Download CHAPTER 10: The Structure and Function of DNA

CHAPTER 10: The Structure and Function of DNA
Why This Chapter Matters
1. Hereditary information is stored in the chemical language of DNA.
2. DNA directs the biochemical, cellular, anatomical, and physiological activities of the human body.
3. Scientists can manipulate the DNA of cells to modify the traits of crops, transform the characteristics
of cells, and treat and potentially prevent disease.
4. Viruses play a key role in the history of molecular biology and continue to be important pathogens in
humans, bacteria, plants, and animals.
5. Treatments and cures for viral infections are likely to be the products of research into molecular
biology.
B: Learning Objectives for Chapter 10 in Textbook (see lecture objectives below)
Biology and Society: Tracking a Killer
1. Explain how flu vaccines are produced and why flu vaccines are important.
DNA: Structure and Replication
2. Explain what was and was not known about DNA by the early 1950s.
3. Describe and compare the chemical compositions of DNA and RNA.
4. Describe the key features of the overall shape of a DNA molecule. Explain how Watson and
Crick determined the structure of DNA.
5. Describe the process of DNA replication.
The Flow of Genetic Information from DNA to RNA to Protein
6. Define transcription and translation. Explain why the hypothesis “one gene-one enzyme” is not
correct.
7. Explain how the language of DNA directs the production of polypeptides.
8. Explain how codons are used to construct polypeptides. Explain what the authors mean when they
state “there is redundancy in the code but no ambiguity.”
9. Describe the steps of transcription and the processing of RNA before it leaves the nucleus.
10. Compare the structures and functions of mRNA, tRNA, and rRNA.
11. Describe in detail the process of translation.
12. Distinguish between insertion, deletion, and substitution mutations. Explain how mutations can be
harmful or beneficial to organisms.
Viruses and Other Noncellular Infectious Agents
13. Compare the lytic and lysogenic cycles of bacteriophages.
14. Compare the life cycles of RNA and DNA viruses. Describe the spread, symptoms, and prevention of
viral diseases in plants and animals.
15. Describe the reproductive cycle of retroviruses such as HIV and the mechanisms by which AZT and
protease inhibitors limit AIDS.
16. Explain how viroids and prions cause disease.
Evolution Connection: Emerging Viruses
17. Describe the three processes that contribute to the emergence of viral disease.
Key Terms
adenine (A)
AIDS
bacteriophages
cap
codon
cytosine (C)
DNA
DNA polymerase
double helix
emerging viruses
exons
genetic code
guanine (G)
HIV
introns
lysogenic cycle
lytic cycle
messenger RNA
molecular biology
mutagen
mutation
nucleotide
phages
polynucleotide
prion
promoter
prophage
provirus
retrovirus
reverse transcriptase
ribosomal RNA (rRNA)
RNA polymerase
RNA splicing
start codon
stop codon
sugar-phosphate backbone
tail
terminator
thymine (T)
transcription
transfer RNA (tRNA)
translation
uracil (U)
virus
Word Roots
muta = change; gen = producing (mutagen: a physical or chemical agent that causes mutations)
phage = eat (bacteriophages: viruses that attack bacteria)
poly = many (polynucleotide: a polymer of many nucleotides)
pro = before (prophage: phage DNA inserted into the bacterial chromosome before viral replication)
retro = backward (retrovirus: an RNA virus that reproduces by first transcribing its RNA into DNA
then inserting the DNA molecule into a host’s DNA)
trans = across; script = write (transcription: the transfer of genetic information from DNA into an
RNA molecule)
LECTURE OBJECTIVES FOR CHAPTERS 10: DNA Structure and Function
1. Explain why proteins were thought to be the cell's genetic material. Was this a logical
hypothesis? Was this a correct hypothesis? What is the "tempting template hypothesis"
and who is Johann Frederick Miescher (1868)? Compare the terms nuclein, chromatin, and
DNA. (class notes)
2. Describe the results of P.A. Levine's research on the biochemistry of DNA. State the two
major conclusions he reached? (class notes)
3. Define “nucleotide” and explain why nucleotides are important.
4. Explain Griffith's experiments in which he discovered "transforming factor." What was
the significance of these experiments?
5. Explain what significant information O.T. Avery contributed to our understanding of
transforming factor.
6.
Explain what Escherichia coli (E. coli), phages, and bacteriophages are. Name the two
scientists considered the fathers of bactriophage research, prepare a simple sketch of
the structure of a bactriophage, and explain why bacteriophages are so useful in studying
DNA.
7. Explain the experiments of Hershey and Chase. What did they show? Did their work
support the findings of Oswald Avery or the deduction of P. A. Levine?
8. State the results of Chargaff's experiments on the ratios of the four types of nucleotides
in the DNA of various species of life. Compare this with the findings of P. A. Levine. (see
table below, they are not in your textbook)
Chargaff's Results, 1952
COMPARISON OF BASE RATIOS OF THE DNA OF SEVERAL SPECIES
Source
Human being
Ox
Salmon sperm
Wheat germ
E. coli bacteria
Sea urchin
adenine(A)
30.4%
29.0%
29.7%
28.1%
24.7%
32.8%
guanine (G)
19.6%
21.2%
20.8%
21.8%
26.0%
17.7%
cytosine (C)
19.9%
21.2%
20.4%
22.7%
25.7%
17.3%
thymine (T)
30.1%
28.7%
29.1%
27.4%
23.6%
32.1%
9. Explain what X-ray diffraction is and state how the X-ray diffraction studies of Wilkins
and Franklin contributed to our understanding of the structure of the DNA molecule.
10. State at least four characteristics that DNA, or any other molecule, must exhibit if it is
to, indeed, be the genetic code of life.(class notes)
1. It must carry genetic information from cell to cell and from generation to generation.
It must carry a great amount of information.
2. It must carry information to copy itself and be able to do so with great precision.
3. BUT... it must also make mistakes sometimes (mutate). Mistakes (mutations) must then
be copied as faithfully as the original. Without the capacity of the genetic molecule to
copy its mistakes, there could be no evolution by natural selection.
4. There must be some mechanism for decoding the stored genetic information and
translating it into action in the living cell.
11.
List five significant pieces of data known by Watson and Crick as they began their
attempt to discover the molecular structure of DNA. (class notes)
1. The DNA molecule known to be a very large, long, and very thin molecule composed of
four sub-units: adenine nucleotides, guanine nucleotides, cytosine nucleotides and thymine
nucleotides.
2. Levine thought these nucleotides were arranged in repeating units of four-"tetranucleotides" and thought the molecule was therefore pretty uninteristing=boring!
3. Linus Pauling had shown that protein molecules were often great large helices, and
suggested that DNA may also be a helix.
4. Wilkin's and Franklin's X-ray diffraction photos showed patterns that very strongly
suggested that DNA was helical.
5. Chargaff's data, which contradicted Levine's, suggested that A=T and C=G.
12. Describe the Watson/Crick model of the structure of DNA.
13. Define: replication, DNA polymerase, and semi conservative replication.
14. Describe the structure of a eukaryotic chromosome by defining the following terms and
explaining their relationship to each other: chromosome, gene, histone proteins,
chromatin. How many of each or the following are found in HUMAN cells? chromosomes,
genes, bases, inches of uncoiled DNA, feet of uncoiled DNA
OBJECTIVES FOR CHAPTER 14: GENE FUNCTION: RNA AND PROTEIN SYNTHESIS
1. Explain why "making proteins" is so important to cells.
2. Outline the flow of genetic information in cells from DNA to protein. (“the central dogma
of biology.)
DNA ------------transcription------------RNA---------translation----------PROTEIN
.
3. Explain what a gene is. How many genes are found in each human cell? How many
chromosomes are found in each human cell? Describe the relationship between
nucleotides, genes, chromosomes, and DNA?
4. Explain what DNA triplets are and how they are related to the genetic code, amino acids
and proteins.
5. List three differences between the molecular structure of DNA and mRNA and compare
mRNA and tRNA anddescribe the function of each of these four molecules.
6. Define and compare the terms replication, transcription, and translation.
7. List the base-pairing rules that apply to DNA and mRNA for transcription.
8. Compare the following pairs: mRNA/tRNA; triplet/codon; codon/anticodon;
anticodon/amino acid attachment site (of tRNA).
9. Describe in detail how DNA directs the construction of proteins in a cell. Prepare a
diagram like the one passed out in class to help you summarize this process.
10. List the three terminator codons. (UAA, UAG, UGA)
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11. Be able to answer questions like the ones below:
a. If a strand of mRNA reads UUUUCACGCGGUGGGGUUCCCCAACCGGACAUUUGGAAAUAA,
what polypeptide does it stand for?
If a gene (DNA) reads CAGAGTAATAGGTACCATTAGGGAAAAGACACT,
what polypeptide does it stand for?
b. A polypeptide hormone from the pituitary gland, oxytocin, which causes the uterus to
contract during childbirth, has the following amino acid sequence:
cys-tyr-phe-glu-asn-cys-pro-arg-gly.
Write a possible base sequence for the mRNA which translates for this polypeptide and a
possible base sequence for the gene which codes for this polypeptide.
c. Disregarding initiators and introns but NOT terminators; how many bases are in the gene
for a protein of 100 amino acids; how many codons are in the mRNA for a protein which is
composed of 82 amino acids; insulin is composed of two polypeptides, one of 21 amino acids
and one of 30 amino acids, how many bases are in each of the genes for the two subunits
of insulin?
12. Define the term mutation and explain the possible effects of mutations on protein
synthesis. List three types of mutations (additions, deletions, substitutions). Define the
terms spontaneous mutation and mutation rate.
Key Investigators
Freidrich Meischer
P.A.T. Levine
Frederick Griffith
O.T. Avery
Hershey and Chase
Salvador Luria and Max Delbrϋck
Erwin Chargaff
James Watson and Francis Crick
Maurice Wilkins and Rosalind Franklin