Download DNA: The Genetic Material

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
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Click on a lesson name to select.
Section 1
Molecular Genetics
DNA: Discovery
Frederick Griffith - 1928
 Performed the first major experiment that led to
the discovery of DNA as the genetic material
 REFUTED THAT PROTEIN WAS THE GENETIC
MATERIAL – ANOTHER LARGE MOLECULE –DNA
CARRIED GENETIC INFO
Section 1
Molecular Genetics
DNA: The Genetic Material
Oswald Avery - 1944
 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.
 VERIFIED GRIFFITH’S EXPERIMENT
Section 1
Molecular Genetics
DNA: The Genetic Material
Hershey and Chase - 1952
 Used radioactive labeling to
trace the DNA and protein
 Concluded that the viral
DNA was injected into the
cell and provided the
genetic information needed
to produce new viruses
 CONFIRMED THAT DNA IS
THE GENETIC MATERIAL
Section 1
Molecular Genetics
DNA: The Genetic Material
DNA Structure
 Nucleotides
 Consist of a five-carbon sugar, a phosphate
group, and a nitrogenous base
Section 1
Molecular Genetics
Section 1
Molecular Genetics
DNA: The Genetic Material
Erwin Chargaff 1950
 Chargaff’s rule:
C = G and T = A
Section 1
Molecular Genetics
DNA: The Genetic Material
X-ray Diffraction
 Rosalind Franklin - 1951
 X-ray diffraction data helped solve the
structure of DNA
 Indicated that DNA was a double helix
Section 1
Molecular Genetics
DNA: The Genetic Material
Watson and Crick - 1953
 Built a model of the double helix that
conformed to the others’ research
1. two outside strands consist of alternating
deoxyribose and phosphate
2. cytosine and guanine bases pair to each
other by three hydrogen bonds
3. thymine and adenine bases pair to each
other by two hydrogen bonds
Cambridge University,
Cambridge
Kings College,
London
Section 1
Molecular Genetics
DNA: The Genetic Material
DNA Structure
 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.
Section 1
Molecular Genetics
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′.
Section 1
Molecular Genetics
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.
Section 2
Molecular Genetics
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.
• What is the complementary
strand for the DNA segment
ACTGGA?
Section 2
Molecular Genetics
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.
Section 2
Molecular Genetics
Replication of DNA
Base pairing
 DNA polymerase continues adding appropriate
nucleotides to the chain by adding to the 3′ end
of the new DNA strand.
Section 2
Molecular Genetics
Section 2
Molecular Genetics
Replication of DNA
 One strand is called the leading strand
and is elongated as the DNA unwinds.
 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.
Section 2
Molecular Genetics
Replication of DNA
Joining
 DNA polymerase removes the RNA primer
and fills in the place with DNA nucleotides.
 DNA ligase links the two sections.
Section 2
Molecular Genetics
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.
Section 3
Molecular Genetics
Section 3
Molecular Genetics
DNA, RNA, and Protein
 RNA
 Contains the sugar ribose and the
base uracil instead of thymine
 Usually is single stranded
Section 3
Molecular Genetics
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
Section 3
Molecular Genetics
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.
Transcribe A C A G G A
Section 3
Molecular Genetics
DNA, RNA, and Protein
RNA Processing
 The code on the DNA is interrupted
periodically by sequences that are not in the
final mRNA.
 Intervening sequences are called introns.
 Remaining pieces of DNA that serve as the
coding sequences are called exons.
DNA and Genes
Section 3
Molecular Genetics
DNA, RNA, and Protein
The mRNA 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.
Section 3
Molecular Genetics
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.
• According to the mRNA Genetic Code which
amino acid sequence would most likely be
determined by a section of DNA molecule
with the base sequence:
• A-C-A-G-G-A-T-C-A
Section 3
Molecular Genetics
DNA, RNA, and Protein
One Gene—
One Enzyme
 The Beadle and Tatum
(1941) experiment
showed that one gene
codes for one enzyme.
We now know that one
gene codes for one
polypeptide.
Section 4
Molecular Genetics
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.
Section 4
Molecular Genetics
Gene Regulation and Mutation
Hox Genes
 Hox genes are
responsible for
the general body
pattern of most
animals.
Section 4
Molecular Genetics
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
Section 4
Molecular Genetics
THE BIG RAT CAT ATE THE WET BAT
Section 4
Molecular Genetics
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
Section 4
Molecular Genetics
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.
Section 4
Molecular Genetics
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.
Chapter
Molecular Genetics
Chapter Diagnostic
Questions
Which scientist(s) definitively proved
that DNA transfers genetic material?
A. Watson and Crick
B. Mendel
C. Hershey and Chase
D. Avery
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Chapter Diagnostic
Questions
During which stage of the cell cycle
does DNA replication take place?
A. Growth
B. Prophase
C. Synthesis
D. Mitosis
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Chapter Diagnostic
Questions
Name the small segments of the lagging
DNA strand.
A. ligase
B. Okazaki fragments
C. micro RNA
D. helicase
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Chapter Diagnostic
Questions
Which is not true of RNA?
A. It contains the sugar ribose.
B. It contains the base uracil.
C. It is single-stranded.
D. It contains a phosphate.
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 1 Formative
Questions
The experiments of Avery, Hershey and
Chase provided evidence that the carrier
of genetic information is _______.
A. carbohydrate
B. DNA
C. lipid
D. protein
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 1 Formative
Questions
What is the base-pairing rule for purines
and pyrimidines in the DNA molecule?
A. A—G and C—T
B. A—T and C—G
C. C—A and G—T
D. C—U and A—G
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 1 Formative
Questions
What are chromosomes composed of?
A.chromatin and histones
B. DNA and protein
C. DNA and lipids
D. protein and centromeres
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 2 Formative
Questions
The work of Watson and
Crick solved the mystery
of how DNA works as a
genetic code.
A. True
B. False
1.
2.
A
B
Chapter
Molecular Genetics
Section 2 Formative
Questions
Which is not an enzyme involved in DNA
replication?
A. DNA ligase
B. DNA polymerase
C. helicase
D. RNA primer
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 3 Formative
Questions
Which shows the basic chain of events
in all organisms for reading and expressing
genes?
A. DNA  RNA  protein
B. RNA  DNA  protein
1.
A
C. mRNA  rRNA  tRNA
2.
B
3.
C
D. RNA processing  transcription 4. translation
D
Chapter
Molecular Genetics
Section 3 Formative
Questions
In the RNA molecule, uracil replaces
_______.
A. adenine
B. cytosine
C. purine
D. thymine
1.
2.
3.
4.
A
B
C
D
Molecular Genetics
Chapter
Section 3 Formative
Questions
Which diagram shows messenger
RNA (mRNA)?
A.
C.
B.
D.
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 3 Formative
Questions
What characteristic of the mRNA molecule do scientists
not yet understand?
A. intervening sequences in the mRNA molecule called
introns
B. the original mRNA made in the nucleus called the
pre-mRNA
C. how the sequence of bases in the mRNA
1. molecule
A
2.
B
codes for amino acids
3.
C
4.
D
D. the function of many adenine nucleotides
at the
5′
end called the poly-A tail
Chapter
Molecular Genetics
Section 4 Formative
Questions
Why do eukaryotic cells need a complex control system
to regulate the expression of genes?
A. All of an organism’s cells transcribe the same genes.
B. Expression of incorrect genes can lead to mutations.
C. Certain genes are expressed more frequently than
others are.
1.
2.
3.
4.
A
B
C
D
D. Different genes are expressed at different times in an
organism’s lifetime.
Chapter
Molecular Genetics
Section 4 Formative
Questions
Which type of gene causes cells to
become specialized in structure in
function?
A. exon
B. Hox gene
C. intron
D. operon
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 4 Formative
Questions
What is a result of a mutation
in a gene?
A. cancer
B. genetic disorder
C. nonfunctional enzyme
D. amino acid deficiency
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Section 4 Formative
Questions
Which is the most highly mutagenic?
A. chemicals in food
B. cigarette smoke
C. ultraviolet radiation
D. X rays
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Chapter Assessment
Questions
Look at the following
figure. Identify the
proteins that DNA
first coils around.
A. chromatin fibers
B. chromosomes
C. histones
D. nucleosome
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Chapter Assessment
Questions
Explain how Hox genes affect
an organism.
A. They determine size.
B. They determine body plan.
C. They determine sex.
1.
A
2.
B
D. They determine number of body segments.
3.
C
4.
D
Chapter
Molecular Genetics
Chapter Assessment
Questions
Explain the difference between body-cell and
sex-cell mutation.
Answer: A mutagen in a body cell becomes
part of the 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.
Chapter
Molecular Genetics
Standardized Test
Practice
What does this diagram show about the
replication of DNA in eukaryotic cells?
A. DNA is replicated only at certain
places along the chromosome.
B. DNA replication is both
semicontinuous and conservative.
C. Multiple areas of replication occur
along the chromosome at the
same time.
D. The leading DNA strand is
synthesized discontinuously.
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Standardized Test
Practice
What is this
process called?
A. mRNA processing
B. protein synthesis
C. transcription
D. translation
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Standardized Test
Practice
What type of mutation results in this change
in the DNA sequence?
TTCAGG
A. deletion
B. frameshift
C. insertion
D. substitution
TTCTGG
1.
2.
3.
4.
A
B
C
D
Chapter
Molecular Genetics
Standardized Test
Practice
The structure of a protein can be altered
dramatically by the exchange of a single
amino acid for another.
A. True
B. False
1.
2.
A
B