1. RNA and Protein Synthesis
Biology Chapter 13
RNA and Protein Synthesis

2. B. Differences between DNA and RNA DNA RNA
I. RNA [13.1]
A. Describe RNA – Ribonucleic Acid
B. Differences between DNA and RNA
DNA
RNA
Deoxyribose
Ribose
Double-stranded
Single-stranded
G, C, A, Thymine
G, C, A, Uracil

3. C. Types of RNA 1. mRNA - (messenger RNA) carries protein synthesis instructions from nucleus to ribosomes 2. tRNA - (transfer RNA) carries amino acids to ribosomes, matches A. A. to mRNA 3. rRNA - (ribosomal RNA) forms portion of ribosomes (rest is protein)

4. II. Gene Expression (starting with RNA synthesis) [13.1]
A. TRANSCRIPTION (just a short description)-
Changing DNA codes into RNA codes
B. GENE – Portion of DNA which codes for a particular
protein
C. Enzyme involved – RNA Polymerase
D. PROMOTOR REGION – Region of DNA which is
recognized by RNA polymerase
(often multiple TACTACTAC triplets)

5. E. Sequence (of RNA Transcription) 1. Unwind section of DNA 2
E. Sequence (of RNA Transcription) 1. Unwind section of DNA 2. “Sense” strand of DNA is rewritten into a complementary strand of mRNA 3. Transcription proceeds from promoter region toward termination sequence 4. In Eukaryotes, mRNA moves out of the nucleus to ribosomes

6. 5. In Eukaryotes… there may be RNA editing (pieces removed) a
5. In Eukaryotes… there may be RNA editing (pieces removed) a. INTRONS – discarded portions of mRNA b. EXONS – remaining pieces of mRNA which are expressed

7. III. Reading the Genetic Code [13.2]
A. GENETIC CODE – Sequence of nitrogenous bases
B. There are 20 common amino acids; what led to the concept of the triplet code?
1. DNA has four nitrogenous bases: A, G, T, C
  a. If the match was 1 base: 1 amino acid, there would be __4___ possible amino acids
b. If the match was 2 bases: 1 amino acid, there would be __16___ possible amino acids
c. If the match was 3 bases: 1 amino acid, there would be __64___ possible amino acids

8. There are duplications and 3 stop codons
2. With that many possibilities, what happens to all the extra triplets?
There are duplications and 3 stop codons
C. CODON – 3-letter sequence of bases in mRNA
1. Start Codon – AUG (methionine)
2. Stop Codons – UGA, UAA, UAG

9. B. tRNA is the amino acid carrier.
IV. Translation
A. TRANSLATION – Converting an mRNA sequence into an amino acid sequence
  B. tRNA is the amino acid carrier.
1. ANTICODON: 3-base sequence on the end of a tRNA molecule
It is complementary to a codon!
Yikrazuul ({{Information |Description={{en|1=tRNA-Phe from yeast}} |Source={{own}} |Author=Yikrazuul |Date= |Permission= |other_versions= }} )

10. C. Translation Sequence: (at the ribosomes)
1. 6-base section of mRNA is held in place;
2 tRNA molecules match to codons;
dehydration synthesis forms bonds between amino acids
2. after peptide bond forms, 1st tRNA is released
ribosome moves 3 bases
3. another tRNA/amino acid moves into place
new peptide bond forms
process repeats until “stop” codon is reached

11. D. Central Dogma of Molecular Biology – Information is transferred from DNA to RNA to protein E. GENE EXPRESSION – Process by which DNA, RNA, and proteins are involved in putting a gene to work

12. Changes in one or a few nucleotides 2. SUBSTITUTIONS –
V. Mutations [13.3]
A. GENE MUTATIONS – Inheritable changes at the level of nucleotides (changes in base sequence)
1. POINT MUTATIONS –
  Changes in one or a few nucleotides
2. SUBSTITUTIONS –
  One base is exchanged for another
a. How will a base substitution affect the protein for which the affected gene codes?
1 amino acid is affected (or not –
depending on change)

13. a single nucleotide substitution (1 base in over 1000)
b. Example
i. The genetic cause of sickle-cell anemia is
 a single nucleotide substitution (1 base in over 1000)
ii. The effect of sickle-cell anemia is
 hemoglobin molecules form fibers – change the shape of red blood cells

14. All amino acids downstream will be affected and changed
3. FRAMESHIFT MUTATION –
Mutations which cause reading frame (3 letters or triplet) to move forward or backward
a. INSERTION –
Adding a base, shifts reading frame 1 base to the right
i. How will an INSERTION affect the protein for which the affected gene codes?
All amino acids downstream will be affected and changed

15. Removal of a base from a sequence
b. DELETION –
  Removal of a base from a sequence
i. How will a DELETION affect the protein for which the affected gene codes?
All the amino acids downstream from the mutation will change
THE CAT ATE THE RAT
THE ICA TAT ETH ERA T INSERTION
THE ATA TET HER AT DELETION

16. as opposed to frameshift that alters all the downstream amino acids
c. MISSENSE MUTATION – Single base change which alters one amino acid in a chain
as opposed to frameshift that alters all the downstream amino acids
d. NONSENSE MUTATION - Single base change which causes a stop codon to be transcribed, bringing transcription to an early halt

17. e. SILENT MUTATION - Single base change which alters a triplet, but translation produces the same amino acid (due to duplicate triplet codes)

18. B. CHROMOSOMAL MUTATION – change in structure of a chromosome
1. Quickly describe the effects of the following mutations:
a. DELETION –
removal (loss) of a section or a whole chromosome
b. DUPLICATION –
extra copy of a section or a whole chromosome
example: Trisomy 21, Trisomy 13

19. reversal of direction of a section of chromosome
c. INVERSION –
reversal of direction of a section of chromosome
d. TRANSLOCATION –
part of one chromosome gets moved from one to another

20. C. Causes of Mutations and Cancer– 1. MUTAGEN –
agent which can cause a mutation
a. Examples –
UV light, Pesticides, X-rays,
2. CARCINOGEN
mutagen which can specifically cause cancer

21. D. How can mutations be harmful to organisms?
Cell Death
Cancer
E. How can mutations be helpful to organisms?
New genetic combinations – may improve on previous condition

22. Group of genes that are regulated together
VI. Gene Regulation [13.4]
A. A Prokaryotic Example – The Lac Operon
B. Vocabulary
1. OPERON –
Group of genes that are regulated together
2. OPERATOR –
 Portion of DNA which can prevent access to structural genes

23. C. The lac operon produces –
3. REPRESSOR –
 Molecule which binds to operator – prevents transcription
4. INDUCER –
Molecule which changes shape of repressor; this allows RNA polymerase access to structural genes
C. The lac operon produces –
Galactosidase

24. D. Sequence of events
1. In order to produce beta galactosidase, RNA polymerase must (first) bind to – promoter region
2. In the “off” mode, a ___repressor___ __protein____ is bound to
the ___operator__ ____region__ of the lac operon.

25. D. Sequence of events
3. When the operon turns “on”, lactose binds to the __repressor__.
4. The _shape__ _of_ _the_ _repressor_ is changed and it can no
longer bind to the ____operator_____.
5. Without the repressor in place –
transcription can take place

26. no energy is spent for an enzyme which is unneeded
E. Repressing the production of an enzyme has an advantage for the organism –
no energy is spent for an enzyme which is unneeded
(lactose is the substrate and the inducer in this system)
F. Gene regulation in eukaryotes is much more complicated.

27. Additional notes (due to my mistakes)
Mutation Vocabulary
Missense – Single base change which alters one amino acid in a chain
As opposed to frameshift that alters all the downstream amino acids
Nonsense – Single base change which causes a stop codon to be transcribed, bringing transcription to an early halt
Silent mutation – Single base change which alters a triplet, but translation produces the same amino acid (due to duplicate triplet codes)