Central Dogma DNA is the genetic material within the nucleus. Cytoplasm Nucleus DNA DNA is the genetic material within the nucleus. Replication The process of replication creates new copies of DNA. Transcription The process of transcription creates an RNA using DNA information. RNA Translation The process of translation creates a protein using RNA information. Protein

Transcription DNA is used as a template for creation of RNA using the enzyme RNA polymerase. DNA 5’ G T C A T T C G G 3’ 3’ C A G T A A G C C 5’

Transcription RNA polymerase reads the nucleotides on the template strand from 3’ to 5’ and creates an RNA Molecule in a 5’ to 3’ direction that looks like the coding strand. G T C A T T C G G C A G T A A G C C

Transcription The new RNA molecule is formed by incorporating nucleotides that are complementary to the template strand. DNA DNA coding strand 5’ G T C A T T C G G 3’ G RNA 5’ U C A 3’ 3’ C A G T A A G C C 5’ DNA template strand

Two types of nucleic acids DNA Usually double-stranded Has thymine as a base Deoxyribose as the sugar Carries RNA-encoding information Not catalytic RNA Usually single-stranded Has uracil as a base Ribose as the sugar Carries protein-encoding information Can be catalytic

Two types of nucleic acids # of strands kind of sugar bases used

rRNA is part of ribosome, used to translate mRNA into protein

tRNA is a connection between anticodon and amino acid

Initiation of transcription Transcription begins at the 3’ end of the gene in a region called the promoter. The promoter recruits TATA protein, a DNA binding protein, which in turn recruits other proteins. TATA binding protein Promoter Gene sequence to be transcribed TATA box DNA GG TATA CCC Transcription factor Transcription begins When a complete transcription complex is formed RNA polymerase binds and transcription begins.

10.10 Eukaryotic RNA is processed before leaving the nucleus Noncoding segments called introns are spliced out A cap and a tail are added to the ends to protect against degradation in the cytoplasm Exon Intron Exon Intron Exon DNA Transcription Addition of cap and tail Cap RNA transcript with cap and tail Introns removed Tail Exons spliced together mRNA Coding sequence NUCLEUS CYTOPLASM Figure 10.10

Fig. 10.20

10.8 The genetic code is the Rosetta stone of life Virtually all organisms share the same genetic code All organisms use the same 20 aa Each codon specifies a particular aa Figure 10.8A

10.8 The genetic code is the Rosetta stone of life Three codons do not code from an aa Rather they are found at the end of the coding sequence Tell a ribosome to stop translation and release the protein Figure 10.8A

Tryptophan and Methionine have only 1 codon each All the rest have more than one AUG has a dual function 3 stop codons that code for termination of protein synthesis Redundancy in the code but no ambiguity Figure 10.8A

Translation The process of reading the RNA sequence of an mRNA and creating the amino acid sequence of a protein is called translation. DNA T C A G template strand Transcription mRNA A G U C Messenger RNA Codon Translation Protein Lysine Serine Valine Polypeptide (amino acid sequence)

10.11 Transfer RNA molecules serve as interpreters during translation In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a polypeptide The process is aided by transfer RNAs Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Figure 10.11A

A codon of three nucleotides determines choice of amino acid

Translation is composed of three steps Initiation translation begins at start codon (AUG=methionine) Elongation the ribosome uses the tRNA anticodon to match codons to amino acids and adds those amino acids to the growing peptide chain Termination translation ends at the stop codon UAA, UAG or UGA

mRNA, a specific tRNA, and the ribosome subunits assemble during initiation Large Ribosomal subunit Initiator tRNA P site A site Start codon Small ribosomal subunit mRNA binding site 1 2 Figure 10.13B

Translation initiation Leader sequence Small ribosomal subunit mRNA 5’ 3’ A U G C Met U A C Initiator tRNA Assembling to begin translation

Translation Elongation Ribosome mRNA 5’ 3’ U C G A C U A C U P tRNA A Amino acid Met Gly Large ribosomal subunit

Translation Elongation C U A Met mRNA 5’ 3’ Gly G Cys A P

Translation Elongation mRNA 5’ 3’ U C G A A C Cys C U Lys C U P A Met Gly Lengthening polypeptide (amino acid chain)

Translation Elongation Stop codon mRNA 5’ U C G A U A C U Lys C U G Arg A C A P Met Gly Cys Release factor

Translation Termination Stop codon Ribosome reaches stop codon mRNA 5’ U C G A U A C U G Arg C U Release factor P Met Gly Cys Lys A

Translation Termination Once stop codon is reached, elements disassemble. U C G A C U G Release factor P Met Gly Cys Lys Arg A

Levels of protein structure Primary structure sequence of amino acids Secondary structure shapes formed with regions of the protein (helices, coil, sheets) Tertiary structure shape of entire folded protein due to interactions between particular peptides Quaternary structure structures formed by interaction of several proteins together e.g. Functional hemoglobin is two alpha-hemoglobin proteins and two beta-hemoglobin proteins

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Levels of protein structure

Misfolding of protein impairs function Misfolded prion protein disrupts functions of other normally folded prion proteins. Aberrant conformation can passed on propagating like an “infectious” agent.

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