acids & takes them to the ribosomes

to be assembled- translation – Cloverleaf shape

• rRNA- ribosomal RNA– Along with proteins it makes up the ribosomes

STEPS OF PROTEIN SYNTHESIS

Transcription

• Process of converting the DNA code into an mRNA code– Location: Nucleus – Type of RNA involved mRNA

Steps of Transcription

1. RNA polymerase (an enzyme) binds to a region of DNA called a promoter (start pt for a gene)

2. DNA molecule unwinds3. Complimentary base pairs are added on to

an RNA molecule as was done in replication (Uracil binds with Adenine)

4. When mRNA reaches a termination codon it stops and releases from the DNA molecule

mRNA base pairings

• Nitrogen base sequence of DNA: A A G A A T A G G G T C T C A G C A C G C C C A A A A

• mRNA would be built with the following base sequence:

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

When mRNA reaches a STOP CODON it stops and releases from DNA molecule.

CODONS• Group of 3 nucleotide bases that will code

for a specific amino acid (correct this on your notes sheet).

• Refer to your chart on the last page to see how each codon codes for one of the 20 amino acids

• SPECIAL CODONS:– Start: AUG --> tells ribosomes to begin adding

amino acids– Stop: UAA; UAG; UGA --> tells ribosomes to

stop adding amino acids

Example mRNA codons

• U U C / U U A / U C C / C A G / A G U / C G U / G C G / G G U / U U U

Translation• Process that occurs along the ribosomes in

which the mRNA codons are read and the tRNA finds the corresponding amino acid that matches the mRNA codon (refer to chart)

• Location: Cytoplasm

• Type of RNA involved: mRNA and tRNA

Steps of Translation1. mRNA will migrate from the nucleus to a ribosome

(made of rRNA and protein)2. A tRNA will have a codon opposite that of the mRNA’s

codons called an anticodon.

The tRNA’s anticodon is UAC. This will be received in the ribosomes if the mRNA codon is AUG. This tRNA will thus pick up the amino acid Methionine (it is based on the codon not anticodon

Steps of TranslationThe anticodons of the tRNA’s will be

Codon Anti Codon Anti

U U C = AAG CGU= GCA

U U A = AAU GCG= CGC

U C C = AGG GGU= CCA

C A G = GUC UUU= AAA

A G U= UCA3. Each tRNA will hunt and find the appropriate amino acid

based on the codon (NOT it’s ANTICODON)

Protein Assembly

• The ribosome will line up the amino acids based on the order that the mRNA codons read and create peptide bonds between each amino acid. It is the tRNA’s job to go and get the correct amino acid.

Order of amino acid bases• Order of amino acids based on mRNA sequence:

(Use the amino acids chart & fill the rest of these in )

UUC / UUA / UCC / CAG / AGUPhenylalanine- CGU / GCG / GGU / UUU

Add this to your Notes:This would continue….most proteins are made of amino acid

sequences that are thousands of amino acids long.Once amino acid chain is completed the chain will twist into its

secondary and tertiary levels of organization to form the protein.

Codes for