1. THE STRUCTURE OF DNA
Section 10-1

2. WHICH IS MORE LIKELY TO BE GENETIC
MATERIAL?
Protein DNA

3. THE TALE OF DNA
 1904: Thomas Hunt Morgan – white-eyed fly
showed that chromosomes were the heart of
inheritance

4. FREDERICK GRIFFITH’S EXPERIMENTS
 Two types of bacteria:
 S-strain covered by a capsule and
causes pneumonia
 R-strain had no capsule and was
not dangerous
 Heat-killed S bacteria (capsule still
present) were harmless

5. FREDERICK GRIFFITH’S RESULTS

6. FREDERICK GRIFFITH’S RESULTS
 R bacteria (safe) mixed with
heat-killed S bacteria (capsule
still present) killed the mouse
 Griffith’s discovery:
TRANSFORMATION, the
uptake of foreign genetic
material

7. OSWALD AVERY’S EXPERIMENT
 Repeated Griffith’s experiments,
utilizing enzymes to destroy
DNA, RNA, and protein,
respectively
 Missing protein?
Transformation still occurs
 Missing DNA? No
transformation

8. HERSHEY-CHASE EXPERIMENT
 How do proteins and
DNA cross cell
membranes?
 STEP 1: Viral proteins
and DNA “marked”
with two different
radioactive elements

9. HERSHEY-CHASE EXPERIMENT
 STEP 2: Viruses
“infect” bacteria
 STEP 3: Radioactive
elements can be
detected by machines
 STEP 4: Examine
infected bacteria to find
radioactive proteins or
DNA

10. UNRAVELING DNA
 Linus Pauling (Caltech) pioneered X-ray
crystallography
 James Watson and Francis Crick working on
structure at Cambridge (England) using cardboard
cutouts “like a puzzle”
 Rosalind Franklin’s X-ray images taken by Maurice
Wilkins and shown to Watson

11. DNA
 DNA = DeoxyriboNucleic Acid
 Sugar (“-ose”) in DNA is called
deoxyribose
 Each NUCLEOTIDE (piece of DNA)
consists of (1) a sugar, (2) a
phosphate, and (3) a nitrogenous
base

12. NITROGENOUS BASES
 4 different bases; 2 types
 Purines (Adenine and
Guanine) are 2-ringed
 Pyrimidines (Thymine and
Cytosine) are 1-ringed

13. ERWIN CHARGAFF’S OBSERVATIONS
 Amount of adenine always equals amount of thymine
 (And C = G, too!)

15. WATSON AND CRICK: “THE DOUBLE HELIX”

16. DNA’S SHAPE
 “Spiral staircase” or
double helix
 1953 publication
 1962 Nobel Prize for
Watson, Crick, and
Wilkins

17. BASE PAIRS
 Adenine – Thymine
 Cytosine – Guanine
 Two strands held
together by weak
hydrogen bonds

18. BASE PAIRS
 Adenine – Thymine
 Cytosine – Guanine
 Two strands held
together by weak
hydrogen bonds

19. WHAT IS THE COMPLEMENTARY STRAND?
 A C G C C A G T A
 T G C G G T C A T

20. REPLICATION OF DNA
Section 10-2

21. REASON FOR REPLICATION
 Each new cell contains a
complete, exact copy of DNA
 REPLICATION: Process by
which DNA is copied

22. STEPS IN REPLICATION
 Helix unwinds, creating
Y-shaped “replication
forks”
 New strand created
when complementary
nucleotides are paired
with each original
strand
 Eventually, two new
identical helixes form

23. PROTEINS AND ENZYMES
 Proteins: most
important structural
and functional
molecules in the cell
 Enzymes: proteins
that act as catalysts
(cause reactions)
 Enzymes end in -ase

24. DNA HELICASE
 Wedges between two strands of double helix
 Breaks weak hydrogen bonds
 Unwinds DNA before replication

25. DNA POLYMERASE
 Moves along
strand, adding
complementary
nucleotides
 Not able to
continue if wrong
base is paired
(“proofreading”)

26. THE WORK OF DNA POLYMERASE
 What DNA strand would
be created to match this
strand?
 G A C G A T C G A

27. TRANSCRIPTION AND TRANSLATION
Section 10-3

28. WIKIPEDIA
 Transcription may refer to:
 Transcription (linguistics), the conversion of spoken
words into written language. Also the conversion of
handwriting, or a photograph of text into pure text
 Transcription (music), either notating an unnotated
piece, common in ethnomusicology, or rewriting a
piece, either simply recopying (as for clarity), or as
an arrangement for another instrument

29. FUNCTION OF DNA
 DNA codes for proteins
, which perform most
cell functions
 Where are proteins
made?
 Where is DNA?
 See a problem?

30. DNA CODES FOR PROTEINS
 A molecule called RNA
carries the message
from DNA to the
ribosome, where the
protein is created
 Very similar to DNA –
few exceptions

31. RNA VS. DNA
 Double-stranded
 Deoxyribose sugar
 Thymine (T) base
 Single-stranded
 Ribose sugar
 Uracil (U) base
DNA RNA

32. DNA  PROTEIN
 RNA created from the
message in a strand of
DNA
 Occurs in nucleus
 Protein created from
message in a strand of
RNA
 “Language” of N.A.s
changed to “language”
of amino acids
 Occurs at ribosome
Transcription Translation

33. TRANSCRIPTION

34. TRANSCRIPTION
 RNA polymerase bonds to
DNA at a specific site called the
promoter and unwinds DNA
 Complimentary RNA bases
added as RNA polymerase
moves along the DNA
 Result is a strand of mRNA,
one of three types

35. RESULTS OF TRANSCRIPTION
 What strand of mRNA would be made from the
following strand of DNA?
DNA: T C C G A C C A G T C A

36. RESULTS OF TRANSCRIPTION
 What strand of mRNA would be made from the
following strand of DNA?
DNA: T C C G A C C A G T C A
RNA: A G G C U G G U C A G U

37. TRANSLATION

38. JOB OF MRNA
 mRNA (messenger RNA)
takes DNA “message” from
nucleus to ribosome
 Ribosomes read mRNA and
create appropriate chain of
amino acids (polypeptide or
protein)

39. CODONS
 Three-base sections of mRNA
 “Code” for one of 20 amino
acids
 How many different
combinations can be made?

40. HOW TRANSLATION OCCURS
 Changes message
from “language” of
nucleic acids into
“language” of proteins
 Three types of RNA
interact

41. TWO MORE TYPES OF RNA
 rRNA – makes up
a large portion of
the ribosome
structure
 tRNA – compact
molecule which
“grabs” amino
acids and matches
them to mRNA

42. STEPS OF TRANSLATION
1. Each tRNA molecule has an
anticodon, complementary
to a codon, and carries a
specific amino acid
2. Specific tRNA molecule
binds to correct codon of
mRNA

43. STEPS OF TRANSLATION
3. Ribosome moves down
the mRNA strand
4. Second tRNA binds to
next codon
5. Peptide bond forms
between two amino acids
6. First tRNA leaves the
molecule

44. STEPS OF TRANSLATION
7. Continues until a “Stop Codon” is reached
8. Chain of amino acids (called a polypeptide or protein)
falls away from mRNA molecule and ribosome

45. EXAMPLE FROM TEXTBOOK
 Keratin is on of the proteins in hair. The gene for
keratin is transcribed and translated by certain skin
cells. The sequence below is part of the mRNA
molecule that is transcribed from the gene for keratin.
U C U C G U G A A U U U U C C

46. ANSWER THESE QUESTIONS.
U C U C G U G A A U U U U C C
1. Determine the sequence of DNA that was
transcribed to create the mRNA strand shown
above.
2. Determine the sequence of amino acids that will
result from the translation of the segment of
mRNA above.

47. 2nd Base
1stBase

49. GENE EXPRESSION
 Complex relationships
between genes and their
outcomes
 Most traits are not controlled
by one gene or one protein
 Mistakes and variations
occur regularly
 Not all cells express all
genes

50. REVIEW
 Answer the questions regarding the strand of DNA
below.
T A C G C G A G T A C C A C T
1. What is the complementary strand of DNA?
2. What RNA strand would be created through
transcription? (Use original DNA strand.)
3. What polypeptide (chain of amino acids) would be
created through translation?

51. MUTATIONS
Section 14-1

52. MUTATIONS
 Changes in
structure/amount of DNA
 Cause genetic variation (or
worse)
 Essential to evolution
 Darwin is my favorite
scientist

53. CAUSES
 Some mistakes in replication are not repaired
 Increased rate due to radiation and some chemicals

54. EFFECTS
 Changes in amino acids
(proteins) result in specific
diseases or in non-
functional cell parts
 Some mutations can be
beneficial over time.

55. TYPES
 Point Mutation: change
in single base
 Insertion
 Deletion
 Substitution

56. HOW DO MUTATIONS AFFECT PROTEINS?
A T G C C A T A G
 What amino acids result from this DNA?
1. Change second A to T. (Silent mutation.)
2. Change second C to A. (Missense mutation.)
3. Add G before first C. (Frameshift mutation.)

57. OTHER TYPES
 Nonsense mutation –
amino acid code
changed to a “stop”
signal.

58. EFFECTS OF GENETIC CHANGE
 Changes in egg/sperm cells are
heritable (genetic disorders)
 Mutations in genes that control
cell growth and division cause
tumors
 New alleles (new traits) can be
created – beneficial or harmful?

59. GENETIC DISORDERS
 Sickle cell anemia
 Tay-Sachs disease
 Cystic Fibrosis
 Hemophilia A
 Huntington’s disease
 Downs Syndrome***

60. REGULATING GENE EXPRESSION
Section 14-2

61. GENE EXPRESSION
 Which genes are “used” by
a cell?
 Controlled by complex
regulatory systems which
take into account
environmental and other
factors
 Some expression can be
turned on/off to use
materials more efficiently

62. OPERONS
 Gene-regulation
system in which DNA
controls the expression
of related genes
 Common in
prokaryotes
 Often controlled by
environmental factors

63. LAC OPERON
 E. Coli cells live in your stomach and digest lactose
 Need 3 different enzymes (3 different genes) to do
this
 Controlled by system called “lac operon”

64. IN EUKARYOTES
 Transcription factors
affect the binding of
RNA polymerase to
the promoter
 Examples: Activators
and repressors bond
to operators

65. REGULATION AFTER TRANSCRIPTION
 Some sequences of
RNA do not code for
proteins
 Coding sequences:
exons
 Non-coding
sequences: introns

66. REGULATION AFTER TRANSCRIPTION
 Certain proteins remove introns and splice (re-join)
exons together
 Exons leave nucleus to be translated in ribosome