2. Introduction to Central Dogma: DNA Replication, Transcription and Translation

3. What is Central Dogma? It is the flow of genetic information from DNA to Proteins Transcription Translation DNA mRNA Proteins Replication DNA

4. What is DNA? It is the fascinating molecule that contains the Code of Life.

5. It is the Genetic Code, which is the set of “messages” that are “translated” by ribosomes into proteins that define YOU What Is the Code of Life?

6. Recall that DNA and RNA belong to the class of biomolecules called Nucleic Acids, which are made up of nucleotide monomers Structure of Nucleic Acids

7.  The nucleotide subunits consist of: 1. A Nitrogen Base 2. A Sugar (either Deoxyribose or Ribose) 3. A Phosphate Group Structure of Nucleotides

8. Nitrogen Bases Can Be: Adenine Guanine Cytosine Thymine (only DNA) Uracil (only RNA) Nitrogen Bases A G C T U

9.  Erwin Chargaff analyzed DNA from different organisms and found that A = T & G = C Chargaff’s Rule of Base Pairing According to Chargaff, in DNA: A always bonds with T G always bonds with C

10. Image by: Riedell The Sugar Group Can Be Either: Deoxyribose (in DNA) or- Ribose (in RNA) The Sugar Group

11.  Purines consist of Adenine and Guanine bases; they are double-ring structures  Pyrimidines consist of Thymine and Guanine bases; they are single-ring structures  A Purine ALWAYS bonds with a Pyrimidine….A with T and G with C Purines & Pyrimidines

12. DNA has no URACIL RNA has no THYMINE Nitrogen Base Difference DNA & RNA

13. The nitrogen bases are held together by weak hydrogen bonds The sugar and phosphate groups are held together by strong covalent phosphodiester bonds Bonding in DNA Covalent Phosphodiester Bonds

14. Semi-Conservative : Strand separation, followed by copying of each strand. Each separated strand acts as a template for the synthesis of a new complementary strand. DNA Replication (occurs in the nucleus)

15. Step 1 : Unwinding of the double helix  Helicase enzyme unwinds the double helix & creates a replication fork DNA Replication (occurs in the nucleus)

16. Step 2 : One DNA strand is used as a template to create the new copy DNA DNA A – T G – C C – G A – T A – T etc DNA Replication (occurs in the nucleus)

17. Transcription produces genetic messages in the form of mRNA DNA Transcription (occurs in the nucleus) DNA Template mRNA

18. STEP 1: As in replication, the DNA double helix unzips STEP 2: RNA nucleotides line up along one strand of DNA, following the base-pairing rules DNA Transcription (occurs in the nucleus) DNA Template mRNA

19. STEP 3: DNA is transcribed into RNA DNA mRNA G C T A AU G G G C T A DNA Transcription (occurs in the nucleus) DNA Template mRNA

20. Single-stranded mRNA peels away from DNA and prepares to move into the cytoplasm DNA Transcription (occurs in the nucleus) DNA mRNA Nucleus Cytoplasm

21. Eukaryotic RNA is processed before leaving the nucleus  The non-coding segments, called introns, are spliced out  A cap & tail are added to the ends DNA Transcription (occurs in the nucleus) Exon Intron Introns removed Exons spliced together Coding sequence mRNA DNA RNA transcript with cap and tail Transcription Addition of cap and tail NUCLEUS CYTOPLASM Cap Tail

22. mRNA leaves the nucleus and moves into the cytoplasm where it will be “translated” into a polypeptide (a fancy word for a protein) DNA Translation (occurs in the cytoplasm) TRANSCRIPTION TRANSLATION PROTEIN CYTOPLASM NUCLEUS

23. The words that will be translated are triplets of mRNA bases called codons The codons in a gene determine the amino acids in the polypeptide sequence DNA Translation (occurs in the cytoplasm) DNA molecule DNA strand TRANSCRIPTION RNA TRANSLATION Polypeptide Amino acid Gene 1 Gene 2 Gene 3 Codon

24. In the cytoplasm, a ribosome attaches to the mRNA A tRNA pairs with each codon, adding an amino acid to the growing polypeptide DNA Translation (occurs in the cytoplasm)

25. UCAG U C A G G A C U G A C U G A C U G A C U UUUUUU UUCUUC UUAUUA UUGUUG CUUCUU CUCCUC CUACUA CUGCUG AUUAUU AUCAUC AUAAUA AUGAUG GUUGUU GUCGUC GUAGUA GUGGUG phe leu ile met (start) val UCUUCU UCCUCC UCAUCA UCGUCG CCUCCU CCCCCC CCACCA CCGCCG ACUACU ACCACC ACAACA ACGACG GCUGCU GCCGCC GCAGCA GCGGCG ser pro thr ala UAUUAU UACUAC UAAUAA UAGUAG CAUCAU CACCAC CAACAA CAGCAG AAUAAU AACAAC AAGAAG AAAAAA GAUGAU GACGAC GAAGAA GAGGAG tyr stop his gln asn lys asp glu UGUUGU UGCUGC UGAUGA UGGUGG CGUCGU CGCCGC CGACGA CGGCGG AGUAGU AGCAGC AGAAGA AGGAGG GGUGGU GGCGGC GGAGGA GGGGGG cys stop trp arg ser arg gly First Base Third Base Second Base mRNA Genetic Code Chart

26. Table 14.2 Types of RNA Type of RNA Functions inFunction Messenger RNA (mRNA) Nucleus, migrates to ribosomes in cytoplasm Carries DNA sequence information to ribosomes Transfer RNA (tRNA) Cytoplasm Provides linkage between mRNA and amino acids; transfers amino acids to ribosomes Ribosomal RNA (rRNA) Cytoplasm Structural component of ribosomes

27. Mutations are changes in the DNA base sequence  Are caused by errors in DNA replication  Are caused by environmental factors, such as exposure to radiation and chemicals or temperature changes Mutations most likely cause altered proteins to be produced 2 Kinds of Mutations: Gene Mutations & Chromosomal Mutations Mutations

28. Point mutations – changes of a single DNA nucleotide – can cause sickle-cell anemia and many other disorders Gene Mutations Normal hemoglobin DNAMutant hemoglobin DNA mRNA Normal hemoglobinSickle-cell hemoglobin Glu Val

29. Types of Point mutations  Substitutions  Insertions  Deletions Gene Mutations

30. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings mRNA NORMAL GENE BASE SUBSTITUTION BASE DELETION ProteinMetLysPheGlyAla MetLysPheSerAla MetLysLeuAlaHis Missing Gene Mutations

31. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Deletion Duplication Inversion Homologous chromosomes Reciprocal translocation Non-homologous chromosomes Chromosomal Mutations

32. Human karyotype showing addition of 1 chromosome on autosome 21 – Down Syndrome Chromosomal Mutations Chromosome painting