1. FROM GENE TO PROTEIN

2. YOU MUST KNOW…
THE KEY TERMS GENE EXPRESSION, TRANSCRIPTION, AND TRANSLATION
HOW TO EXPLAIN THE PROCESS OF TRANSCRIPTION
HOW EUKARYOTIC CELLS MODIFY RNA AFTER TRANSCRIPTION
THE STEPS TO TRANSLATION
HOW POINT MUTATIONS CAN CHANGE THE AMINO ACID SEQUENCE OF A PROTEIN

3. CONCEPT 17.1
GENES SPECIFY PROTEINS VIA TRANSCRIPTION AND TRANSLATION

4. GENE EXPRESSION – THE PROCESS BY WHICH DNA DIRECTS THE SYNTHESIS OF PROTEINS
ONE GENE-ONE POLYPEPTIDE HYPOTHESIS – STATES THAT EACH GENE CODES FOR A POLYPEPTIDE
TRANSCRIPTION – THE SYNTHESIS OF RNA USING DNA AS A TEMPLATE IN THE NUCLEUS
mRNA IS PRODUCED DURING TRANSCRIPTION AND CARRIES THE GENETIC MESSAGE OF DNA TO THE RIBOSOME

5. DURING TRANSCRIPTION, ONLY ONE STRAND OF DNA IS TRANSCRIBED CALLED THE TEMPLATE STRAND
mRNA PRODUCED IS THE COMPLEMENTARY TO THE ORIGINAL DNA STRAND
mRNA BASE TRIPLETS ARE CODONS AND ARE WRITTEN IN THE 5’ TO 3’ DIRECTION
MORE THAN ONE CODON CODES FOR EACH OF THE 20 AMINO ACIDS

7. TRANSLATION IS THE PRODUCTION OF A POLYPEPTIDE CHAIN USING THE mRNA TRANSCRIPT AND OCCURS AT THE RIBOSOMES
INSTRUCTIONS FOR BUILDING THE POLYPEPTIDE CHAIN ARE WRITTEN IN A SERIES OF 3 NUCLEOTIDES CALLED A TRIPLET CODE (ANTICODON)

9. CONCEPT 17.2
TRANSCRIPTION IS THE DNA-DIRECTED SYNTHESIS OF RNA

10. RNA POLYMERASE IS THE ENZYME THAT SEPARATES THE 2 DNA STRANDS AND CONNECTS THE RNA NUCLEOTIDES AS THEY BASE-PAIR ALONG THE DNA TEMPLATE STRAND
PROMOTER – THE DNA SEQUENCES WHERE RNA POLYMERASE ATTACHES
TERMINATOR – THE DNA SEQUENCE SIGNALING THE END OF TRANSCRIPTION
TRANSCRIPTION UNIT – THE ENTIRE STRETCH OF DNA THAT IS TRANSCRIBED INTO AN RNA MOLECULE

11. 3 MAIN STAGES OF TRANSCRIPTION
INITIATION
IN BACTERIA, RNA POLYMERASE RECOGNIZES AND BINDS TO THE PROMOTER
IN EUKARYOTES, RNA POLYMERASE I, THE SPECIFIC RNA POLYMERASE THAT TRANSCRIBES mRNA, CANNOT BIND TO THE PROMOTER WITH SUPPORTING HELP FROM PROTEINS

12. 3 MAIN STAGES OF TRANSCRIPTION
ELONGATION
RNA POLYMERASE MOVES ALONG THE DNA CONTINUING TO UNTWIST THE DOUBLE HELIX
NUCLEOTIDES ARE CONTINUALLY ADDED TO THE 3’ END OF THE GROWING CHAIN
AS THE COMPLEX MOVES DOWN THE DNA STRAND, THE DOUBLE HELIX RE-FORMS, WITH THE NEW RNA MOLCULE STRAGGLING AWAY FROM THE DNA TEMPLATE

13. 3 MAIN STAGES OF TRANSCRIPTION
TERMINATION
AFTER RNA POLYMERASE TRANSCRIBES A TERMINATOR SEQUENCE IN THE DNA, THE RNA TRANSCRIPT IS RELEASED, AND THE POLYMERASE DETACHES

14. CONCEPT 17.3
EUKARYOTIC CELLS MODIFY RNA AFTER TRANSCRIPTION

15. A 5’ CAP AND A POLY- A TAIL ARE ADDED AND FACILITATE EXPORT OF mRNA FROM THE NUCLEUS, HELP PROTECT THE mRNA FROM DEGRADATION BY ENZYMES, AND FACILITATE THE ATTACHMENT OF THE mRNA TO THE RIBOSOME

16. RNA SPLICING TAKES PLACE IN EUKARYOTIC CELLS
LARGE PORTIONS OF THE NEWLY SYNTHESIZED RNA STRAND ARE REMOVED
THE SPLICED OUT SECTIONS ARE INTRONS, THE SECTIONS THAT REMAIN ARE EXONS
SPLICEOSOMES – SPLICE TOGETHER THE SECTIONS THAT REMAIN

18. RIBOZYME
WHEN RNA SERVES A CATALYTIC ROLE IN THE EXCISING OF THE INTRONS AND JOINING OF EXON
DID YOU KNOW…
FEWER THAN 25,000 GENES CAN MAKE APPROXIMATELY 100,000 POLYPEPTIDES

20. CONCEPT 17.4
TRANSLATION IS THE RNA-DIRECTED SYNTHESIS OF A POLYPEPTIDE

21. tRNA FUNCTIONS IN TRANSFERRING a. a. FROM A POOL OF a. a
tRNA FUNCTIONS IN TRANSFERRING a.a. FROM A POOL OF a.a. IN THE CELL’S CYTOPLASM TO A RIBOSOME
THE RIBOSOME ACCEPTS THE a.a. FROM tRNA AND INCORPORATES THE a.a. INTO A GROWING POLYPEPTIDE
EACH tRNA IS SPECIFIC FOR A PARTICULAR a.a. THE OTHER END HAS A NUCLEOTIDE TRIPLET CALLED AN ANTICODON WHICH ALLOWS IT TO PAIR WITH A COMPLEMENTARY CODON ON THE mRNA

22. A CODON IS AN mRNA TRIPLET
RESULTS IN 64 DIFFERENT CODONS
AS CODONS ARE READ, ONE a.a. IS ADDED TO THE CHAIN FOR EACH CODON READ
THE RULES FOR BASE-PAIRING BETWEEN THE THIRD BASE OF A CODON AND THE CORRESPONDING BASE OF A tRNA ANTICODON ARE NOT AS STRICT AS THOSE FOR DNA AND mRNA CODONS
RELAXATION OF BASE-PAIRING IS CALLED WOBBLE

24. rRNA COMPLEXES WITH PROTEINS TO FORM THE TWO SUBUNITS THAT FORM RIBOSOMES
RIBOSOMES HAVE 3 BINDING SITES FOR tRNA
P SITE – HOLDS THE tRNA THAT CARRIES THE GROWING POLYPEPTIDE CHAIN
A SITE – HOLDS THE tRNA THAT CARRIES THE a.a. THAT WILL BE ADDED TO THE CHAIN
E SITE – THE EXIT SITE FOR tRNA

26. 3 STAGES OF TRANSLATION
INITIATION – SMALL RIBOSOMAL SUBUNIT BINDS TO mRNA – AUG
tRNA WITH ANTICODON UAC, WHICH CARRIES THE a.a. METHIONINE, HYDROGEN BONDS TO FIRST CODON (HOLDS IT ALL TOGETHER)
LARGE SUBUNIT OF RIBOSOME ATTACHES, ALLOWING THE tRNA WITH METHIONINE TO ATTACH TO THE P SITE. THE A SITE IS NOW AVAILABLE TO THE tRNA THAT WILL BRING THE SECOND a.a.

27. ELONGATION
CODON RECOGNITION – THE CODON IN THE A SITE IS MATCHED BY THE INCOMING tRNA ANTICODON
PEPTIDE BOND FORMATION – THE INCOMING a.a. IN THE A SITE FORMS A PEPTIDE BOND WITH THE EXISTING CHAIN OF a.a. HELD IN THE P SITE
TRANSLOCATION – OCCURS WHEN tRNA IN THE A SITE IS MOVED TO THE P SITE, AND THE tRNA IN THE P SITE IS MOVED TO THE E SITE, WHERE IT IS RELEASED. THE A SITE IS CLEAR AND THE PROCESS RESTARTS

28. TERMINATION – A STOP CODON IN THE mRNA IS REACHED AND TRANSLATION STOPS
A PROTEIN CALLED RELEASE FACTOR BINDS TO STOP CODON AND THE POLYPEPTIDE IS FREED FROM THE RIBOSOME
POLYPEPTIDES FOLD TO ASSUME THEIR SPECIFIC CONFORMATION

31. CONCEPT 17.5
POINT MUTATIONS CAN AFFECT PROTEIN STRUCTURE AND FUNCTION

32. POINT MUTATIONS
ALTERATIONS OF JUST ONE BASE PAIR OF A GENE

33. BASE-PAIR SUBSTITUTION – REFERS TO THE REPLACEMENT OF ONE NUCLEOTIDE AND ITS COMPLEMENTARY BASE PAIR IN DNA WITH ANOTHER PAIR OF NUCLEOTIDES
MISSENSE MUTATIONS – SUBSTITUTIONS THAT ENABLE CODON TO STILL CODE FOR AN a.a. BUT IT MAY NOT BE THE CORRECT ONE
NONSENSE MUTATIONS – SUBSTITUTIONS THAT CHANGE A REGULAR a.a. CODON INTO A STOP CODON, CEASING TRANSLATION

34. FRAMESHIFT MUTATIONS
INSERTIONS OR DELETIONS – OF NUCLEOTIDE PAIRS IN A GENE
INTERFERE WITH CODON GROUPS AND CAUSE THE mRNA TO BE READ INCORRECTLY

36. MUTAGENS
SUBSTANCES OR FORCES THAT INTERACT WITH DNA IN WAYS THAT CAUSE MUTATIONS
EX. X-RAYS AND OTHER FORMS OF RADIATION, CHEMICALS