1. DNA: Master Programmer
Stores genetic information
Specifies primary structure of proteins
Primary structure tertiary structure
Tertiary structure protein function
Control is indirect
DNA uses RNA

2. Why RNA? Why does DNA need to transfer genetic information to RNA?
DNA is found inside the nucleus. Ribosomes are outside the nucleus.
DNA does not leave nucleus
too large for nuclear pores
protection of the original instructions.
A way is needed to get genetic information from the DNA to the ribosomes to make proteins with amino acids.
Special molecule, messenger RNA (mRNA), performs this task with codons.

3. RNA: The Other Code RNA and Protein Synthesis A.The Structure of RNA
B. DNA and RNA Similarities/Differences
C. Types of RNA
D. Transcription/mRNA Synthesis
E. Protein Synthesis/Translation

4. RNA Structure

5. RNA/DNA Similarities long chain made of nucleotides
each nucleotide consists of:
a sugar
a phosphate
a nitrogen base
sugar and phosphate backbone

6. RNA/DNA Differences Different type of sugar (ribose)
Single strand rather than a double strand
RNA molecule is a disposable copy of DNA
Nitrogen base THYMINE found in DNA replaced by a similar base URACIL (U) in RNA
ex. ( A - U ) and ( C - G )
Three different types:
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)

7. Types of RNA Messenger RNA (mRNA)
Is a complimentary copy of a DNA segment
Single strand
Contains codons which code for specific amino acids.
Codons are triplet bases
Manufactured in the nucleus

8. Other Types of RNA Ribosomal RNA (rRNA) makes up majority of ribosome
made in the nucleolus
Transfer RNA (tRNA)
Carries amino acids to ribosome
Single strand looped back on itself
Anticodon-three nucleotides on tRNA are complementary to the three (codon) on the mRNA.
Matching of anticodon (tRNA) to codon (mRNA) allows the correct amino acid to be put in place.

9. Transfer RNA Structure

10. Bring amino acids to ribosome
Types of RNA: Summary
RNA
can be
Messenger RNA
Ribosomal RNA
Transfer RNA
also called
which functions to
also called
which functions to
also called
which functions to
mRNA
Carry instructions
rRNA
Combine
with proteins
tRNA
Bring amino acids to ribosome
from to
to make up
DNA
Ribosome
Ribosomes

11. RNA Synthesis: Transcription
Transcription- process by which one strand of DNA is copied to make a complementary strand of mRNA in the nucleus.
A strand (Sense strand) of DNA serves as a pattern for mRNA.
Enzymes “unzip” the two strands by breaking the hydrogen bonds.
RNA polymerase, an enzyme, inserts appropriate nitrogen bases.
Thymine (DNA) pairs with Adenine (RNA)
Adenine (DNA) pairs with Uracil (RNA)

12. Transcription RNA polymerase DNA RNA Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA polymerase
DNA
RNA

13. RNA Synthesis: Transcription
Transcription- process by which one strand of DNA is copied to make a complementary strand of mRNA in the nucleus.
enzymes
mRNA 5’C G G U A A C A U U A3’
DNA 3’G C C A T T G T A A T5’
enzymes
DNA 5’C G G T A A C A T T A3’

14. RNA Synthesis: Transcription
Three Stages:
Initiation
Attachment of RNA polymerase to DNA at promoter region
Elongation
Building of complimentary strand of RNA
Termination
Enzymes and transcript are released at terminator region

15. RNA Synthesis: Transcription
Processing RNA
Occurs in the nucleus
Attachment of cap on 5’ end
Methyl-guanine
Helps in attachment to ribosomes
Replacement of nucleotides on 3’ end
adenine tail
Poly-A tail
Determines life span of RNA
Removal of introns
RNA that doesn’t code for protein
Splicing of exons
Spliceosomes

16. DNA transcription by mRNA
DNA transcription by mRNA. Coloured transmission electron micrograph of DNA & mRNA (messenger RNA) molecules forming a feather-like, transcriptionally-active structure. This DNA is from the nucleus of an amphibian egg. The backbone of the feather, running down the image, is a long strand of DNA coated with protein. Numerous mRNA molecules extend in clusters from the DNA strand. Transcription of genetic information begins at one end of the gene, with the mRNA molecules growing longer as they approach completion. Transcription is the first step in protein synthesis. Magnification: x6700 at 6x4.5cm size.

17. Transcription Transcription:*
Transcription and Translation:
From DNA: the Secret of Life
RNA Splicing *
Translation: *
Translation animation review:

18. Transmission electron micrograph of the first demonstration of an individual gene and its transcription product RNA.

20. Protein Synthesis
A. Nucleotides in DNA have all the information to make proteins.
B. DNA code copied into mRNA
C. Proteins are made of amino acids which are coded from mRNA.
D. mRNA code is read in a triplet form called a CODON which specifies certain amino acids using a decoder (p.237 BSCS Blue)

21. The Genetic Code Decoder: Amino Acid Chart
BACK

22. Protein Synthesis: Translation
Translation -the decoding of the mRNA code into proteins
Only 20 amino acids make all life as we know it. How is this possible with only four nitrogen bases?
Code is in triplets --64 combinations
Codons on mRNA
Anticodons on tRNA
*AUG - codes for the amino acid methionine
Initiator codon
Always starts mRNA
Is often removed after protein is synthesized
*Some are “stop” codons
Terminator codon

23. Translation Messenger RNA Messenger RNA is transcribed in the nucleus.
mRNA
Lysine
Phenylalanine
tRNA
Transfer RNA
The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.
Methionine
Ribosome
mRNA
Start codon

24. Translation B. Transfer RNA
The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. B.
Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
mRNA
Lysine
Phenylalanine
tRNA
Methionine
Ribosome
mRNA
Start codon

25. Translation (continued)
The Polypeptide “Assembly Line”
The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. C.
Growing polypeptide chain
Ribosome
tRNA
Lysine
tRNA
mRNA
Completing the Polypeptide
The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
mRNA
Translation direction
Ribosome

26. Translation (continued)
The Polypeptide “Assembly Line”
The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.
Growing polypeptide chain D.
Completing the Polypeptide
The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
Ribosome
tRNA
Lysine
tRNA
mRNA
mRNA
Translation direction
Ribosome

27. Translation DNA 3oT A C T T T G T A A C T5o
enzymes
mRNA 5oA U G A A A C A U U G A3o

28. polypeptide chain of amino acids
mRNA
rRNA

29. Protein Synthesis: Translation
Same three stages as transcription
Initiation, elongation, termination
tRNA charging
Attaching the correct amino acid to the tRNA
Carried out by enzymes—one/amino acid
Bonds amino acid to it’s respective tRNA
Must be accurate for accurate protein synthesis
Ribosome Sites
P site—holds the tRNA and growing polypeptide chain
Named for the peptide chain
A Site—holds the next tRNA with the next amino acid
Named for amino acid
E Site—by the P Site, opposite the A Site
Named for exit

30. Translation - Initiation

31. Translation - Initiation

32. Translation - Initiation

33. Translation - Elongation

34. Translation - Elongation

35. Translation - Elongation

36. Translation - Termination

37. Translation - Termination

38. Translation - Termination

39. Transport and Modification of Proteins
Not all proteins are automatically functional
Chemically modified
Stabilized
Cut into smaller segments
Transported
Vesicles
Translated directly into Endoplasmic Reticulum
Signal sequence

40. Translation Errors Errors do occur Misreading nucleotide sequence
Initiation in wrong place
Frameshift in reading frame (codon)
Splicing mistakes
introns/exons
Changes in DNA
Frameshift
Stop codon
Not enough of an amino acid

41. Translation Transcription and Translation:*
from: DNA: The Secret of Life
Translation: *
Translation animation review:

43. Translation
Transcription and Translation:
Translation animation review: