1. 1 The Central Dogma of Molecular Biology Mark Mayo Cypress College Last update 3/11/14

2. 2 The Central Dogma of Molecular Biology Reverse Transcription

3. 3 Importance of Proteins There are three main kinds: There are three main kinds: structural - make up most body parts structural - make up most body parts hormone - chemical that controls the body hormone - chemical that controls the body enzyme - catalyst - speeds up chemical reactions enzyme - catalyst - speeds up chemical reactions Insulin, a protein

4. 4 Importance of Proteins Without proteins there would be no life Without proteins there would be no life All cells make proteins All cells make proteins Proteins in your body make up your: Proteins in your body make up your: Hair Hair Nails Nails Muscles Muscles Skin Skin Cartilage Cartilage

5. 5 Discovery of DNA (deoxyribonucleic acid) 1953 Watson, Crick and Wilkins determined the structure of DNA to be a double helix 1953 Watson, Crick and Wilkins determined the structure of DNA to be a double helix They won a Nobel Prize for their work They won a Nobel Prize for their work

6. 6 Structure of the DNA molecule DNA is shaped like a double helix DNA is shaped like a double helix It is like a spiral staircase It is like a spiral staircase Another way to think of it is a twisted ladder Another way to think of it is a twisted ladder

7. 7 Connecting the DNA molecule Rails* of the DNA ladder are alternating sugar & phosphates Rails* of the DNA ladder are alternating sugar & phosphates Rungs* are composed of pairs of bases Rungs* are composed of pairs of bases A bonds with T* A bonds with T* G bonds with C* G bonds with C*

8. 8 Connecting the DNA Molecule The DNA Ladder* The DNA Ladder* P S – A P S – T P S – G P S - C P T - S P A - S P C - S P G - S P S – A P S – T P ? – G P S - C P T - ? P ? - S P C - S P G - S * * *

9. 9 Connecting the DNA molecule The two strands of DNA are different The two strands of DNA are different One is called the sense strand and it is the plan to make a protein One is called the sense strand and it is the plan to make a protein The other strand is the antisense strand and it is only used for protection of the sense strand The other strand is the antisense strand and it is only used for protection of the sense strand

10. 10 Connecting the DNA molecule The two strands of DNA are said to be antiparallel* The two strands of DNA are said to be antiparallel* One strand is oriented in a 5’ to 3’ direction* One strand is oriented in a 5’ to 3’ direction* The other strand is oriented in the opposite 3’ to 5’ direction* The other strand is oriented in the opposite 3’ to 5’ direction* 5’ 3’ 3’ 5’ sense antisense

11. 11 Connecting the DNA molecule Nucleotides are units composed of a base, phosphate and a sugar Nucleotides are units composed of a base, phosphate and a sugar

12. 12 Connecting the DNA molecule The two strands of DNA bases are connected by weak forces called hydrogen bonds* The two strands of DNA bases are connected by weak forces called hydrogen bonds* 2 hydrogen bonds 3 hydrogen bonds * *

13. 13 Components of DNA Phosphate Phosphate

14. 14 Components of DNA Deoxyribose (sugar) Deoxyribose (sugar)

15. 15 Components of DNA DNA bases (4 different types) DNA bases (4 different types) Adenine Adenine Thymine* Thymine* Guanine Guanine Cytosine Cytosine

16. 16 Components of DNA Proteins are attached to the DNA helix in cells Proteins are attached to the DNA helix in cells These proteins are known as histones These proteins are known as histones They assist in DNA storage They assist in DNA storage

17. 17 DNA and RNA Compared DNA DNA Found only in nucleus * Found only in nucleus * Double stranded helix Double stranded helix Bases = ATGC * Bases = ATGC * Sugar = Deoxyribose Sugar = Deoxyribose RNA RNA Found in ribosomes, nucleolus * Single stranded helix * Bases = AUGC (URACIL) * Sugar = Ribose * DNA is also found in a select number of other organelles

18. 18 Replication of DNA Replication - the making of an exact copy of the DNA molecule Replication - the making of an exact copy of the DNA molecule Replication occurs whenever a cell divides Replication occurs whenever a cell divides The copy must be 100% accurate (errors = death possibly) The copy must be 100% accurate (errors = death possibly) Replication practice (find the complimentary bases or base sequence) * Replication practice (find the complimentary bases or base sequence) * A – pairs with ? A – pairs with ? T – pairs with ? T – pairs with ? G – pairs with ? G – pairs with ? C – pairs with ? C – pairs with ?

19. 19 Replication of DNA

20. 20 Stages in replication (basic) DNA molecule is split in two at the end by the work of enzymes * DNA molecule is split in two at the end by the work of enzymes * DNA unzips slightly and the two strands unwind * DNA unzips slightly and the two strands unwind * new nucleotides attach to the free ends * ( A-T, G-C) new nucleotides attach to the free ends * ( A-T, G-C) more DNA unzips more DNA unzips more nucleotides attach * more nucleotides attach * process continues until completed process continues until completed result is two (2) double strands of DNA result is two (2) double strands of DNA each strand is 50% new and 50% old DNA each strand is 50% new and 50% old DNA

21. 21 Stages in replication DNA replication is different on the leading and lagging strands * DNA replication is different on the leading and lagging strands * Lagging strand has Okazaki fragments* Lagging strand has Okazaki fragments* *

22. 22 Stages in replication DNA replication is different on the leading and lagging strands * DNA replication is different on the leading and lagging strands * *

23. 23 Enzymes * Involved in DNA Replication DNA polymerase – adds nucleotides in a 5’ to 3’ direction DNA polymerase – adds nucleotides in a 5’ to 3’ direction Topoisomerase Topoisomerase Gyrase Gyrase RNA primase RNA primase DNA ligase – connects the gaps in the lagging strand DNA ligase – connects the gaps in the lagging strand

24. 24 DNA Replication in Motion

25. 25 Introns and Exons Introns – sequences in the DNA that are NOT used to make mRNA or to make a protein. They are NOT transcribed * Introns – sequences in the DNA that are NOT used to make mRNA or to make a protein. They are NOT transcribed * Exons – sequences in the DNA that are expressed or used to make mRNA and ultimately are used to make a protein Exons – sequences in the DNA that are expressed or used to make mRNA and ultimately are used to make a protein

26. 26 Introns and Exons

27. 27 Restriction Enzymes Restriction enzymes (also known as restriction endonucleases) recognize specific DNA sequences and CLEAVE or cut the DNA into pieces * Restriction enzymes (also known as restriction endonucleases) recognize specific DNA sequences and CLEAVE or cut the DNA into pieces * Generally these cuts occur in a manner which leaves a sticky end of single strand DNA Generally these cuts occur in a manner which leaves a sticky end of single strand DNA These pieces can be separated by using gel electrophoresis (this is like electronic chromatography) These pieces can be separated by using gel electrophoresis (this is like electronic chromatography) We use restriction enzymes for cutting bacterial, viral or even human DNA and later insertion of the desired DNA fragments – called gene splicing * We use restriction enzymes for cutting bacterial, viral or even human DNA and later insertion of the desired DNA fragments – called gene splicing *

28. 28 Restriction Enzymes sticky ends blunt ends

29. 29 Restriction Enzymes

30. 30 Ribonucleic Acid (RNA) Three types of RNA: Three types of RNA: rRNA = ribosomal RNA - makes up the ribosome rRNA = ribosomal RNA - makes up the ribosome mRNA = messenger RNA - is the message from DNA for the construction of the new protein molecule * mRNA = messenger RNA - is the message from DNA for the construction of the new protein molecule * tRNA = transfer RNA - carries amino acids to ribosomes tRNA = transfer RNA - carries amino acids to ribosomes

31. 31 Ribonucleic Acid (RNA) Ribosomal RNA is used to make a ribosome Ribosomal RNA is used to make a ribosome The ribosome “reads” the mRNA plan for the new protein The ribosome “reads” the mRNA plan for the new protein mRNA is the set of directions for a new protein* mRNA is the set of directions for a new protein* Ribosome

32. 32 Ribonucleic Acid (RNA) Messenger RNA Messenger RNA Sense Antisense

33. 33 Ribonucleic Acid (RNA) Transfer RNA Transfer RNA Each tRNA holds one amino acid Each tRNA holds one amino acid Every tRNA has a special region called the anti-codon (3 bases) Every tRNA has a special region called the anti-codon (3 bases) An tRNA anti-codon "mates" with codon on the mRNA molecule An tRNA anti-codon "mates" with codon on the mRNA molecule There are 61 different tRNA molecules, yet only about 20 amino acids (hint: 3 stop codons) There are 61 different tRNA molecules, yet only about 20 amino acids (hint: 3 stop codons)

34. 34 Ribonucleic Acid (RNA) Transfer RNA Transfer RNA

35. 35 Transcription Transcription is the special copying of one side of the DNA molecule (the sense strand) that results in the production of a single strand of RNA * Transcription is the special copying of one side of the DNA molecule (the sense strand) that results in the production of a single strand of RNA * The original DNA is not changed The original DNA is not changed This process can be repeated This process can be repeated The amount of DNA that is transcribed is usually one gene The amount of DNA that is transcribed is usually one gene The r in the title is red to remind you that transcription makes RNA

36. 36 Transcription Process of Transcription Process of Transcription DNA is unzipped by an enzyme DNA is unzipped by an enzyme Only one side fills with RNA nucleotides by the action of another enzyme RNA polymerase A-U, G-C (NO THYMINE = T) Only one side fills with RNA nucleotides by the action of another enzyme RNA polymerase A-U, G-C (NO THYMINE = T) As the RNA strand separates the DNA strands reattach as before the process started As the RNA strand separates the DNA strands reattach as before the process started 4. The result is the original DNA plus a new RNA strand 4. The result is the original DNA plus a new RNA strand

37. 37 Transcription

38. 38 Transcription Uracil – a base only found in RNA Uracil – a base only found in RNA

39. 39 Transcription Transcription Practice * Transcription Practice * A (in DNA) pairs with ___ in RNA A (in DNA) pairs with ___ in RNA T (in DNA) pairs with ___ in RNA T (in DNA) pairs with ___ in RNA G (in DNA) pairs with ___ in RNA G (in DNA) pairs with ___ in RNA C (in DNA) pairs with ___ in RNA C (in DNA) pairs with ___ in RNA

40. 40 Transcription

41. 41 Transcription * Sometimes two or more ribosomes attach to the mRNA transcript at the same time and this is called a polysome *

42. 42 Translation Translation * is the reading of the RNA code, by ribosomes, to make proteins * or polypeptides Translation * is the reading of the RNA code, by ribosomes, to make proteins * or polypeptides Translation is often called protein synthesis Translation is often called protein synthesis *

43. 43 Translation mRNA is the message (the plan for the protein) mRNA is the message (the plan for the protein) rRNA "reads" the mRNA (the ribosome) * rRNA "reads" the mRNA (the ribosome) * tRNA molecules carry amino acids to the ribosome for assembly into proteins tRNA molecules carry amino acids to the ribosome for assembly into proteins The ribosome allows only the correct tRNA to add its amino acid – others are rejected The ribosome allows only the correct tRNA to add its amino acid – others are rejected

44. 44 Translation * * * * Anticodons * * Codons *

45. 45 Translation

46. 46 Translation Triplet codons - groups of three bases on mRNA that code for specific amino acids * Triplet codons - groups of three bases on mRNA that code for specific amino acids *

47. 47 Translation The function of special stop codons is to terminate* or end the translation process* The function of special stop codons is to terminate* or end the translation process* The stop codons are: UAA, UAG and UGA The stop codons are: UAA, UAG and UGA The function of the start codon is to serve as a place for the ribosome to begin translation The function of the start codon is to serve as a place for the ribosome to begin translation The only start codon is AUG The only start codon is AUG

48. 48 Translation 9 bases would give __?__ amino acids * 9 bases would give __?__ amino acids * 27 bases would give __?__ amino acids * 27 bases would give __?__ amino acids *

49. 49 Translation Anticodon practice * Anticodon practice * codonanticodon AAAUUU CCC ? UUU ? UCG ? NEVER look up the anticodon in the chart or table! Look the CODON in the table or chart

50. 50 Translation

51. 51 Central Dogma Practice Antisense DNA Sense DNA mRNA Protein A T G G G G C C C T T T A A A G G C T A A First you R E P L I C A T E the top line of DNA using the DNA bases A T G C

52. 52 Central Dogma Practice Antisense DNA Sense DNA mRNA Protein A T G G G G C C C T T T A A A G G C T A A T A C C C C G G G A A A T T T C C G A T T Second you T R A N S C R I B E the second line of DNA (sense DNA) using the RNA bases A U G C NO T’s

53. 53 Central Dogma Practice Antisense DNA Sense DNA mRNA Protein A T G G G G C C C T T T A A A G G C T A A T A C C C C G G G A A A T T T C C G A T T A U G G G G C C C U U U A A A G G C U A A Lastly, you T R A N S L A T E the mRNA line using the chart and find out the amino acids, Start and Stop

54. 54 Central Dogma Practice Antisense DNA Sense DNA mRNA Protein A T G G G G C C C T T T A A A G G C T A A T A C C C C G G G A A A U U U C C G A T T A U G G G G C C C U U U A A A G G C U A A Start Glycine Proline Phenylal. Lysine Glycine Stop Proteins are made up of a string or amino acids Answers Central Dogma Practice