2. Chapter 12 Molecular Genetics
Section 1: DNA: The Genetic Material
Section 2: Replication of DNA
Section 3: DNA, RNA, and Protein
Section 4: Gene Regulation and Mutation

3. Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Griffith
Performed the first major experiment that led to the discovery of DNA as the genetic material

4. DNA is the genetic material
The First demonstration of bacterial transformation.
Experiments done by Frederick Griffith (in London) in 1928 found there were two different types of the bacterium Streptococcus pneumoniae:
An "S" or SMOOTH coat strain, which is lethal to mice.
An "R" or ROUGH strain, which will not hurt the mouse.
Griffith found that he could heat inactivate the smooth strain.

5. Fredrick Griffith
However, if he were to take a mixture of the heat-inactivated S strain, mixed with the R strain, the mouse would die. 
Thus there was some material in the heat-killed S strain that was responsible for "transforming" the R strain into a lethal form.
Fred Griffith (and a lab co-worker) was killed in their laboratory in 1940 from a German bomb. 

6. Griffith’s work continued in U.S.
in 1944, Oswald Avery, C.M. MacLeod, and M. McCarty carefully demonstrated that the ONLY material that was responsible for the transformation was DNA
Thus, DNA was the "Genetic material" - however, many scientists were still not sure that it was REALLY DNA (and not proteins) that was the genetic material.

7. Concluded that when the S cells were killed, DNA was released
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Oswald Avery
Identified the molecule that transformed the R strain of bacteria into the S strain
Concluded that when the S cells were killed, DNA was released
R bacteria incorporated this DNA into their cells and changed into S cells.

8. Used radioactive labeling to trace the DNA (P) and protein (S)
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Hershey and Chase (1952)
Used radioactive labeling to trace the DNA (P) and protein (S)
Concluded that the viral DNA was injected into the cell and provided the genetic information needed to produce new viruses

9. Chapter 12
Molecular Genetics

10. 12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
DNA Structure
Nucleotides
Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base

11. Chargaff’s rule: C = G and T = A
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Chargaff’s rule: C = G and T = A
Pyrimidines =
Cytosine and Thymine
Purines =
Guanine and Adenine
In 1950, Erwin Chargaff analyzed the base composition of DNA composition in a number of organisms.
He reported that DNA composition varies from one species to another. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein.

12. X-ray Diffraction Structure Analysis (1951-1952)
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
X-ray Diffraction Structure Analysis ( )
X-ray diffraction data helped solve the structure of DNA
Indicated that DNA was a double helix
This is the famous Rosalind
Franklin - Picture 51 which was leaked to James Watson and Francis
Crick by Maurice Wilkins.
Sodium deoxyribose nucleate from calf thymus, Structure B, Photo 51, taken by Rosalind E. Franklin and R.G. Gosling (her student). Linus Pauling's holographic annotations are to the right of the photo. May 2, 1952

13. X-ray Diffraction Rosalind Franklin (1920 - 1958)
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
X-ray Diffraction Rosalind Franklin ( )
The technique with which Maurice Wilkins and Franklin set out to do this is called X-ray crystallography.
With this technique a crystal is exposed to x-rays in order to produce a diffraction pattern.
If the crystal is pure enough and the diffraction pattern is acquired very carefully, it is possible to reconstruct the positions of the atoms in the molecules that comprise the basic unit of the crystal.
Rosalind Franklin died from cancer in April of 1958, at the age of 37.

14. two outside strands consist of alternating deoxyribose and phosphate
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Watson and Crick 1953
Built a model of the double helix that conformed to the others’ research
two outside strands consist of alternating
deoxyribose and phosphate
cytosine and guanine bases pair to each
other by three hydrogen bonds
thymine and adenine bases pair to each
other by two hydrogen bonds

15. Nobel Prize in Medicine/Physiology
The rules of the Nobel Prize forbid posthumous nominations; because Rosalind Franklin had died in 1958 she was not eligible for nomination to the Nobel Prize subsequently awarded to Crick, Watson, and Wilkins in 1962.
The award was for their body of work on nucleic acids and not exclusively for the discovery of the structure of DNA.
By the time of the award Wilkins had been working on the structure of DNA for over 10 years, and had done much to confirm the Crick-Watson model. Crick had been working on the genetic code at Cambridge and Watson had worked on RNA for some years.

16. DNA Structure – Double Helix
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
DNA Structure – Double Helix
DNA often is compared to a twisted ladder.
Rails of the ladder are represented by the alternating deoxyribose and phosphate.
The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

17. 12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Orientation
On the top rail, the strand is said to be oriented 5′ to 3′.
The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′.

18. 12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
12.1 DNA: The Genetic Material
Chromosome Structure
DNA coils around histones to form nucleosomes, which coil to form chromatin fibers.
The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis.

19. Semiconservative Replication
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Semiconservative Replication
Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and
one strand of new DNA.

20. Chapter 12
Molecular Genetics
12.2 Replication of DNA
Unwinding
DNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix.
RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand. Keeping the DNA strands separate.

21. Chapter 12
Molecular Genetics
12.2 Replication of DNA
Base pairing
DNA polymerase (an enzyme) continues adding appropriate nucleotides to the chain by adding to the 3′ end of the new DNA strand.

22. Chapter 12
Molecular Genetics

23. Chapter 12
Molecular Genetics
12.2 Replication of DNA
One strand is called the leading strand and is elongated as the DNA unwinds so is said to be synthesized continuously.
The other strand of DNA, called the lagging strand, elongates away from the replication fork.
The lagging strand is synthesized discontinuously into small segments, called Okazaki fragments.

24. DNA ligase links the two sections.
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Joining
DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides.
DNA ligase links the two sections.

25. Comparing DNA Replication in Eukaryotes and Prokaryotes
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Comparing DNA Replication in Eukaryotes and Prokaryotes
Eukaryotic DNA unwinds in multiple areas as DNA is replicated.
In prokaryotes, the circular DNA strand is opened at one origin of replication.

26. Central Dogma: DNA to RNA to Protein
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
Central Dogma: DNA to RNA to Protein
RNA
Contains the sugar ribose (instead of deoxyribose) and the base uracil (instead of thymine)
Usually is single stranded

27. Associates with proteins to form ribosomes in the cytoplasm
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
Messenger RNA (mRNA)
Long strands of RNA nucleotides that are formed complementary to one strand of DNA
Ribosomal RNA (rRNA)
Associates with proteins to form ribosomes in the cytoplasm
Transfer RNA (tRNA)
Smaller segments of RNA nucleotides that transport amino acids to the ribosome where proteins are made by adding 1 a.a. at a time

28. Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein

29. Chapter 12
Molecular Genetics

30. DNA is unzipped in the nucleus and RNA
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
Transcription
Through transcription, the DNA code is transferred to mRNA in the nucleus.
DNA is unzipped in the nucleus and RNA
polymerase binds to a specific section where an
mRNA will be synthesized.

31. Chapter 12
Molecular Genetics

32. Intervening sequences are called introns.
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
RNA Processing
The code on the DNA is interrupted periodically by sequences that are not in the final mRNA – introns removed..
Intervening sequences are called introns.
Remaining pieces of DNA that serve as the coding sequences are called exons.
DNA and Genes

33. The three-base code in DNA or mRNA is called a codon.
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
The Code
Experiments during the 1960s demonstrated that the DNA code was a three-base code.
The three-base code in DNA or mRNA is called a codon.

34. Each anticodon is complementary to a codon on the mRNA.
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
Translation
In translation, tRNA molecules act as the interpreters of the mRNA codon sequence.
At the middle of the folded strand, there is a three-base coding sequence called the anticodon.
Each anticodon is complementary to a codon on the mRNA.

35. 12.3 DNA, RNA, and Protein Chapter 12 Molecular Genetics
Visualizing Transcription
and Translation

36. Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
One Gene—One Enzyme
The Beadle and Tatum experiment showed that one gene codes for one enzyme. We now know that one gene codes for one polypeptide.
DNA from the Beginning

37. Prokaryote Gene Regulation
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Prokaryote Gene Regulation
Ability of an organism to control which genes are transcribed in response to the environment
An operon is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway.
Operator
Promoter
Regulatory gene
Genes coding for proteins

38. The Trp Operon 12.4 Gene Regulation and Mutation Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
The Trp Operon

39. The Lac Operon 12.4 Gene Regulation and Mutation Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
The Lac Operon
Lac-Trp Operon

40. Eukaryote Gene Regulation
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Eukaryote Gene Regulation
Controlling transcription
Transcription factors ensure that a gene is used at the right time and that proteins are made in the right amounts
The complex structure of eukaryotic DNA also regulates transcription.

41. Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Hox Genes
Hox genes are responsible for the general body pattern of most animals.

42. RNA interference can stop the mRNA from translating its message.
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
RNA Interference
RNA interference can stop the mRNA from translating its message.

43. A permanent change that occurs in a cell’s DNA is called a mutation.
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Mutations
A permanent change that occurs in a cell’s DNA is called a mutation.
Types of mutations
Point mutation
Insertion
Deletion

44. 12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation

45. Protein Folding and Stability
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Protein Folding and Stability
Substitutions also can lead to genetic disorders.
Can change both the folding and stability of the protein

46. Can occur spontaneously
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Causes of Mutation
Can occur spontaneously
Chemicals and radiation also can damage DNA.
High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.

47. Body-cell v. Sex-cell Mutation
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Body-cell v. Sex-cell Mutation
Somatic cell mutations are not passed on to the next generation.
Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.

48. Chapter Resource Menu Chapter Diagnostic Questions
Molecular Genetics
Chapter Resource Menu
Chapter Diagnostic Questions
Formative Test Questions
Chapter Assessment Questions
Standardized Test Practice
biologygmh.com
Glencoe Biology Transparencies
Image Bank
Vocabulary
Animation
Click on a hyperlink to view the corresponding lesson.

49. Which scientist(s) definitively proved
Chapter 12
Molecular Genetics
Chapter Diagnostic Questions
Which scientist(s) definitively proved
that DNA transfers genetic material?
Watson and Crick
Mendel
Hershey and Chase
Avery

50. Name the small segments of the lagging DNA strand.
Chapter 12
Molecular Genetics
Chapter Diagnostic Questions
Name the small segments of the lagging
DNA strand.
ligase
Okazaki fragments
polymerase
helicase

51. It contains the sugar deoxyribose. It contains the base uracil.
Chapter 12
Molecular Genetics
Chapter Diagnostic Questions
Which is not true of RNA?
It contains the sugar deoxyribose.
It contains the base uracil.
It is single-stranded.
It contains a phosphate.

52. The experiments of Avery, Hershey and
Chapter 12
Molecular Genetics
12.1 Formative Questions
The experiments of Avery, Hershey and
Chase provided evidence that the carrier
of genetic information is _______.
carbohydrate
DNA
lipid
protein

53. What is the base-pairing rule for purines
Chapter 12
Molecular Genetics
12.1 Formative Questions
What is the base-pairing rule for purines
and pyrimidines in the DNA molecule?
A—G and C—T
A—T and C—G
C—A and G—T
C—U and A—G

54. What are chromosomes composed of?
Chapter 12
Molecular Genetics
12.1 Formative Questions
What are chromosomes composed of?
chromatin and histones
DNA and protein
DNA and lipids
protein and centromeres

55. The work of Watson and Crick solved the mystery of how DNA works as a
Chapter 12
Molecular Genetics
12.2 Formative Questions
True or False
The work of Watson and Crick solved
the mystery of how DNA works as a
genetic code.

56. Which is not an enzyme involved in DNA replication?
Chapter 12
Molecular Genetics
12.2 Formative Questions
Which is not an enzyme involved in DNA
replication?
DNA ligase
DNA polymerase
Helicase
RNA primer

57. During DNA replication, what nucleotide
Chapter 12
Molecular Genetics
12.2 Formative Questions
During DNA replication, what nucleotide
base sequence is synthesized along an
original strand that has the sequence
TCAAGC?
AGTTCG
ATGGCG
CTGGAT
GACCTA

58. Which shows the basic chain of events
Chapter 12
Molecular Genetics
12.3 Formative Questions
Which shows the basic chain of events
in all organisms for reading and expressing
genes?
DNA RNA protein
RNA DNA protein
mRNA rRNA tRNA
RNA processing transcription
translation

59. In the RNA molecule, uracil replaces _______.
Chapter 12
Molecular Genetics
12.3 Formative Questions
In the RNA molecule, uracil replaces
_______.
adenine
cytosine
purine
thymine

60. Which diagram shows messenger RNA (mRNA)?
Chapter 12
Molecular Genetics
12.3 Formative Questions
Which diagram shows messenger
RNA (mRNA)? A. C. B. D.

61. What characteristic of the mRNA molecule
Chapter 12
Molecular Genetics
12.3 Formative Questions
What characteristic of the mRNA molecule
do scientists not yet understand?

62. intervening sequences in the mRNA molecule
Chapter 12
Molecular Genetics
12.3 Formative Questions
intervening sequences in the mRNA molecule
called introns
the original mRNA made in the nucleus called
the pre-mRNA
how the sequence of bases in the mRNA
molecule codes for amino acids
the function of many adenine nucleotides
at the 5′ end called the poly-A tail

63. Why do eukaryotic cells need a complex
Chapter 12
Molecular Genetics
12.4 Formative Questions
Why do eukaryotic cells need a complex
control system to regulate the expression
of genes?

64. All of an organism’s cells transcribe the same
Chapter 12
Molecular Genetics
12.4 Formative Questions
All of an organism’s cells transcribe the same
genes.
Expression of incorrect genes can lead to
mutations.
Certain genes are expressed more frequently
than others are.
Different genes are expressed at different
times in an organism’s lifetime.

65. Which type of gene causes cells to become specialized in structure in
Chapter 12
Molecular Genetics
12.4 Formative Questions
Which type of gene causes cells to
become specialized in structure in
function?
exon
Hox gene
intron
operon

66. What is an immediate result of a mutation in a gene?
Chapter 12
Molecular Genetics
12.4 Formative Questions
What is an immediate result of a mutation
in a gene?
cancer
genetic disorder
nonfunctional enzyme
amino acid deficiency

67. Which is the most highly mutagenic?
Chapter 12
Molecular Genetics
12.4 Formative Questions
Which is the most highly mutagenic?
chemicals in food
cigarette smoke
ultraviolet radiation
X rays

68. Look at the following figure. Identify the
Chapter 12
Molecular Genetics
Chapter Assessment Questions
Look at the following figure. Identify the
proteins that DNA first coils around.

69. chromatin fibers chromosomes histones nucleosome
Chapter 12
Molecular Genetics
Chapter Assessment Questions
chromatin fibers
chromosomes
histones
nucleosome

70. Explain how Hox genes affect an organism.
Chapter 12
Molecular Genetics
Chapter Assessment Questions
Explain how Hox genes affect an organism.
They determine size.
They determine body plan.
They determine sex.
They determine number
of body segments.

71. Explain the difference between body-cell and sex-cell mutation.
Chapter 12
Molecular Genetics
Chapter Assessment Questions
Explain the difference between body-cell
and sex-cell mutation.

72. Answer: A mutagen in a body cell becomes part of the genetic sequence
Chapter 12
Molecular Genetics
Chapter Assessment Questions
Answer: A mutagen in a body cell becomes
part of the genetic sequence
in that cell and in future daughter
cells. The cell may die or simply not
perform its normal function. These
mutations are not passed on to the
next generation. When mutations
occur in sex cells, they will be
present in every cell of the offspring.

73. What does this diagram show about the replication of DNA
Chapter 12
Molecular Genetics
Standardized Test Practice
What does this
diagram show about
the replication of DNA
in eukaryotic cells?

74. DNA is replicated only at certain places along
Chapter 12
Molecular Genetics
Standardized Test Practice
DNA is replicated only at certain places along
the chromosome.
DNA replication is both semicontinuous and
conservative.
Multiple areas of replication occur along the
chromosome at the same time.
The leading DNA strand is synthesized
discontinuously.

75. What is this process called?
Chapter 12
Molecular Genetics
Standardized Test Practice
What is this process called?

76. mRNA processing protein synthesis transcription translation
Chapter 12
Molecular Genetics
Standardized Test Practice
mRNA processing
protein synthesis
transcription
translation

77. TTCAGG TTCTGG What type of mutation results in this change
Chapter 12
Molecular Genetics
Standardized Test Practice
What type of mutation results in this change
in the DNA sequence?
TTCAGG TTCTGG
deletion
frameshift
insertion
substitution

78. How could RNA interference be used
Chapter 12
Molecular Genetics
Standardized Test Practice
How could RNA interference be used
to treat diseases such as cancer and
diabetes?

79. by activating genes to produce proteins that
Chapter 12
Molecular Genetics
Standardized Test Practice
by activating genes to produce proteins that
can overcome the disease
by interfering with DNA replication in cells
affected by the disease
by preventing the translation of mRNA into
the genes associated with the disease
by shutting down protein synthesis in the
cells of diseased tissues

80. The structure of a protein can be altered
Chapter 12
Molecular Genetics
Standardized Test Practice
True or False
The structure of a protein can be altered
dramatically by the exchange of a single
amino acid for another.

81. Glencoe Biology Transparencies
Chapter 12
Molecular Genetics
Glencoe Biology Transparencies

82. Chapter 12
Molecular Genetics
Image Bank

83. Chapter 12
Molecular Genetics
Image Bank

84. Section 1 Vocabulary double helix nucleosome Chapter 12
Molecular Genetics
Vocabulary
Section 1
double helix
nucleosome

85. Section 2 Vocabulary semiconservative replication DNA polymerase
Chapter 12
Molecular Genetics
Vocabulary
Section 2
semiconservative replication
DNA polymerase
Okazaki fragment

86. Section 3 Vocabulary RNA messenger RNA ribosomal RNA transfer RNA
Chapter 12
Molecular Genetics
Vocabulary
Section 3
RNA
messenger RNA
ribosomal RNA
transfer RNA
transcription
RNA polymerase
codon
intron
exon
translation

87. Section 4 Vocabulary gene regulation operon mutation mutagen
Chapter 12
Molecular Genetics
Vocabulary
Section 4
gene regulation
operon
mutation
mutagen

88. Visualizing Transcription and Translation
Chapter 12
Molecular Genetics
Animation
DNA Polymerase
Transcription
Visualizing Transcription and Translation
Lac-Trp Operon