DNA: Master Programmer Stores genetic information Specifies primary structure of proteins Primary structure tertiary structure Tertiary structure protein function Control is indirect DNA uses RNA

Why RNA? Why does DNA need to transfer genetic information to RNA? DNA is found inside the nucleus. Ribosomes are outside the nucleus. DNA does not leave nucleus too large for nuclear pores protection of the original instructions. A way is needed to get genetic information from the DNA to the ribosomes to make proteins with amino acids. Special molecule, messenger RNA (mRNA), performs this task with codons.

RNA: The Other Code RNA and Protein Synthesis A.The Structure of RNA B. DNA and RNA Similarities/Differences C. Types of RNA D. Transcription/mRNA Synthesis E. Protein Synthesis/Translation

RNA Structure

RNA/DNA Similarities long chain made of nucleotides each nucleotide consists of: a sugar a phosphate a nitrogen base sugar and phosphate backbone

RNA/DNA Differences Different type of sugar (ribose) Single strand rather than a double strand RNA molecule is a disposable copy of DNA Nitrogen base THYMINE found in DNA replaced by a similar base URACIL (U) in RNA ex. ( A - U ) and ( C - G ) Three different types: Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)

Types of RNA Messenger RNA (mRNA) Is a complimentary copy of a DNA segment Single strand Contains codons which code for specific amino acids. Codons are triplet bases Manufactured in the nucleus

Other Types of RNA Ribosomal RNA (rRNA) makes up majority of ribosome made in the nucleolus Transfer RNA (tRNA) Carries amino acids to ribosome Single strand looped back on itself Anticodon-three nucleotides on tRNA are complementary to the three (codon) on the mRNA. Matching of anticodon (tRNA) to codon (mRNA) allows the correct amino acid to be put in place.

Transfer RNA Structure

Bring amino acids to ribosome Types of RNA: Summary RNA can be Messenger RNA Ribosomal RNA Transfer RNA also called which functions to also called which functions to also called which functions to mRNA Carry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome from to to make up DNA Ribosome Ribosomes

RNA Synthesis: Transcription Transcription- process by which one strand of DNA is copied to make a complementary strand of mRNA in the nucleus. A strand (Sense strand) of DNA serves as a pattern for mRNA. Enzymes “unzip” the two strands by breaking the hydrogen bonds. RNA polymerase, an enzyme, inserts appropriate nitrogen bases. Thymine (DNA) pairs with Adenine (RNA) Adenine (DNA) pairs with Uracil (RNA)

Transcription RNA polymerase DNA RNA Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA

RNA Synthesis: Transcription Transcription- process by which one strand of DNA is copied to make a complementary strand of mRNA in the nucleus. enzymes mRNA 5’C G G U A A C A U U A3’ DNA 3’G C C A T T G T A A T5’ enzymes DNA 5’C G G T A A C A T T A3’

RNA Synthesis: Transcription Three Stages: Initiation Attachment of RNA polymerase to DNA at promoter region Elongation Building of complimentary strand of RNA Termination Enzymes and transcript are released at terminator region

RNA Synthesis: Transcription Processing RNA Occurs in the nucleus Attachment of cap on 5’ end Methyl-guanine Helps in attachment to ribosomes Replacement of nucleotides on 3’ end 100-200 adenine tail Poly-A tail Determines life span of RNA Removal of introns RNA that doesn’t code for protein Splicing of exons Spliceosomes

DNA transcription by mRNA DNA transcription by mRNA. Coloured transmission electron micrograph of DNA & mRNA (messenger RNA) molecules forming a feather-like, transcriptionally-active structure. This DNA is from the nucleus of an amphibian egg. The backbone of the feather, running down the image, is a long strand of DNA coated with protein. Numerous mRNA molecules extend in clusters from the DNA strand. Transcription of genetic information begins at one end of the gene, with the mRNA molecules growing longer as they approach completion. Transcription is the first step in protein synthesis. Magnification: x6700 at 6x4.5cm size. http://www.sciencephoto.com/media/209651/enlarge

Transcription Transcription: http://www.youtube.com/watch?v=SMtWvDbfHLo&feature=relmfu * Transcription and Translation: http://www.youtube.com/watch?v=983lhh20rGY From DNA: the Secret of Life RNA Splicing http://www.youtube.com/watch?v=aVgwr0QpYNE * Translation: http://www.youtube.com/watch?v=TfYf_rPWUdY&feature=relmfu * Translation animation review: http://www.johnkyrk.com/DNAtranslation.html

Transmission electron micrograph of the first demonstration of an individual gene and its transcription product RNA. http://www.sciencephoto.com/media/210578/enlarge

Protein Synthesis A. Nucleotides in DNA have all the information to make proteins. B. DNA code copied into mRNA C. Proteins are made of amino acids which are coded from mRNA. D. mRNA code is read in a triplet form called a CODON which specifies certain amino acids using a decoder (p.237 BSCS Blue)

The Genetic Code Decoder: Amino Acid Chart BACK

Protein Synthesis: Translation Translation -the decoding of the mRNA code into proteins Only 20 amino acids make all life as we know it. How is this possible with only four nitrogen bases? Code is in triplets --64 combinations Codons on mRNA Anticodons on tRNA *AUG - codes for the amino acid methionine Initiator codon Always starts mRNA Is often removed after protein is synthesized *Some are “stop” codons Terminator codon

Translation Messenger RNA Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome mRNA Start codon

Translation B. Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. B. Nucleus Messenger RNA Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Methionine Ribosome mRNA Start codon

Translation (continued) The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. C. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Translation direction Ribosome

Translation (continued) The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain D. Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Ribosome tRNA Lysine tRNA mRNA mRNA Translation direction Ribosome

Translation DNA 3oT A C T T T G T A A C T5o enzymes mRNA 5oA U G A A A C A U U G A3o

polypeptide chain of amino acids mRNA rRNA

Protein Synthesis: Translation Same three stages as transcription Initiation, elongation, termination tRNA charging Attaching the correct amino acid to the tRNA Carried out by enzymes—one/amino acid Bonds amino acid to it’s respective tRNA Must be accurate for accurate protein synthesis Ribosome Sites P site—holds the tRNA and growing polypeptide chain Named for the peptide chain A Site—holds the next tRNA with the next amino acid Named for amino acid E Site—by the P Site, opposite the A Site Named for exit

Translation - Initiation

Translation - Initiation

Translation - Initiation

Translation - Elongation

Translation - Elongation

Translation - Elongation

Translation - Termination

Translation - Termination

Translation - Termination

Transport and Modification of Proteins Not all proteins are automatically functional Chemically modified Stabilized Cut into smaller segments Transported Vesicles Translated directly into Endoplasmic Reticulum Signal sequence

Translation Errors Errors do occur Misreading nucleotide sequence Initiation in wrong place Frameshift in reading frame (codon) Splicing mistakes introns/exons Changes in DNA Frameshift Stop codon Not enough of an amino acid

Translation Transcription and Translation: http://www.youtube.com/watch?v=erOP76_qLWA * http://www.youtube.com/watch?v=41_Ne5mS2ls from: DNA: The Secret of Life Translation: http://www.youtube.com/watch?v=TfYf_rPWUdY&feature=relmfu * https://www.youtube.com/watch?v=-zb6r1MMTkc Translation animation review: http://www.johnkyrk.com/DNAtranslation.html

Translation Transcription and Translation: http://207.207.4.198/pub/flash/26/transmenu_s.swf Translation animation review: http://www.johnkyrk.com/DNAtranslation.html