1. RNA and Protein Synthesis
Chapter 13
(Pgs Miller and Levine Biology text)

2. Where have we seen DNA being replicated?
MITOSIS AND MEIOSIS

3. Proteins are molecules that are necessary for virtually every activity in your body. Some of the Biological Functions of Proteins include:

4. Genotype  Phenotype DNA mRNA tRNA PROTEIN
Transcription Translation

5. How are DNA and RNA different?
Nucleotides = deoxyribose sugar
Double helix structure
Stays inside nucleus
RNA…
Nuleotides = ribose sugar
Single-strand structure
Located both inside and outside of nucleus
Uracil instead of thymine

6. How are DNA and RNA different?

7. A Closer Look at RNA:
Contains ribose sugar instead of deoxyribose sugar
Single stranded
The nucleotide uracil replaces thymine

8. 3 Types of RNA Messenger RNA = mRNA
-Carries genetic coded message sequence from DNA, in the nucleus to the ribosome in the cytoplasm.
Ribosomal RNA = rRNA
- One of components of the
ribosome, rRNA associates with protein to form the ribosome. There are 1000’s of ribosomes/cell.
-Ribosomal RNA (rRNA) is part of the ribosome. rRNA consists of two subunits that are made up of several ribosomal RNA. Proteins are assembled on the ribosomes.
Transfer RNA = tRNA
- Transfer RNA (tRNA) transfers each amino acid to the ribosome as it is specified by the coded messages in mRNA. Transfer RNA carries amino acids to the ribosome and matches them to the coded mRNA message. There is one specific tRNA for each amino acid.

10. Transcription mRNA – stands for messenger RNA
it is the copy of the DNA message for making a protein
Occurs in the nucleus
Promoter region on DNA marks where transcription should start and terminator region marks where it should stop

11. Basic Principles of Transcription and Translation
Is the synthesis of RNA under the direction of DNA
Produces messenger RNA (mRNA)
In transcription, segments of DNA serve as templates to produce complementary RNA molecules.
In eukaryotes, RNA is produced in the cell’s nucleus and then moves to the cytoplasm.

12. Transcription requires an enzyme known as RNA polymerase.
Binds to DNA during transcription and separates the DNA strands.
It uses one strand of DNA as a template to create a complementary strand of RNA.

13. RNA polymerase only binds to promoters, which are regions of DNA that have specific base sequences.
Before it becomes mRNA, it is called pre-mRNA. Pre-mRNA molecules have bits and pieces cut out of them before they can go into action. The portions that are cut out are called introns.
The remaining pieces, known as exons, are then spliced back together to form the final mRNA.

14. Genes have a complex internal organization
Introns-DNA sequences present in some genes that transcribed BUT are removed during processing and therefore are not present in mRNA.
Exons-DNA sequence that are transcribed and joined to other exons during mRNA processing and are translated into amino acid sequence of a protein

15. 19. Processing Pre-mRNA

17. In eukaryotes RNA transcripts are modified before becoming true mRNA
Eukaryotic cell. The nucleus provides a separate compartment for transcription. The original RNA transcript, called pre-mRNA, is processed in various
ways before leaving the nucleus as mRNA.
(b)
TRANSCRIPTION
RNA PROCESSING
TRANSLATION
mRNA
DNA
Pre-mRNA
Polypeptide
Ribosome
Nuclear
envelope

18. mRNA
No T (thymine) so when it reads the nucleotide A on DNA it matches it with ____?

19. Protein Synthesis= transcription and translation
DNA contains all the information for your traits – the genes
These genes are blueprints and need to remain safe – kept inside the nucleus
Copies can be made though – a messenger

20. Section 13.2 Ribosomes and Protein Synthesis
Proteins are made by joining amino acids together into long chains called polypeptides.
20 different amino acids are commonly found in polypeptides.
RNA contains four different bases:
Adenine, cytosine, guanine, and uracil.

21. Codons
The genetic code is read three letters at a time, so that each words is three bases long and corresponds to a single amino acid.
Each three letter “word” is called a codon.

22. How to Read Codons
Most amino acids can be specified by more than one codon.
UUA, UUG, CUU, CUC, CUA, and CUG all code for leucine.
It’s time to code! Look at page 367 of your book and follow the steps in figure 13-6.

23. Start and Stop Codons
The start (initiation) codon for protein synthesis is AUG, which codes for the amino acid, methionine.
mRNA continues to be read, three bases at a time, until it reaches a stop codon. This ends translation and the polypeptide is complete.

24. Let’s practice coding!
If given the following DNA sequence, determine the mRNA sequence transcribed for this gene. Then determine the amino acid sequence of the polypeptide using the codon chart.
DNA: T A C A A G T C C A C A A T C

25. STOP codons: UAA, UAG, UGA
DNA: T A C G A C A A G T C C A C A A T C
mRNA: A U G C U G U U C AGG UG UU A G
Leucine-phenylalanine-arginine-cysteine-stop.
Wait, why did we stop?
STOP codons: UAA, UAG, UGA

26. Translation
mRNA gives instructions on the order in which amino acids should be joined to produce a polypeptide.
Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains.
Translation is the process of decoding an mRNA message into a protein.

27. Transcription is carried on in the cell’s nucleus.
Translation is carried out by ribosomes after the transcribed mRNA enters the cell’s cytoplasm.

28. Steps to Translation
1. Translation begins when a ribosome attaches to an mRNA molecule in the cytoplasm. 2. tRNA brings the proper amino acid into the ribosome. One at a time, the ribosome attaches these amino acids to the growing chain.

29. A Little Info about tRNA
Each tRNA molecule carries just one kind of amino acid and it contains three unpaired bases. These are called the anticodon.
HOLD UP Mrs. Wald…. WHAT?! A codon and an anticodon? Please explain.

30. Anticodon

31. Molecules of tRNA are not all identical
TRANSCRIPTION
TRANSLATION
DNA
mRNA
Ribosome
Polypeptide
Amino
acids
tRNA with
amino acid
attached
tRNA
Anticodon
Trp
Phe
Gly A G C U
Codons 5 3
Molecules of tRNA are not all identical
1. Each carries a specific amino acid on one end
2. Each has an anticodon on the other end

32. AUG UAC Great, so what’s the amino acid? Do you use AUG or UAC?
If you are provided the codon:
AUG
The anticodon (which is located on tRNA) is:
UAC
Great, so what’s the amino acid? Do you use AUG or UAC?
You use the codon, so AUG, which codes for the amino acid methionine.

33. Let’s continue with tRNA
3. The ribosome joins the amino acids in the binding sites and tRNA floats away from the ribosome. This creates a peptide chain!
4. The process continues until the ribosome reaches one of three of the stop condons.

34. 3 Forms of RNA
All three forms of RNA come together during translation.
mRNA carries the coded message.
tRNA delivers the correct amino acid.
Ribosomes are composed of roughly 80 proteins and 3 or 4 rRNA molecules.
rRNA helps hold ribosomal proteins in place and locate the beginning of the mRNA message.

35. The Central Dogma of Biology
Proteins have everything to do with traits!
The central dogma of molecular biology is that information is transferred from DNA to RNA to protein.

36. mRNA Transcribes DNA message and carries it to ribosome
RNA polymerse is the enzyme that produces it
CLICK ON PICTURE FOR ANIMATION ON TRANSCRIPTION

37. tRNA Once mRNA is made it attaches to a ribosome
tRNA = transfer RNA and they carry amino acids
Amino acids are the building blocks of proteins (remember?)

39. During transcription
The gene determines the sequence of bases along the length of an mRNA molecule
DNA
molecule
Gene 1
Gene 2
Gene 3
DNA strand
(template)
TRANSCRIPTION
mRNA
Protein
TRANSLATION
Amino acid A C G T U
Trp
Phe
Gly
Ser
Codon 3 5

40. Figure 12–14 Transcription
Section 12-3
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA polymerase
DNA
RNA

41. From the DNA sequence below, write the complementary DNA sequence:
TGA TTT CGG TAC GAT TAA CAA CCT CGA ATT
ACT AAA GCC ATG CTA ATT GTT GGT GCT TAA
If the top DNA strand encodes the message to make a protein, then what will the transcribed M-RNA be:
ACU AAA GCC AUG CUA AUU GUU GGA GAU UAA

42. Codon = mRNA Anti-codon = tRNA

43. A tRNA molecule
Consists of a single RNA strand that is only about 80 nucleotides long
Is roughly L-shaped
Two-dimensional structure. The four base-paired regions and three loops are characteristic of all tRNAs, as is the base sequence of the amino acid attachment site at the 3 end. The anticodon triplet is unique to each tRNA type. (The asterisks mark bases that have been chemically modified, a characteristic of tRNA.)
(a) 3 C A G U * 5
Amino acid
attachment site
Hydrogen
bonds
Anticodon

44. Molecular Components of Translation
A cell translates an mRNA message into protein
With the help of transfer RNA (tRNA)

45. Molecular Components of Transcription
RNA synthesis
Is catalyzed by RNA polymerase, which pries the DNA strands apart and hooks together the RNA nucleotides
Follows the same base-pairing rules as DNA, except that in RNA, uracil substitutes for thymine

46. Comparing RNA & DNA DNA RNA Nucleotide Deoxyribose Ribose
Single-stranded
Double-stranded
Nitrogenous bases X X X X X X X X

47. Comparing RNA & DNA DNA RNA Thymine Uracil
Template for synthesis of nucleic acid
Double helix
Replication
Transcription X X X X X X X

48. Comparing RNA & DNA DNA RNA Exact Copy Messenger More Than 1 Form
Found in Nucleus
Leaves Nucleus
Does not Leave X X X X X X X

49. RNA Concept Map RNA mRNA rRNA tRNA can be also called
which functions to
also called
which functions to
also called
which functions to
Messenger RNA
Carry instructions
Ribosomal RNA
Combine with
protein
Transfer RNA
Brings amino acids
to the ribosome
from to
to make up
Ribosomes
Ribosomes
DNA