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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
http://student.ccbcmd.edu/~gkaiser/biotutorials/index.html
http://glencoe.mcgraw-hill.com/sites/0078757134/student_view0/
http://library.thinkquest.org/C0118084/Genetic_Engineering.htm
12.1 DNA: The Genetic Material
Molecular GeneticsChapter 12
Griffith Performed the first major experiment that led to
the discovery of DNA as the genetic material
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.
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.
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.
Molecular Genetics
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.
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
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
12.1 DNA: The Genetic Material
Chapter 12
Molecular GeneticsChapter 12
Molecular Genetics
DNA Structure Nucleotides
Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
Chargaff’s rule: C = G and T = A
Pyrimidines = Cytosine and Thymine
Purines = Guanine and Adenine
12.1 DNA: The Genetic Material
Chapter 12
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.
Molecular Genetics
X-ray Diffraction Structure Analysis (1951-1952) X-ray diffraction data helped
solve the structure of DNA Indicated that DNA was a double helix
12.1 DNA: The Genetic Material
Chapter 12
This is the famous RosalindFranklin - 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
Molecular Genetics
X-ray Diffraction Rosalind Franklin (1920 - 1958) 12.1 DNA: The Genetic Material
Chapter 12
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.
Molecular Genetics
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
12.1 DNA: The Genetic Material
Chapter 12
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.
Molecular Genetics
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.
12.1 DNA: The Genetic Material
Chapter 12
Molecular Genetics
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′.
12.1 DNA: The Genetic Material
Chapter 12
12.1 DNA: The Genetic Material
Molecular Genetics
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.
Chapter 12
12.2 Replication of DNA
Molecular Genetics
Semiconservative Replication
Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA andone strand of new DNA.
Chapter 12
Molecular Genetics
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.
12.2 Replication of DNA
Chapter 12
Molecular Genetics
Base pairing
DNA polymerase (an enzyme) continues adding appropriate nucleotides to the chain by adding to the 3′ end of the new DNA strand.
12.2 Replication of DNA
Chapter 12
Molecular GeneticsChapter 12
Molecular Genetics
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.
12.2 Replication of DNA
Chapter 12
Molecular Genetics
Joining
DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides.
DNA ligase links the two sections.
12.2 Replication of DNA
Chapter 12
12.2 Replication of DNA
Molecular Genetics
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.
Chapter 12
12.3 DNA, RNA, and Protein
Molecular Genetics
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
Chapter 12
Molecular Genetics
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
12.3 DNA, RNA, and Protein
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
Chapter 12
Molecular GeneticsChapter 12
DNA is unzipped in the nucleus and RNA polymerase binds to a specific section where an mRNA will be synthesized.
Molecular Genetics
Transcription
Through transcription, the DNA code is transferred to mRNA in the nucleus.
12.3 DNA, RNA, and Protein
Chapter 12
Molecular GeneticsChapter 12
Molecular Genetics
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.
12.3 DNA, RNA, and Protein
Chapter 12
DNA and Genes
Molecular Genetics
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.
12.3 DNA, RNA, and Protein
Chapter 12
Molecular Genetics
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.
12.3 DNA, RNA, and Protein
Chapter 12
Molecular Genetics
12.3 DNA, RNA, and Protein
Chapter 12
Visualizing Transcription and Translation
12.3 DNA, RNA, and Protein
Molecular Genetics
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.
Chapter 12
DNA from the Beginning
12.4 Gene Regulation and Mutation
Molecular Genetics
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
Chapter 12
Molecular Genetics
The Trp Operon
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
The Lac Operon
12.4 Gene Regulation and Mutation
Chapter 12
Lac-Trp Operon
Molecular Genetics
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.
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
Hox Genes
Hox genes are responsible for the general body pattern of most animals.
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
RNA Interference
RNA interference can stop the mRNA from translating its message.
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
Mutations
A permanent change that occurs in a cell’s DNA is called a mutation.
Types of mutations
Point mutation Insertion Deletion
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
Protein Folding and Stability
Substitutions also can lead to genetic disorders.
Can change both the folding and stability of the protein
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
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.
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
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.
12.4 Gene Regulation and Mutation
Chapter 12
Molecular Genetics
Chapter Resource Menu
Chapter Diagnostic Questions
Formative Test Questions
Chapter Assessment Questions
Standardized Test Practice
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Chapter 12
A. Watson and Crick
B. Mendel
C. Hershey and Chase
D. Avery
Which scientist(s) definitively proved that DNA transfers genetic material?
Molecular Genetics
Chapter Diagnostic Questions
Chapter 12
A. ligase
B. Okazaki fragments
C. polymerase
D. helicase
Name the small segments of the lagging DNA strand.
Molecular Genetics
Chapter Diagnostic Questions
Chapter 12
A. It contains the sugar deoxyribose.
B. It contains the base uracil.
C. It is single-stranded.
D. It contains a phosphate.
Which is not true of RNA?
Molecular Genetics
Chapter Diagnostic Questions
Chapter 12
A. carbohydrate
B. DNA
C. lipid
D. protein
The experiments of Avery, Hershey and Chase provided evidence that the carrier of genetic information is _______.
Molecular Genetics
12.1 Formative Questions
Chapter 12
A. A—G and C—T
B. A—T and C—G
C. C—A and G—T
D. C—U and A—G
What is the base-pairing rule for purines and pyrimidines in the DNA molecule?
Molecular Genetics
12.1 Formative Questions
Chapter 12
A.chromatin and histones
B. DNA and protein
C. DNA and lipids
D. protein and centromeres
What are chromosomes composed of?
Molecular Genetics
12.1 Formative Questions
Chapter 12
True or False
The work of Watson and Crick solved the mystery of how DNA works as a genetic code.
Molecular Genetics
12.2 Formative Questions
Chapter 12
A. DNA ligase
B. DNA polymerase
C. Helicase
D. RNA primer
Which is not an enzyme involved in DNA replication?
Molecular Genetics
12.2 Formative Questions
Chapter 12
A. AGTTCG
B. ATGGCG
C. CTGGAT
D. GACCTA
During DNA replication, what nucleotide base sequence is synthesized along an original strand that has the sequence TCAAGC?
Molecular Genetics
12.2 Formative Questions
Chapter 12
Which shows the basic chain of events in all organisms for reading and expressing genes?
A. DNA RNA protein
B. RNA DNA protein
C. mRNA rRNA tRNA
Molecular Genetics
D. RNA processing transcriptiontranslation
12.3 Formative Questions
Chapter 12
In the RNA molecule, uracil replaces _______.
A. adenine
B. cytosine
C. purine
D. thymine
Molecular Genetics
12.3 Formative Questions
Chapter 12
Which diagram shows messenger RNA (mRNA)?
Molecular Genetics
12.3 Formative Questions
Chapter 12
A.
B.
C.
D.
What characteristic of the mRNA molecule do scientists not yet understand?
Molecular Genetics
12.3 Formative Questions
Chapter 12
A. intervening sequences in the mRNA molecule
called intronsB. the original mRNA made in the nucleus called
the pre-mRNAC. how the sequence of bases in the mRNA
molecule codes for amino acidsD. the function of many adenine nucleotides
at the 5′ end called the poly-A tail
Molecular Genetics
12.3 Formative Questions
Chapter 12
Why do eukaryotic cells need a complex control system to regulate the expression of genes?
Molecular Genetics
12.4 Formative Questions
Chapter 12
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 frequentlythan others are.
D. Different genes are expressed at differenttimes in an organism’s lifetime.
Molecular Genetics
12.4 Formative Questions
Chapter 12
Which type of gene causes cells to become specialized in structure in function?
A. exon
B. Hox gene
C. intron
D. operon
Molecular Genetics
12.4 Formative Questions
Chapter 12
What is an immediate result of a mutation in a gene?
A. cancer
B. genetic disorder
C. nonfunctional enzyme
D. amino acid deficiency
Molecular Genetics
12.4 Formative Questions
Chapter 12
Which is the most highly mutagenic?
A. chemicals in food
B. cigarette smoke
C. ultraviolet radiation
D. X rays
Molecular Genetics
12.4 Formative Questions
Chapter 12
Look at the following figure. Identify the proteins that DNA first coils around.
Molecular Genetics
Chapter Assessment Questions
Chapter 12
A. chromatin fibers
B. chromosomes
C. histones
D. nucleosome
Molecular Genetics
Chapter Assessment Questions
Chapter 12
A. They determine size.
B. They determine body plan.
C. They determine sex.
Explain how Hox genes affect an organism.
Molecular Genetics
Chapter Assessment Questions
Chapter 12
D. They determine numberof body segments.
Explain the difference between body-cell and sex-cell mutation.
Molecular Genetics
Chapter Assessment Questions
Chapter 12
Molecular Genetics
Answer: A mutagen in a body cell becomespart 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 Assessment Questions
Chapter 12
What does this diagram show about the replication of DNA in eukaryotic cells?
Molecular Genetics
Standardized Test Practice
Chapter 12
A. DNA is replicated only at certain places along
the chromosome.
B. DNA replication is both semicontinuous andconservative.
C. Multiple areas of replication occur along the chromosome at the same time.
D. The leading DNA strand is synthesizeddiscontinuously.
Molecular Genetics
Standardized Test Practice
Chapter 12
What is this process called?
Molecular Genetics
Standardized Test Practice
Chapter 12
A. mRNA processing
B. protein synthesis
C. transcription
D. translation
Molecular Genetics
Standardized Test Practice
Chapter 12
What type of mutation results in this change in the DNA sequence?
A. deletion
B. frameshift
C. insertion
D. substitution
TTCAGG TTCTGG
Molecular Genetics
Standardized Test Practice
Chapter 12
How could RNA interference be used to treat diseases such as cancer and diabetes?
Molecular Genetics
Standardized Test Practice
Chapter 12
A. by activating genes to produce proteins that
can overcome the diseaseB. by interfering with DNA replication in cells
affected by the diseaseC. by preventing the translation of mRNA into
the genes associated with the diseaseD. by shutting down protein synthesis in the
cells of diseased tissues
Molecular Genetics
Standardized Test Practice
Chapter 12
True or False
The structure of a protein can be altered dramatically by the exchange of a single amino acid for another.
Molecular Genetics
Standardized Test Practice
Chapter 12
Molecular Genetics
Glencoe Biology Transparencies
Chapter 12
Molecular Genetics
Image Bank
Chapter 12
Molecular Genetics
Image Bank
Chapter 12
double helix
nucleosome
Molecular Genetics
Vocabulary
Section 1
Chapter 12
semiconservative replication
DNA polymerase
Okazaki fragment
Molecular Genetics
Vocabulary
Section 2
Chapter 12
RNA
messenger RNA
ribosomal RNA
transfer RNA
transcription
RNA polymerase
codon
intron
exon
translation
Molecular Genetics
Vocabulary
Section 3
Chapter 12
gene regulation
operon
mutation
mutagen
Molecular Genetics
Vocabulary
Section 4
Chapter 12
Molecular Genetics
DNA Polymerase
Transcription
Visualizing Transcription and Translat
ion
Lac-Trp Operon
Animation
Chapter 12
