1. Types of RNA TRANSCRIPTION translation
CHAPTER 8, PART 2

2. RNA and Protein Synthesis
Genes are coded DNA instructions that control the production of proteins.
Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA.
RNA contains coded information for making proteins.

3. THE STRUCTURE OF RNA RNA Polymer – long chain of repeating units
Nucleic Acid
Monomer – repeating units that make a polymer
Nucleotide
Phosphate
Ribose (a sugar containing 5 carbons)
Nitrogenous bases
Adenine
Uracil
Guanine
Cytosine

4. THE STRUCTURE OF RNA Three main differences between RNA and DNA
The sugar in RNA is ribose instead of deoxyribose.
RNA is generally single-stranded.
RNA contains uracil in place of thymine.

5. THE STRUCTURE OF RNA
Three main differences between RNA and DNA

6. THE STRUCTURE OF RNA There are three main types of RNA: messenger RNA
(mRNA) carries copies of instructions for assembling amino acids into proteins.
Moves from nucleus to ribosome

7. THE STRUCTURE OF RNA There are three main types of RNA: ribosomal RNA
Ribosomes are made up of proteins and ribosomal RNA (rRNA).

8. THE STRUCTURE OF RNA There are three main types of RNA: transfer RNA
During protein synthesis, transfer RNA (tRNA) transfers each amino acid to the ribosome.

9. PROTEIN SYNTHESIS DNA molecule DNA strand (template) 3¢ 5¢
TRANSCRIPTION
mRNA 5¢ 3¢
Codon
TRANSLATION
Protein
Amino acid

10. Protein synthesis Transcription Purpose
The first step to building a protein
Copies the information from DNA into a form of RNA
Occurs inside the nucleus
Purpose
One segment of DNA codes for one protein
Since DNA can’t leave the nucleus (and proteins can’t be made in the nucleus) RNA must be made
DNA double helix produces 1 RNA single helix
Only one template strand of DNA is used, the other just waits for the process to end
Begins at a section of DNA called a promoter.

11. Protein synthesis Transcription Step 1 Initiation
DNA helicase unwinds the DNA strand temporarily (it will go back together)
Makes room for the RNA strand to be built
RNA Polymerase (enzyme) binds to promoter (special code) on DNA
Gives a signal to tell transcription to start

12. Protein synthesis Transcription Step 2
Elongation
RNA polymerase brings one RNA nucleotide at a time to bind with complementary DNA bases
A-U, T-A
G-C
Occurs in 5’ to 3’ direction
Creates an antiparallel RNA strand
Only happens on one template strand of DNA
AKA: Coding Strand, Template Strand
RNA polymerase edits as it goes

13. Protein synthesis
Transcription
Step 2
Elongation

14. Protein synthesis Transcription Step 3 Termination
Ends when RNA Polymerase reaches stop code (stop codon)
DNA goes back to normal
Hydrogen bonds reform
RNA is released from the DNA strand but has to be edited first, before leaving the nucleus

15. Protein synthesis Transcription RNA Editing
The whole mRNA that is made in transcription has too many bases, it must be made smaller.
Some DNA within a gene is not needed to produce a protein.
These areas are called introns.
They stay INSIDE the nucleus.
The DNA sequences that code for proteins are called exons.
This finished RNA EXITS the nucleus.

16. Protein synthesis
Transcription
RNA Editing

17. Protein synthesis The Genetic Code
The “language” of mRNA instructions, written by using the letters of the nitrogenous bases: A, U, C, G.
3 bases in a row on mRNA codes for one amino acid (the monomer of a protein)
These three consecutive nucleotides are better known as a codon
a section of mRNA that specifies a particular amino acid.

18. Protein synthesis The Genetic Code Each codon codes for an amino acid
Some codons code for the same amino acid
64 possible codons (combinations of A, U, C, G triplets)
20 amino acids (monomer of a polypeptide)
Some codons actually don’t code for an amino acid, but to stop building the protein
Genetic Code charts are used to determine the amino acid that a codon is coding for.

19. Protein synthesis
The Genetic Code

20. Protein synthesis Translation Happens on ribosomes
The cell uses information from mRNA to produce proteins.
RNAProtein
Happens on ribosomes
Involves all 3 types of RNA
3 Steps
Initiation
Elongation
Termination
End result: formation of a polypeptide (protein)
The polypeptide becomes a protein when it is folded into a specific shape (usually in the Golgi Complex)

21. Protein synthesis Translation mRNA tRNA rRNA 2 subunits Single strand
Made in the nucleus
Sends message from DNA to the ribosome to build a protein
Arranged in codons
tRNA
Transfer RNA
Has 3 loops of RNA and one amino acid
Loop opposite the amino acid has the anticodon
3 base sequence complimentary to mRNA codon
No anticodon for Stop Codons UAG, UAA, OR UGA
rRNA
2 subunits
Large ribosomal subunit
Small ribosomal subunit
Only come together during translation
Acts as an enzyme to put together amino acids and form the polypeptide

22. Protein synthesis Translation
Overview:
mRNA codons are “decoded” by tRNA anticodons
tRNA brings amino acids to ribosomes according to mRNA codon sequence
The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA.
Amino acids join to form a polypeptide
ribosome
mRNA
Start Codon

23. Protein synthesis Translation Step 1: Initiation Step 2: Elongation
mRNA binds to the ribosome
The codon AUG signals translation to start
tRNA with anticodon UAC brings Methionine
Always the first amino acid in a protein
Step 2: Elongation
2nd tRNA lands on ribosomal binding site
Methionine and 2nd amino acid join together, by peptide bond
slides over bringing the mRNA and AA chain along and kicking off the 1st tRNA
Occurs over and over again, until…
Step 3: Termination
When the mRNA codon UAA, UGA, or UAG is reached, translation stops
There are no amino acids on tRNA with anticodons that match with the STOP codons
The ribosomal subunits dissociate
The polypeptide chain goes to be processed into a completed protein

24. Protein synthesis Translation Messenger RNA nucleus Phenylalanine tRNA
Messenger RNA is transcribed in the nucleus.
nucleus
Phenylalanine
tRNA
Lysine
mRNA
Methionine
Transfer RNA
The mRNA 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.
Ribosome

25. Protein synthesis Translation 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
Ribosome
tRNA
Lysine
tRNA
mRNA
mRNA
Completing the Polypeptide
The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
Translation direction
Ribosome

26. Amino acids within a polypeptide
Protein synthesis
Translation
Codon
Codon
Codon
DNA
mRNA
Protein
Single strand of DNA
Codon
Codon
Codon
mRNA
Alanine
Arginine
Leucine
Amino acids within a polypeptide

27. Protein synthesis REVIEW
The role of a master plan in a building is similar to the role of which molecule?
messenger RNA
DNA
transfer RNA
ribosomal RNA

28. Protein synthesis REVIEW
A base that is present in RNA but NOT in DNA is:
Thymine
Uracil
Cytosine
Adenine

29. Protein synthesis REVIEW
The nucleic acid responsible for bringing individual amino acids to the ribosome is:
Transfer RNA
DNA
Messenger RNA
Ribosomal RNA

30. Protein synthesis REVIEW
A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the
intron
exon
promoter
codon

31. Protein synthesis REVIEW
A codon typically carries sufficient information to specify a(an)
single base pair in RNA.
single amino acid.
entire protein.
single base pair in DNA.

32. mutations
CHAPTER 12.4

33. mutations Changes in genetic material Types Gene Chromosomal
Mutations that produce changes in a single gene
Chromosomal
Mutations that produce changes in whole chromosomes

34. mutations Gene Mutations Point Mutations
A change in one or a few nucleotides
Occur at a single point in the DNA sequence.
Include substitutions, insertions, and deletions.
Substitution
Usually affect no more than a single amino acid
Usually not harmful, especially if the 3rd nucleotide in the codon is affected

35. mutations Gene Mutations Point Mutations Substitution
They are classified by the effect on the protein produced:
Silent mutations have no effect on the protein.
Missense mutations result in a single amino acid change in the translated sequence.
Nonsense mutations result in an amino acid codon being replaced by a “stop” codon. Nonsense mutations end translation prematurely and result in a truncated protein.

36. mutations Gene Mutations Point Mutations Frameshift Mutations
Mutations that shift the reading frame of the genetic message by inserting or deleting a nucleotide
The effects of insertions or deletions are more dramatic.
Affects codon groups on all or most amino acids after
Can cause catastrophic damage to the organism
Insertion: an extra base in inserted into a sequence

37. mutations Gene Mutations Point Mutations Frameshift Mutations
Deletion: loss of a single base that results in the shifting of the reading frame

38. mutations
Gene Mutations
Point Mutations
Frameshift Mutations

39. mutations Causes of Mutations Spontaneous Environmental Exposures
Occur randomly
Environmental Exposures
UV Rays
Drugs
Pollution
Hazardous Chemicals