1. Chapter 9 Topics - Genetics - Flow of Genetics - Regulation - Mutation
- Recombination

2. Genetics
Genome
Chromosome
Gene
Protein
Genotype
Phenotype

3. The sum total of genetic material of a cell is referred to as the genome.
Fig. 9.2 The general location and forms of the genome

4. Chromosome Procaryotic Eucaryotic
Histonelike proteins condense DNA
Eucaryotic
Histone proteins condense DNA
Subdivided into basic informational packets called genes

5. Genes Three categories Genotype Phenotype Structural Regulatory
Encode for RNA
Genotype
sum of all gene types
Phenotype
Expression of the genotypes

6. Flow of Genetics DNA =>RNA=>Protein Replication Transcription
Translation

7. Representation of the flow of genetic information.
Fig. 9.9 Summary of the flow of genetic information in cell.

8. DNA
Structure
Replication

9. DNA is lengthy and occupies a small part of the cell by coiling up into a smaller package.
Fig. 9.3 An Escherichia coli cell disrupted to release its
DNA molecule.

10. Structure Nucleotide Double stranded helix Phosphate Deoxyribose sugar
Nitrogenous base
Double stranded helix
Antiparallel arrangement

11. Nitrogenous bases
Purines
Adenine
Guanine
Pyrimidines
Thymine
Cytosine

12. Purines and pyrimidines pair (A-T or G-C) and the sugars (backbone) are linked by a phosphate.
Fig. 9.4 Three views of DNA structure

13. Replication Semiconservative Enzymes Leading strand Lagging strand
Okazaki fragments

14. Semiconservative
New strands are synthesized in 5’ to 3’ direction

15. Semiconservative replication of DNA synthesizes a new strand of DNA from a template strand.
Fig. 9.5 Simplified steps to show the semiconservative
replication of DNA

16. Enzymes Helicase DNA polymerase III Primase DNA polymerase I Ligase
Gyrase

17. The function of important enzymes involved in DNA replication.
Table 9.1 Some enzymes involved in DNA replication

18. Leading strand
RNA primer initiates the 5’ to 3’ synthesis of DNA in continuous manner

19. Lagging strand Multiple Okazaki fragments are synthesized
Okazaki fragments are ligated together to form one continuous strand

20. The steps associated with the DNA replication process.
Fig. 9.6 The bacterial replicon: a model for DNA
Synthesis

21. Replication processes from other biological systems (plasmids, viruses) involve a rolling cycle.
Fig. 9.8 Simplified model of rolling circle DNA
Replication

22. RNA Transcription Codon Message RNA (mRNA) Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Codon

23. Transcription
A single strand of RNA is transcribed from a template strand of DNA
RNA polymerase catalyzes the reaction
Synthesis in 5’ to 3’ direction

24. mRNA Copy of a structural gene or genes of DNA
Can encode for multiple proteins on one message
Thymidine is replaced by uracil
The message contains a codon (three bases)

25. The synthesis of mRNA from DNA.
Fig The major events in mRNA synthesis

26. tRNA Copy of specific regions of DNA
Complimentary sequences form hairpin loops
Amino acid attachment site
Anticodon
Participates in translation (protein synthesis)

27. Important structural characteristics for tRNA and mRNA.
Fig Characteristics of transfer and message RNA

28. rRNA Consist of two subunits (70S)
A subunit is composed of rRNA and protein
Participates in translation

29. Ribosomes bind to the mRNA, enabling tRNAs to bind, followed by protein synthesis.
Fig. 9.9 Summary of the flow of genetics

30. Codons Triplet code that specifies a given amino acid
Multiple codes for one amino acid
20 amino acids
Start codon
Stop codons

31. The codons from mRNA specify a given amino acid.
Fig The Genetic code

32. Representation of the codons and their corresponding amino acids.
Fig Interpreting the DNA code

33. Protein Translation Protein synthesis have the following participants
mRNA
tRNA with attached amino acid
Ribosome

34. Participants involved in the translation process.
Fig The “players” in translation

35. Translation Ribosomes bind mRNA near the start codon (ex. AUG)
tRNA anticodon with attached amino acid binds to the start codon
Ribosomes move to the next codon, allowing a new tRNA to bind and add another amino acid
Series of amino acids form peptide bonds
Stop codon terminates translation

36. The process of translation.
Fig The events in protein synthesis

37. For procaryotes, translation can occur at multiple sites on the mRNA while the message is still being transcribed.
Fig Speeding up the protein assembly line in bacteria

38. Transcription and translation in eucaryotes
Similar to procaryotes except
AUG encodes for a different form of methionine
mRNA code for one protein
Transcription and translation are not simultaneous
Pre-mRNA
Introns
Exons

39. The processing of pre-mRNA into mRNA involves the removal of introns.
Fig The split gene of eucaryotes

40. Regulation Lactose operon Repressible operon Antimicrobials sugar
Amino acids, nucleotides
Antimicrobials

41. The regulation of sugar metabolism such as lactose involves repression in the absence of lactose, and induction when lactose is present.
Fig The lactose operon in bacteria

42. The regulation of amino acids such as arginine involves repression when arginine accumulates, and no repression when arginine is being used.
Fig Repressible operon

43. Antimicrobials
Ex. Antibiotics and drugs can inhibit the enzymes involved in transcription and translation

44. Mutations Changes made to the DNA Spontaneous – random change
Induced – chemical, radiation.
Point – change a single base
Nonsense – change a normal codon into a stop codon
Back-mutation – mutation is reversed
Frameshift – reading frame of the mRNA changes

45. Examples of chemical and radioactive mutagens, and their effects.
Table 9.3 Selected mutagenic agents and their effects

46. Repair of mutations involves enzymes recognizing, removing, and replacing the bases.
Fig Excision repair of mutation by enzymes

47. The Ames test is used to screen environmental and dietary chemicals for mutagenicity and carcinogenicity without using animal studies.
Fig The Ames test.

48. Effects of mutations Positive effects for the cell
Allow cells to adapt
Negative effects for the cell
Loss of function
Cells cannot survive

49. Recombination Sharing or recombining parts of their genome Conjugation
Transformation
Transduction

50. Conjugation
Transfer of plasmid DNA from a F+ (F factor) cell to a F- cell
An F+ bacterium possesses a pilus
Pilus attaches to the recipient cell and creates pore for the transfer DNA
High frequency recombination (Hfr) donors contain the F factor in the chromosome

51. Conjugation is the genetic transmission through direct contact between cells.
Fig Conjugation: genetic transmission through direct contact

52. Transformation
Nonspecific acceptance of free DNA by the cell (ex. DNA fragments, plasmids)
DNA can be inserted into the chromosome
Competent cells readily accept DNA

53. DNA released from a killed cell can be accepted by a live competent cell, expressing a new phenotype.
Fig Griffith’s classic experiment in transformation

54. Transduction Bacteriophage infect host cells
Serve as the carrier of DNA from a donor cell to a recipient cell
Generalized
Specialized

55. Genetic transfer based on generalized transduction.
Fig Generalized transduction

56. Genetic transfer based on specialized transduction.
Fig Specialized transduction

57. Transposon “Jumping genes” Exist in plasmids and chromosomes
Contains genes that encode for enzymes that remove and reintegrate the transposon
Small transposons are called insertion elements

58. Movement of transposons can occur in plasmids and chromosomes.
Fig Transposons: shifting segments of the genome