Name:______Date:______Period:____

Chapter 12 Overview

Ch. 12 Notes Page 1

Section 1: DNA: The Genetic Material

Section 2: Replication of DNA

Section 3: DNA, RNA, and Protein

Section 4: Gene Regulation and Mutation

Ch. 12 Notes Page 1

Note: 1869 - Frederick Miescherdiscovered DNA, was acidic molecule in nucleus; called it
NUCLEICACIDS.

12.1 DNA: The Genetic Material

Fredrick Griffith

  • Performed the first major experiment that led to the discovery of DNA as the ______

–The First demonstration of bacterial ______.

–Experiments done by Frederick Griffith (in London) in 1928 found there were two different types of the bacterium Streptococcus pneumoniae:

•An "S" or ______coat strain, which is lethal to mice.

•An "R" or ______strain, which will not hurt the mouse.

–Griffith found that he could heat ______the smooth strain.

–However, if he were to take a mixture of the heat-inactivated S strain, mixed with the R strain, the bacteria would die.

–Thus there was some material in the ______S strain that was responsible for "transforming" the R strain into a lethal form.

–Fredrick 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 ______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.

Oswald Avery

  • Identified the molecule that transformed the R strain of bacteria into the S strain
  • Concluded that when the S cells were killed,______
  • R bacteria incorporated this ______into their cells and ______into S cells.

Hershey and Chase (1952)

  • Used ______labeling to trace the DNA (P) and protein (S)
  • Concluded that the ______DNA was injected into the cell and provided the genetic information needed to produce new viruses

12.1 Table Summary of Hershey-Chase Results

Group 1 Viruses labeled with 32P / Group 2 Viruses labeled with 35S
Infected Bacteria / Liquid with Viruses / Infected Bacteria / Liquid with Viruses

Chargaff’s rule: C = G and T = A

  • In 1950, Erwin Chargaff analyzed the base composition of DNA in a number of organisms. Purines = ______; Pyrimidines = ______
  • 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 ______candidate for the genetic material than protein.

X-ray Diffraction Structure Analysis (1951-1952)

  • X-ray diffraction data helped solve the structure of DNA
  • Indicated that DNA was a ______
  • This is the famous ______- Picture 51 which is believed to have been leaked to James Watson and Francis Crick by Maurice Wilkins.

X-ray Diffraction Rosalind Franklin (1920 - 1958)

  • The technique with which Maurice Wilkins and Franklin set out to do this is called ______.
  • 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 ______very carefully, it is possible to reconstruct the ______of the atoms in the molecules that comprise the basic unit of the crystal.
  • Rosalind Franklin died from ______in April of 1958, at the age of 37.

James Watson and Francis Crick 1953

  • Built a model of the double helix that conformed to the others’ research
  • two outside strands consist of alternating ______and ______
  • ______and ______bases pair to each other by three hydrogen bonds
  • ______and ______bases pair to each other by two hydrogen bonds

Nobel Prize in Medicine/Physiology

•The rules of the Nobel Prize forbid posthumous nominations; because ______had died in 1958 she was not eligible for nomination to the Nobel Prize subsequently awarded to Francis ______, James ______, and Maurice ______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 ______at Cambridge and Watson had worked on ______for some years.

DNA Structure – Double Helix

  • DNA often is compared to a twisted ladder.
  • Rails of the ladder are represented by the alternating ______and phosphate.
  • The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

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′.

Chromosome Structure

  • DNA coils around ______(proteins) to form ______, which coil to form chromatin fibers.
  • The chromatin fibers supercoil to form ______that are visible in the metaphase stage of mitosis.

12.2 Replication of DNA

Semiconservative Replication

  • Parental strands of DNA separate, serve as ______, and produce DNA molecules that have ______of parental DNA and______of new DNA.

Unwinding

  • ______, an enzyme, is responsible for unwinding and unzipping the double helix.
  • ______, an enzyme, adds a short segment of RNA, called an ______

______, on each DNA strand. Keeping the DNA strands separate.

Base pairing

  • DNA polymerase (an enzyme) continues adding appropriate nucleotides to the chain by adding to the 3′ end of the new DNA strand.
  • One strand is called the ______and is elongated as the DNA unwinds.
  • Leading Strand is synthesized ______

  • The other strand of DNA, called the ______, elongates away from the replication fork.
  • The ______is synthesized discontinuously into small segments, called Okazaki fragments

Joining

  • ______removes the RNA primer and fills in the place with DNA nucleotides.
  • ______links the two sections.

Write a summary of replication in your own words

Comparing DNA Replication in Eukaryotes and Prokaryotes

  • Eukaryotic DNA unwinds in multiple areas as DNA is ______.
  • In ______, the circular DNA strand is opened at one origin of replication.

12.3 DNA, RNA, and Protein

Central Dogma: ______

RNA

  • Contains the sugar ribose (instead of deoxyribose) and the base uracil (instead of thymine)
  • Usually is single stranded
  • Three kinds: messenger RNA, transfer RNA, and Ribosomal RNA
  • ______(mRNA)

a)Long strands of RNA nucleotides that are formed complementary to one strand of DNA

b)Carries genetic information from DNA in the ______to direct protein synthesis in the ______

2. ______(rRNA)

  • Associates with proteins to form ribosomes in the cytoplasm

3. ______(tRNA)

  • Smaller segments of RNA nucleotides that transport amino acids to the ribosome where proteins are made by adding one______at a time

Transcription

  • Through ______, the DNA code is transferred to mRNA in the nucleus.
  • DNA is unzipped in the ______and RNA polymerase binds to a specific section where an mRNA will be synthesized

RNA Processing

The code on the DNA is interrupted periodically by sequences that are not in the final mRNA.

  • Intervening sequences are called ______– these are ______.
  • Remaining pieces of DNA that serve as the ______sequences are called ______.

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 ______.

The 1968 Nobel Prize in Medicine was awarded to Robert W. Holley, Har Gobind Khorana, and Marshall W. Nirenberg for deciphering the Genetic Code. The code is used by cells to translate messenger RNA sequences into protein. The mRNA sequence is read three bases at a time in codons.Each ______identifies a specific ______or a ______.

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 ______.
  • Each anticodon is______to a codon on the mRNA.

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.

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 ______is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway
  1. ______
  2. ______
  3. ______
  4. ______

The Trp Operon

The Lac Operon

Eukaryote Gene Regulation

  • Controlling transcription
  • ______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.

Hox Genes

Hox genes are responsible for the general body pattern of most animals.

RNA Interference

RNA interference can stop the mRNA from translating its message.

Mutations -A permanent change that occurs in a cell’s DNA is called a mutation.

Types of mutations

  • Point mutation
  • Insertion
  • Deletion
  • Frameshift

Protein Folding and Stability

Substitutions also can lead to genetic disorders. Can change both the folding and stability of the protein

Causes of Mutation

  1. Can occur spontaneously
  2. Chemicals and radiation also can damage DNA.
  3. High-energy forms of radiation, such as X rays and gamma rays, are highly ______.

Body-cell (Somatic) v. Sex-cell Mutation

______mutations are not passed on to the next generation.

Mutations that occur in ______are passed on to the organism’s offspring and will be present in every cell of the offspring.

Review Questions

  1. Which scientist(s) definitively proved that DNA transfers genetic material?
  2. Name the small segments of the lagging DNA strand.
  3. Which is not true of RNA?

Which is true:

  1. The experiments of Avery, Hershey and Chase provided evidence that the carrier of genetic information is ______.
  2. What is the base-pairing rule for purines and pyrimidines in the DNA molecule?

What are the purine bases ______

What are the pyrimidine bases ______

  1. What are chromosomes composed of?
  2. The work of Watson and Crick solved the mystery of how DNA works as a genetic code. True or False
  3. Which is not an enzyme involved in DNA replication?
  4. During DNA replication, what nucleotide base sequence is synthesized along an original strand that has the sequence TCAAGC?
  5. Which shows the basic chain of events in all organisms for reading and expressing genes?
  1. In the RNA molecule, uracil replaces ______.
  2. What does each diagram shows?
  1. What characteristic of the mRNA molecule do scientists not yet understand?
  1. Why do eukaryotic cells need a complex control system to regulate the expression of genes?
  1. Which type of gene causes cells to become specialized in structure in function?
  2. What is an immediate result of a mutation in a gene?
  3. Which is the most highly mutagenic?
  4. Look at the following figure. Identify the proteins that DNA first coils around.
  5. Explain how Hox genes affect an organism.
  1. Explain the difference between body-cell and sex-cell mutation.
  2. What does this diagram show about the replication of DNA in eukaryotic cells?
  3. What is this process called?

  1. What type of mutation results in this change in the DNA sequence? TTCAGG TTCTGG
  1. How could RNA interference be used to treat diseases such as cancer and diabetes?
  1. The structure of a protein can be altered dramatically by the exchange of a single amino acid for another. True or False

Ch. 12 Notes Page 1