BIOLOGY CHAPTER 13 RNA and Protein Synthesis I

BIOLOGY CHAPTER 13 RNA and Protein Synthesis

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

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

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)

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

5. In Eukaryotes… there may be RNA editing (pieces removed) a. INTRONS – discarded portions of m. RNA b. EXONS – remaining pieces of m. RNA which are expressed http: //www. stolaf. edu/people/giannini/flashanimat/molgeneti cs/transcription. swf

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

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 m. RNA 1. Start Codon – AUG (methionine) 2. Stop Codons – UGA, UAG

IV. Translation Converting an m. RNA sequence into an amino acid sequence A. TRANSLATION – B. t. RNA is the amino acid carrier. 3 -base sequence on the end of a t. RNA molecule It is complementary to a codon! 1. ANTICODON:

• • • C. Translation Sequence: (at the ribosomes) 1. 6 -base section of m. RNA is held in place; 2 t. RNA molecules match to codons; dehydration synthesis forms bonds between amino acids 2. after peptide bond forms, 1 st t. RNA is released ribosome moves 3 bases 3. another t. RNA/amino acid moves into place new peptide bond forms process repeats until “stop” codon is reached • http: //vcell. ndsu. edu/animations/translation/movie. htm

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

V. Mutations [13. 3] Inheritable changes at the of nucleotides (changes in base sequence) A. GENE MUTATIONS – level 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)

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 http: //www. rcsb. org/pdb/explore/jmol. do? structure. Id=4 HHB &opt=3&bionumber=1

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

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 THE CAT ICA ATE TAT TET THE RAT ETH ERA T HER AT INSERTION DELETION

• 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

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

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

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

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

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

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

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

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.

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 http: //highered. mcgraw-hill. com/olc/dl/120080/bio 27. swf http: //bcs. whfreeman. com/thelifewire/content/chp 13/1302001. html

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.

• 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)