DNA Replication, Transcription, & Translation Nestor T. Hilvano, M.D., M.P.H. (Images Copyright Discover Biology, 5th ed., Singh-Cundy and Cain, Textbook, 2012.)

Learning Objectives Define key terminologies. DNA replication, transcription, translation, codon, anticodon, introns, exons, and nucleotide Compare the structure of DNA and RNA and its functions. Describe the process of DNA replication. Describe the locations, reactants, and products of transcription. Describe the locations, reactants, and products of translation. Describe major types of mutations and their possible consequences.

Wordstem co- together liga- bound or tied pleio- more poly- many centesis- a puncture

DNA Discovery Rosalind Franklin (1950)- diffracted helical shape of DNA when performing X-ray crystallography using samples of uniformly oriented strands created by Maurice Wilkins Watson (U.S.) and Crick (Great Britain)- used quantum mechanics and x-ray crystallography (Wilkin and Franklin) to determine DNA structure; double helix model; won the Nobel Prize in medicine Rosalind Franklin: July 25, 1920 – April 16, 1958

Figure 14.3 The DNA Double Helix and Its Building Blocks A nucleotide consists of three types of chemical groups: a phosphate, a sugar, and a nitrogen-containing base. DNA contains four types of nucleotides, varying only in the type of base found in them. DNA consists of two complementary strands of nucleotides that are twisted into a spiral around an imaginary axis, rather like the winding of a spiral staircase. The two strands are held together by hydrogen bonds between their complementary bases. (Inset) James Watson (left) and Francis Crick, with a model of the DNA double helix.

5 end 3 end P HO A T C G OH 5 4 3 2 1 1 Figure 10.5B Figure 10.5B The opposite orientations of DNA strands 6

DNA Replication Semiconservative; DNA unwound into 2 template strands New base pairs (complimentary base pairing) Adding at the end of 3’ end of the template toward the 5’ end (leading strand) or at 5’ end toward the 3’ end (lagging strand= okazaki fragments) DNA polymerase and DNA ligase

Figure 14.5 The Replication of DNA Is Semiconservative In this overview of DNA replication, the template DNA strands are blue, and the newly synthesized strands are orange. One strand (blue) from the parent double helix is conserved in each newly made daughter double helix (blue and orange).

. helicase-unwinds DNA, req. ATP b. single-stranded binding proteins-keep DNA from rebinding to self c. origin of replication (1 in proks, multi in euks) d. primase-synthesiaex RNA primer-short strand-where DNA polymerase attaches to strand e. DNA polymerase III-open right hand: palm = active site; fingers = recognize bases f. DNA polymerase I-knocks off RNA/makes DNA (lagging strand) g. DNA ligase-makes phosphodiester bond-joins sugar phosphate backbone together at gaps (lagging strand) Build-new DNA built off of template 3` end toward 5` end-only one strand has this orientation = leading strand other strand = lagging strand= thread thru, add primer and work back toward earlier primer-okazaki fragments

Flow of Genetic Information from DNA to RNA to Protein Organism’s genotype – is carried in its sequence of bases triplet (ex. TAC) Transcription is= DNA to mRNA Translation is = mRNA to protein (polypeptide) Codon – triplets of bases found in mRNA (ex. AUG), which determines A.A. sequence on a polypeptide, 64 possible codons - 61 code for amino acids - start codon= AUG (Methionine) - 3 stop codons = UAG, UGA, UAA

Figure 15.5 The 64 Possible Codons Specify Amino Acids or Signals That Start or Stop Translation

Figure 15.2 Genetic Information Flows from DNA to RNA to Protein during Transcription and Translation The transcription of a protein-coding gene produces an mRNA molecule, which is then transported to the cytoplasm, where translation occurs and the protein is made with the help of ribosomes. Different amino acids in the protein being constructed at the ribosome are represented here by different colors and shapes.

Transcription What is transcription? RNA polymerase RNA splicing – introns (nonsense), exons (sense) Given a DNA template of TACCGC. What is the corresponding codon in mRNA transcribed? _________________ RNA polymerase DNA of gene Promoter DNA Terminator Area shown In Figure 10.9A Growing RNA Completed RNA polymerase initiation elongation termination Exon Intron Exon Intron Exon DNA Cap Transcription Addition of cap and tail RNA transcript with cap and tail Introns removed Tail Exons spliced together mRNA Coding sequence Nucleus Cytoplasm

DNA Transcription RNA Codon Translation Polypeptide Amino acid A A A C Figure 10.7_1 DNA A A A C C G G C A A A A Transcription U U U G G C C G U U U U RNA Codon Translation Figure 10.7_1 Transcription and translation of codons (partial) Polypeptide Amino acid 14

Figure 15.3 RNA Polymerase Transcribes DNA-Based Information into RNA-Based Information

Translation Ribosome attaches to mRNA tRNA (anticodon)- interprets the message; delivers amino acids specified by mRNA codons * 3 stages – initiation, elongation, termination * Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation Met Initiator tRNA 1 2 mRNA Small ribosomal subunit Start codon Large ribosomal subunit A site U A C A U G P site Figure 10.13B

Figure 15.7 Transfer RNA Delivers Amino Acids Specified by mRNA Codons A space-filling-model (left) and a diagrammatic version (right) illustrate the general structure of all tRNA molecules. Similar regions in the space-filling model and on the diagram are shown in matching colors. Each tRNA carries a specific amino acid (serine in this example) and has a specific anticodon sequence (UCG in this example) that binds to a complementary three-base sequence (the codon) in the mRNA.

*anti-codon end- pairs with codon on mRNA *amino acid on 3` end Fig. 17-14 3 tRNA: *anti-codon end- pairs with codon on mRNA *amino acid on 3` end * clover leaf shape base pairs Amino acid attachment site 5 Hydrogen bonds Anticodon (a) Two-dimensional structure 5 Amino acid attachment site 3 Figure 17.14 The structure of transfer RNA (tRNA) Hydrogen bonds 3 5 Anticodon Anticodon (c) Symbol used in this book (b) Three-dimensional structure

(b) Schematic model showing binding sites Fig. 17-16b P site (Peptidyl-tRNA binding site) A site (Aminoacyl- tRNA binding site) E site (Exit site) E P A Large subunit mRNA binding site Small subunit (b) Schematic model showing binding sites Growing polypeptide Amino end Next amino acid to be added to polypeptide chain Figure 17.16 The anatomy of a functioning ribosome E tRNA mRNA 3 Codons 5 (c) Schematic model with mRNA and tRNA

Figure 15.8 (Part 1) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

Figure 15.8 (Part 2) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

Figure 15.8 (Part 4) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

http://www. youtube. com/watch http://www.youtube.com/watch?v=4PKjF7OumYo&feature=related (go to 4:36) http://www.youtube.com/watch?v=5bLEDd-PSTQ&feature=related Figure 15.8 (Part 5) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

Mutation Change in the nucleotide sequence of DNA; somatic (body cells; passed on during cell division); germ-line (during gametes development; passed on to offspring) Caused by errors in DNA replication or recombination, or by mutagens Point mutation- changes in one base pair of genes (1 gene); substitution, insertion, or deletion Chromosomal mutation- entire section of chromosome, affects multiple genes; caused by free radicals breaking sugar-phosphate bonds, UC radiation, and chemical affecting structure of bases. C T A Normal hemoglobin Mutant hemoglobin DNA G U Sickle-cell hemoglobin Normal hemoglobin DNA Glu Val mRNA Figure 10.16A

Point Mutation Can results to: silent- no change/effect due to redundancy Mis-sense- change of one A.A. (different A.A. sequence); low efficiency Non-sense- lead to change one A.A. to stop codon; polypeptide synthesis stop, non-functional protein Frameshift (insertion or deletion)- entire 3 base codon affected; major difference causing non-functional proteins

Figure 15.9 A Change in the DNA Sequence Translates into a Change in the Amino Acid Sequence of the Protein Two kinds of mutations are shown here: a substitution and an insertion. In each case, the mutation and its effects on transcription and translation are shown in red.

Figure 15.10 Mutations in a Single Base in the Hemoglobin Gene Can Lead to Sickle-Cell Anemia

Nucleotide substitution Figure 10.16B Normal gene A U G A A G U U U G G C G C A mRNA Protein Met Lys Phe Gly Ala Nucleotide substitution A U G A A G U U U A G C G C A Met Lys Phe Ser Ala U Deleted Nucleotide deletion A U G A A G U U G G C G C A U Figure 10.16B Types of mutations and their effects Met Lys Leu Ala His Inserted Nucleotide insertion A U G A A G U U G U G G C G C Met Lys Leu Ala His 28

Homework Define terms: nucleotide, translation, transcription, DNA replication, introns, exons, codons, anticodons, mutation, point mutation, chromosomal mutation. Describe the 3 types of RNA: mRNA, tRNA, and rRNA. Give the bases of CATAAG DNA template, what is the corresponding bases in DNA replication? Given the above DNA template in #3 question, what is the corresponding codons (mRNA) in transcription? Given AGG codon (mRNA), what is the corresponding anti-codon (tRNA) in translation? Describe types of point mutation.