1. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies DNA: The Genetic Material Chapter 14 Copyright © McGraw-Hill Companies Permission required for reproduction or display

2. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Hammerling Experiment  Cells of green alga cut into pieces and observed to see which were able to express heredity information. - Discovered heredity information stored in the foot of the cell (nucleus location) because the foot was needed to regenerate the cap and stalk.

3. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.2

4. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Transformation Experiments Mendel discovered chromosomes are composed of proteins and DNA. But it took several experiments to conclusively determine specifically which substance made up genes.  Griffith Experiment - Documented movement of genes from one organism to another (transformation).

5. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Griffith Experiment 1. Used a strain of strep bacteria 2. The polysaccharide coat on this bacteria makes it virulent. 3. The DNA specifying the toxic coat had passed from the dead virulent bacteria to the live, coat-less bacteria, making them virulent (transformation).

6. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.4

7. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Transformation The receiving bacteria must be in a state of “competence” (high cell density and or nutritional limitation). Some cells release their DNA upon death to be taken up by other cells. Transformation can occur by: 1. Conjugation : transfer of genetic material between two bacterial cells in direct contact 2. Transduction: injection of foreign DNA by a bacteriophage virus into the host bacterium

8. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Avery and Hershey-Chase Experiments Avery Experiment  Removed almost all protein from bacteria, and found no reduction in transforming activity. Concluded that DNA is the hereditary material, not the proteins. Hershey-Chase  Used radioactive isotopes to label DNA and protein. Found genes used to specify new generations of viruses were made of DNA because radioactive DNA was found in the bacteria (from bacteriophage injection) and protein with tracer was not in the bacteria.

9. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.5

10. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies DNA Discovered by Fredrich Miescher in 1869 Originally called nuclein (nucleus) that he extracted from human cells and fish sperm The nitrogen and phosphorous proportions were different enough from any other substance in a cell and the DNA is slightly acidic, so name became nucleic acid

11. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Chemical Nature of Nucleic Acids DNA made up of nucleic acids.  Five carbon sugar, phosphate group, and an organic base. - Purines - Large bases  Adenine and Guanine - Pyrimidines - Small bases  Cytosine and Thymine  Chargaff’s Rule - A =T and G=C Nucleotides are distinguished by the bases

12. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.6

13. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Numbering Of Nucleotide Carbons To ID the various chemical groups in DNA it is customary to number the carbon atoms of the sugar and then refer to any chemical group attached to a carbon atom by that number (1-5). Carbons are numbered clockwise from the oxygen. The primary symbol(‘) means that it refers to a carbon in sugar, not in a base.

14. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.7

15. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Structure of a Nucleotide The phosphate group is attached to the 5’ carbon of the sugar. The base is attached to the 1’ carbon of the sugar. A free hydroxyl group is (OH-) is attached to the 3’ carbon. Remember…..the hydroxyl group is a functional group that makes C-H cores of molecules (like nucleotides) polar for bonding and solubility

16. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Chemical Nature of Nucleic Acids Nucleotide made up of a sugar attached to a phosphate and a base. The chemical reaction of the 5’ phosphate of one nucleotide and the 3’ hydroxyl group of another allows DNA and RNA to form long chains of nucleotides through dehydration synthesis. This reaction results in a Phosphodiester Bond. - Each time a nucleotide is added, the free 5’ phosphate and the free 3’ hydroxyl group at the other end remain so thousands of bonds are possible. - We list nitrogen bases in a molecule of DNA from 5’ to 3’ and nucleotides can only be added to a template strand in a 5’ to 3’ direction.

17. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.8

18. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.9a,b

19. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.9c1

20. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.10b

21. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Three-Dimensional Structure of DNA X-ray diffraction suggested DNA had helical shape with a diameter of about 2 nanometers. Watson and Crick deduced DNA is a double helix with bases of two strands pointing inward forming base-pairs.  Purines pairing with pyrimidines. - Constant 2 nanometer diameter.  Strands are antiparallel with one running 5’ to 3’ (leading strand) and the other running 3’ to 5’ (lagging strand)

22. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

24. Semi-Conservative Replication Each chain in the helix is a complimentary mirror image of the other.  Double helix unzips and undergoes semi- conservative replication. - Each strand of the original duplex becomes one strand of another duplex. - One strand is conserved but the original DUPLEX is not.

25. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Replication Process Replication of DNA begins at one or more sites on the DNA molecule where there is a specific sequence of nucleotides called a replication origin.  DNA replicating enzyme DNA polymerase III and other enzymes add nucleotides to the growing complementary DNA strands.

26. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.13

27. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

28. Replication Process DNA polymerase cannot link the first nucleotides in a newly synthesized strand.  RNA polymerase (primase enzyme) constructs an RNA primer of about 10 nucleotides DNA polymerase adds nucleotides to 3’ end.  Leading strand replicates toward replication fork.  Lagging strand elongates from replication fork (so continually has to “backtrack” and add chunks of nucleotides – Okazaki Fragments)

29. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies DNA Replication Fork Copyright © McGraw-Hill Companies Permission required for reproduction or display

30. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.17

31. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Replication Process DNA ligase attaches fragments to lagging strand. Because synthesis of the leading strand is continuous, while the lagging strand is discontinuous, the overall replication of DNA is referred to as semidiscontinuous.

32. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Replication Process Opening DNA Double Helix  Initiating replication  Unwinding duplex (helicase enzyme)  Stabilizing single strands (single strand binding proteins) Building a Primer (RNA Primer called Primase) Assembling Complementary Strands (DNA Polymerase III) Removing the Primer (DNA Polymerase I) and add regular nucleotides Joining Okazaki Fragments (Ligase)

33. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Eukaryotic Replication In Eukaryotic cells, DNA is packaged in nucleosomes (wrapped around histone proteins) within chromosomes.  Each individual zone replicates as a discrete section called a replication unit or a replicon. - Each replication unit has its own origin of replication.  Fast Replication (approx 8 hours to replicate a chromosome in humans)

34. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies One-Gene/One-Polypeptide Hypothesis Genes produce their effects by specifying the structure of enzymes.  Each gene encodes the structure of one enzyme.  Enzymes are responsible for catalyzing the synthesis of nucleic acids, proteins, carbs, and lipids.  By encoding the structure of enzymes, DNA specifies the structure of the organism itself.

35. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Enzyme Deficiencies British physician Archibald Garrod concluded that patients suffering from certain diseases lacked the required enzymes to make them normal (Ex. Dystrophyn for muscular dystrophy). Stanford Geneticists Beadle and Tatum came up with the 1-Gene/1-Polypeptide Hypothesis based on their research that built on that of Garrod.

36. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 14.21

37. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Central Dogma All organisms use the same basic mechanism of reading and expressing genes. This is referred to as the CENTRAL DOGMA of biology. Information passes from the genes (DNA) -> an RNA copy of the gene (mRNA) -> sequential assembly of a chain of amino acids ( work of tRNA, rRNA, and ribosomes) General: DNA to RNA to PROTEINS

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39. Hardy-Weinberg Law HW Law: describes the conditions for genetic equilibrium and states that the proportions of dominant and recessive genes tend to remain constant in a randomly mating population unless there are outside influences. p(squared) + 2pq + q(squared) = 1; p+q=1 (homo dom) (hetero) (homo rec)

40. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Hardy-Weinberg Principle To maintain Hardy-Weinberg Equilibrium we must assume:  Population is very large.  Random mating  No mutation  No gene input from external sources.  No selection occurring

41. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Hardy-Weinberg Ratio frequency: proportion of individuals falling within a certain category in relation to the total number under consideration HW Ratio: ratio of genotype frequencies that evolve when mating is random and neither relocation or drift (random fluctuation in allele frequencies over time due to chance) are operating. Ex. Population of 100 cats Dd=48(black) DD=36(black) dd=16(white) (Dd X Dd) 48X48 = 2304 = 4 (constant) (DD X dd) 36X16 576 (ratio)

42. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Fig. 20.4

43. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Microevolution Microevolution: small changes in populations from generation to generation - Two primary causes of microevolution are genetic drift and natural selection Two main causes of genetic drift: - Bottleneck effect: most individuals of the pop. die off, leaving behind an overrepresentaion of alleles - Founder Effect: a few individuals leave the population to create a new population BOTH REDUCE THE POPULATION NUMBER SO THAT GENETIC DRIFT IS SIGNIFICANT

44. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Five Agents of Evolutionary Change 1. Mutation  Ultimate source of genetic variation and makes evolution possible 2. Gene Flow  Movement of alleles from one population to another.

45. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Five Agents of Evolutionary Change 3. Genetic Drift  Frequencies of particular alleles may change by chance alone. 4. Nonrandom Mating - Individuals with certain genotypes sometimes mate with one another more commonly than would be expected on a random basis and increases the expression of recessive alleleles (Inbreeding)

46. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Five Agents of Evolutionary Change 5. Selection  Artificial - Breeders exert selection.  Natural - Nature exerts selection..

47. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Forms of Selection Disruptive Selection  Selection eliminates intermediate types. Directional Selection  Selection eliminates one extreme from a phenotypic array. Stabilizing Selection  Selection acts to eliminate both extremes. - Fitness - Number of surviving offspring passed to the next generation.

48. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Types of Natural Selection