The Ribosome Is part of the cellular machinery for translation, polypeptide synthesis Figure 17.1

Evidence from the Study of Metabolic Defects In 1909, British physician Archibald Garrod Was the first to suggest that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell

Nutritional Mutants in Neurospora: Scientific Inquiry Beadle and Tatum causes bread mold to mutate with X-rays Creating mutants that could not survive on minimal medium; each mutant was defective in a single gene supporting the one gene-one enzyme hypothesis

Overview: the roles of transcription and translation in the flow of genetic information No mRNA processing

Question: How does RNA (ribonucleic acid) differ from DNA (deoxyribonucleic acid)?

RNA DNA RNA ribose sugar Nitrogenous bases: single stranded uracil instead of thymine U : A C : G single stranded lots of RNAs mRNA, tRNA, rRNA transcription DNA RNA

The triplet code

The “Central Dogma” DNA RNA protein flow of genetic information within a cell transcription translation DNA RNA protein replication

The dictionary of the genetic code

The stages of transcription: initiation, elongation, and termination

The initiation of transcription at a eukaryotic promoter

RNA processing; addition of the 5 cap and poly(A) tail

RNA processing; addition of the 5 cap and poly(A) tail

The function of the cap is: prevent mRNA degradation by hydrolytic enzymes helps attach to the ribosome Function of the 3’ tail: same functions as the 5’cap also helps facilitate export of mRNA from nucleus

RNA processing: RNA splicing

The roles of snRNPs and spliceosomes in mRNA splicing

RNA Splicing Removes noncoding regions called introns snRNPs (small nuclear ribonucleoproteins) recognize the splicing signals that are at the ends of introns The RNA in the snRNP is called snRNA (small nuclear RNA) spliceosomes are the larger protein assemblies formed by the joining of snRNPs

Correspondence between exons and protein domains

The structure of transfer RNA (tRNA)

The structure of transfer RNA (tRNA)

Translation: the basic concept

An aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA

The anatomy of a functioning ribosome

The initiation of translation

The elongation cycle of translation

The termination of translation

Peptide Bonds Join Amino Acids

Polyribosomes

Coupled transcription and translation in bacteria

The signal mechanism for targeting proteins to the ER

The polypeptides of proteins destined for the endomembrane system are marked by a signal peptide, which targets the protein to the ER. A signal recognition particle (SRP) functions as an adaptor that brings the ribosome to a receptor protein built into the ER membrane.

Mutations – a change in the genetic material; most are neutral and have little effect on expression of genes.

Point Mutations – occur at a single point in a DNA sequence A Frameshift Mutation changes the “reading frame” of the genetic message.

Categories and Consequences of Point Mutations: Base-Pair Substitution

The molecular basis of sickle-cell disease: a point mutation

The Primary Structure of a Protein

Categories and consequences of point mutations: Base-pair insertion or deletion

A summary of transcription and translation in a eukaryotic cell

The ___________ on tRNA is complementary to the ___________ on mRNA.

Distinguish between a frameshift mutation and a point mutation. How could a Frameshift Mutation lead to Missense or Nonsense codons?

Protein Synthesis Animations:   http://bcs.whfreeman.com/hillis1e/#667501__674148__ DNA and RNA Structure: http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html# http://highered.mcgraw-hill.com/olc/dl/120077/micro06.swf Processing of Gene Information (Prokaryotes vs Eukaryotes): http://highered.mcgraw-hill.com/olc/dl/120077/bio25.swf RNA Splicing: http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/rna_splicing.html How Splicesomes Process RNA: http://highered.mcgraw-hill.com/olc/dl/120077/bio30.swf Transcription: http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/mrna_synthesis__transcription_.html http://bcs.whfreeman.com/thelifewire/content/chp12/1202001.html http://www.biologyalive.com/life/classes/apbiology/documents/Unit%209/17_Lectures_PPT/media/17_07TranscriptionIntro_A.swf http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/stages_of_transcription.html Translation: http://sites.fas.harvard.edu/~biotext/animations/TRANSLATE20b.swf http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/how_translation_works.html Translation Elongation: http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/translation_elongation.html Translation Termination: http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter15/translation_termination.html

What is the difference between a mutagen and a carcinogen? What is the role of the signal-recognition particle?

Distinguish between the roles of each of the three sites located within the ribosome.

List three major differences between the transcription process in prokaryotes vs. eukaryotes.

Every three bases on mRNA is called a/an _______ and codes for If a DNA sequence reads A-T-T-C-G-C what are the complementary mRNA and tRNA sequences? RNA Polymerase attaches to the DNA strand and starts reading the bases at an area called the: Every three bases on mRNA is called a/an _______ and codes for a specific __________ __________.

Transcription DNA mRNA A U T A G C C G Translation mRNA tRNA A U U A G C C G

Transcription takes place in the _______ of the cell when mRNA copies the _____ strand. Translation takes place in the _______ of the cell when tRNA copies the _______ strand at the __________.