Both are nucleic acids… Be able to compare these two nucleic acids

DNA Monomer: Nucleotide 1 phosphate group 1 deoxyribose 5-carbon sugar 1 nitrogen-containing base (A, C, G, or T)

DNA polynucleotide Alternating sugar and phosphate molecules form backbone Nitrogenous bases form complementary pairs joined by hydrogen bonds Adenine (A) pairs with Thymine (T) Cytosine (C) pairs with Guanine (G)

DNA Bases

RNA Nucleotides 1 phosphate group 1 ribose sugar 1 nitrogenous base (A, C, G, or U) Uracil replaces thymine in RNA

Information Flow Genetic information in DNA is transcribed to RNA (transcription), then translated to protein (translation) The molecular basis of phenotypic traits are proteins that serve many different functions

Transcription & Translation of RNA Codons

One gene - One protein ? Each protein made at the ribosomes is controlled by a specific DNA gene (based on sequence of DNA base pairs) Changes in DNA base sequence can ultimately result in changes in the protein produced in cell

RNA Transcription DNA nucleotides are transcribed into RNA nucleotides in nucleus Adenine pairs with Uracil Cytosine pairs with Guanine Every 3 bases in DNA make 1 RNA triplet codon

RNA transcription RNA polymerase allows DNA nucleotides to be transcribed into RNA nucleotides and then links them together 3 different types of RNA are transcribed: 1.Messenger RNA (mRNA) 2.Transfer RNA (tRNA) 3.Ribosomal RNA (rRNA)

The Genetic Code 1961: The first RNA triplet codon was decoded and found to translate into a specific amino acid The genetic code is basically the same for all organisms, so bacterial cells can translate genetic messages from humans, and vice versa. Useful for Recombinant DNA technology

5’ 3’

Transcription of a Gene

At the ends of each intron are Small nuclear ribonucleoproteins or snRNP’s And these recognize splice sites Many snRNP’s join with protein = splicesome Ribozymes = RNA’s that function as enzymes Some intron RNA’s function as ribozymes to catalyze their own excision

Translation involves complex biochemistry! …Correct matches between tRNA and aa (aminoacyl-tRNA synthetase) …Correct match between tRNA anticodon and the mRNA codon …Ribosomes facilitate the coupling of tRNA anticodons with mRNA codons during protein synthesis …rRNA has three binding sites for tRNA …….A site = holds the tRNA carrying the next amino acid to be added to the growing polypeptide …….P site = holds the tRNA carrying the growing poly- peptide chain …….E site = exiting tRNA

Transfer RNA

Transfer RNA serve as “interpreters” during translation Each has an anticodon region that binds to specific codons on the messenger RNA Each also has an attachment site for an amino acid

EPA 5’ 3’ mRNA

A P E Initiation – mRNA, tRNA, aa 2 rRNA subunits Ribosome scans downstream 5’  3’ Elongation – aa are added one by one to the preceding aa mRNA is moved thru the ribosome in one direction only..5’ end first Ribosome and mRNA move relative to each other codon by codon Termination – stop codon reaches the A site of ribosome UAG, UAA, or UGA 5’ 3’ A U G U A C

E P A

E E E E P P P P A A A

Summary of transcription and translation E E E

Flow of genetic information DNA to RNA to protein Polyribosomes = many ribosomes read one mRNA Post-transcriptional Modificaiton –Coil and folding polypeptide –Modify aa by adding a sugar, lipid or phosphate group –Enzymes may remove one or more aa –Enzymes may cut protein in ½ –Free ribosomes = proteins function and dissolve in cytosol –Bound ribosomes = ER or Nuclear Membrane bound endomembrane system

RNA has many roles in a cell Point Mutations Substitutions Insertions/Deletions Mutagens What is a gene?

Sickle cell anemia: a single base mutation