Protein Synthesis Molecular Genetics:
Protein Synthesis
Molecular Genetics:
BackgroundThe structure of DNA explains how DNA can be copied but it does not
explain how genes work.Genes are coded DNA instructions that
control the production of proteins within the cell.
What are proteins?•Chains of amino acids
•Amino acids (created based on the sequence of the nitrogen bases)
•Sequence of nitrogen bases => amino acids => proteins
Why are proteins important?1.Control biochemical pathways
2.Direct the formation of lipids, carbohydrates, and nucleotides
3. Responsible for the cell’s structure and movement
Before a protein can be put togetherit all starts with DNA.
ProblemDNA is inside of the nucleus but the
ribosomes that make proteins are in the cytoplasm.
It uses RNA!RNA takes the instructions to make
proteins to the Ribosome
How does DNA pass the instructions to
the ribosome?
DNA(nucleus)
RNA(cytoplasm)
Protein(ribosome)
transcription
translation
The Structure of RNA(Ribonucleic Acid)
•Single chain of nucleotides (1/2 of a ladder)•Sugar (ribose)•Phosphate group•Nitrogen bases (A,U, C, G)•3 types of RNA (mRNA, tRNA, rRNA)
mRNA (messenger)Carries the instructions (MESSAGE)for assembling amino acids into proteins.
mRNA
nucleus
linear
rRNA (ribosomal)• Proteins are assembled on
ribosomes.• Ribosomes made up of several
types of proteins, as well a type of RNA called rRNA (r = RIBOSOMAL).
globular
Pharm201 Lecture 2 2008 11
The Ribosome: Details• Complex of protein
and RNA• Small 30S subunit –
controls interactions between mRNA and tRNA
• Large 50S subunit – peptide transfer and formation of the peptide bond
tRNA (transfer)When a protein is being made,
tRNA molecules TRANSFER each amino acid to the ribosome as told by the specific coded message of
mRNA.
tRNA
Amino Acid
hairpin
Passing of Info from DNA to RNA is called
Process of copying a strand of DNAinto a complementary strand of RNA
Transcription
DNA RNA Proteins
Steps of Transcription1. DNA is copied into a strand of RNA inside of the
nucleus.A bonds with UracilC bonds with G
A
T
C
A
A
U
U
G
DNA RNA
RememberNO “T” in RNA
Draw diagram
2. mRNA leaves the nucleus and goes to the ribosomes
Transcription (continued)
Nucleus
mRNA
• Transcription Animation
• Protein Synthesis Interactive
TranslationTaking the instructions from mRNA and producing proteins
1.The mRNA arrives at the ribosome
2. tRNA (transfer RNA) brings free floating amino acids to the mRNA
3.The mRNA and tRNA match correct bases
4. The amino acids then bond to each other creating a protein chain
Nucleus
Ribosome
Nucleus
mRNACodon
anticodon
Amino acidtRNA
mRNA
tRNA
Protein
Codon
anticodon
Protein
Genetic CodeThe “language” of mRNA instructions iscalled the genetic code. RNA containsfour bases, A,U,G, & C. The code is written using 4 letters only.
There are 4 nitrogen bases, which combineto make 64 different codons, which make
20 different amino acids.
Genetic Code
AUGC= 64 codons = 20 amino acids
Codon = 3 nucleotides = 1 specific amino acid
RNA Strand = UCGCACGGU
This would be read 3 bases at a time
UCG – CAC - GGUThese codons represent amino acids
Serine – Histidine - Glycine
GCU
AAA
UCC
DNA vs. RNA
Transcription (elongation) (2)
/antisense strand