1. Transcription and Translation
Genes to Proteins
Transcription
and
Translation

2. DNA  RNA  Protein
DNA contains genes which provide the information necessary to make proteins
Different versions of the same gene result in different versions or amounts of a protein, and the differences in the protein result in different characteristics
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein

3. Don’t let this happen to you!!

4. RNA How does RNA (ribonucleic acid)
differ from DNA (deoxyribonucleic acid)?
RNA has a sugar ribose
DNA has a sugar deoxyribose
RNA contains uracil (U)
DNA has thymine (T)
RNA molecule is single-stranded
DNA is double-stranded

5. Transcription
The process that copies the message in a gene into a messenger RNA (mRNA) molecule that will provide the instructions for making a protein molecule
Started and controlled by an enzyme called RNA polymerase.
RNA polymerase binds to the DNA at a special point (start signal)
RNA polymerase unwinds and separates the two DNA strands
RNA polymerase adds and links complementary RNA nucleotides as it “reads” the gene until it reaches a “stop” signal
RNA
polymerase
DNA
mRNA

6. Transcription

8. Products of Transcription
Ribosomal RNA (rRNA) – Carrier molecule on ribosomes – holds the tRNA and mRNA in place
Transfer RNA (tRNA) - The molecule that physically couples nucleic acid codons with specific amino acids
Messenger RNA (mRNA) - The messenger that carries information from genes on DNA to the protein manufacturing ribosomes

9. Translation The process that makes proteins
Translation The process that makes proteins. The sequence of nucleotides in an mRNA molecule specifies the sequence of amino acids in a protein.
This is a molecule of messenger RNA. It was made in the nucleus by transcription from a DNA molecule.
Codon= series of three nucleotides
A U G G G C U U A A A G C A G U G C A C G U U
mRNA molecule

10. Messenger RNA (mRNA) Primary structure of a protein
Each codon translates into one of twenty amino acids or is a stop or start signal A U G C
mRNA
start
codon
codon 2
codon 3
codon 4
codon 5
codon 6
codon 7
codon 1
methionine
glycine
serine
isoleucine
alanine
stop
codon
protein
Primary structure of a protein
aa1
aa2
aa3
aa4
aa5
aa6
peptide bonds

11. The Genetic Code UUU UUC UUA UUG CUU CUC CUA CUG AUU AUC AUA AUG GUU
GUC
GUA
GUG
UCU
UCC
UCA
UCG
CCU
CCC
CCA
CCG
ACU
ACC
ACA
ACG
GCU
GCC
GCA
GCG
UAU
UAC
UAA
UAG
CAU
CAC
CAA
CAG
AAU
AAC
AAA
AAG
GAU
GAC
GAA
GAG
UGU
UGC
UGA
UGG
CGU
CGC
CGA
CGG
AGU
AGC
AGA
AGG
GGU
GGC
GGA
GGG
Phenylalanine
Leucine
Valine
Serine
Proline
Threonine
Alanine
Tyrosine
Stop
Histidine
Glutamine
Asparagine
Lysine
Glutamic
Acid
Cysteine
Arginine
Serine
Glycine
Stop
Tryptophan
Isoleucine
Methionine

12. Note that 3rd Base Position is Variable

13. Eukaryotic Cell Protein Synthesis

14. Protein Synthesis occurs on Ribosomes

15. Protein Synthesis occurs on Ribosomes
A ribosome on the rough endoplasmic reticulum attaches to the mRNA molecule.
ribosome
A U G G G C U U A A A G C A G U G C A C G U U

16. Along comes a Transfer RNA Molecule…
amino acid
attachment site U A C
anticodon
methionine
amino acid

17. A U G G G C U U A A A G C A G U G C A C G U U
Amino acid
U A C
tRNA molecule
The tRNA brings an amino acid to the first three bases (codon) on the mRNA.
The three unpaired bases (anticodon) on the tRNA link up with the codon.
anticodon
A U G G G C U U A A A G C A G U G C A C G U U

18. U A C
C C G
Another tRNA molecule comes into place, bringing a second amino acid.
Its anticodon links up with the second codon on the mRNA.
A U G G G C U U A A A G C A G U G C A C G U U

19. U A C
C C G
Peptide bond
A peptide bond forms between the two amino acids.
A U G G G C U U A A A G C A G U G C A C G U U

20. U A C
C C G
The first tRNA molecule releases its amino acid and moves off into the cytoplasm.
A U G G G C U U A A A G C A G U G C A C G U U

21. C C G
The ribosome moves along the mRNA to the next codon.
A U G G G C U U A A A G C A G U G C A C G U U

22. C C G
A A U
Another tRNA molecule brings the next amino acid into place.
A U G G G C U U A A A G C A G U G C A C G U U

23. C C G
C C G
A peptide bond joins the second and third amino acids to form a polypeptide chain.
A U G G G C U U A A A G C A G U G C A C G U U

24. A C G
G U C
The process continues.
The polypeptide chain gets longer.
This continues until a termination (stop) codon is reached.
The polypeptide is then complete.
A U G G G C U U A A A G C A G U G C A C G U U

25. There is a tunnel through the large subunit of the ribosome that allows the growing polypeptide chain to pass out of the ribosome

26. Termination of translation is triggered by stop codons
A release factor enters the A site and triggers hydrolysis of the peptidyl-tRNA bond leading to the release of the protein.

27. Release of the protein causes the disassociation of the ribosome into its constituent subunits.

28. Transcription And Translation In Prokaryotes3’ 5’ 5’
mRNA
RNA
Pol.
Ribosome
Ribosome
Everything happens in the nucleus

29. Eukaryotic Transcription
DNA
Cytoplasm
Nucleus
Nuclear
pores
RNA
Transcription G
AAAAAA
RNA
Processing
mRNA
Export G
AAAAAA

30. Eukaryotic Translation

31. Transcription/Translation Quiz
What is transcription?
Production of RNA molecules by copying part of DNA into a complementary sequence of RNA
Why is transcription necessary?
Transcription makes messenger RNA (mRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.
Describe transcription.
RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble mRNA. It uses the nucleotide bases except it replaces Thymine with Uracil

32. Transcription/Translation Quiz
What is translation?
The genetic message encoded in RNA is used to create a polypeptide with a specific amino acid sequence
Describe translation.
The cell uses information from mRNA and tRNA to produce proteins.
Why is translation necessary?
Translation assures that the right amino acids are joined together by peptides to form the correct protein.
What are the main differences between DNA and RNA?
DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.