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CHAPTER 16
THE MOLECULAR BASIS
OF INHERITANCE
OUTLINE
I. DNA as the Genetic Material
A. The search for the genetic material led to DNA: science as a process
B. Watson and Crick discovered the double helix by building models to conform to X-ray
data: science as a process
II. DNA Replication and Repair
A. A. During DNA replication, base-pairing enables existing DNA strands to serve as
templates for new
complementary strands
B. .A large team of enzymes and other proteins carries out DNA replication
C. Enzymes proofread DNA during its replication and repair damage to existing DNA
D. The ends of DNA molecules pose a special function.
OBJECTIVES:
3. List the three components of a nucleotide.
- a nitrogen base, a sugar, and a phosphate.
4. Distinguish between deoxyribose and ribose.
- I already know this.
5. List the nitrogen bases found in DNA, and distinguish between pyrimidine and purine.
- Purines: Adenine and Guanine. Pyrimidines: Cytosine and Thymine.
7. Explain the "base-pairing rule" and describe its significance.
- Base-pairing pairs a certain base with its particular partner, ex adenine with thymine and
cytosine with guanine. It establishes a code for DNA.
8. Describe the structure of DNA, and explain what kind of chemical bond connects the
nucleotides of each strand and
what type of bond holds the two strands together.
- The DNA molecule is double helical and its nucleotides and strands are hydrogen bonded.
9. Explain, in their own words, semiconservative replication.
- Semi-conservative replication of DNA is when the DNA strand unzips and creates two new
identical strands, each with the template strand of the old DNA and a complementary strand of
the new DNA.
10. Describe the process of DNA replication, and explain the role of helicase, single strand
binding protein, DNA
polymerase, ligase, and primase.
- DNA replicates by unzipping into two strands that are complemented by two new strands.
Helicase is the enzyme that unwinds DNA, single strand binding protein attach to each strand of
the uncoiled DNA to help keep them separate, DNA polymerase is an enzyme that assembles the
new DNA strand, ligase connect Okazaki segments, primase initiates each complementary
segment with RNA nucleotides.
12. Define antiparallel
- A complementary strand of DNA that travels the opposite direction of its base strand.
13. Distinguish between the leading strand and the lagging strand.
- The 5’ to 3’ strand is the leading strand when created b/c it is readily done so, the 3’ to 5’ is the
lagging strand b/c it takes more time to assemble than the leading.
14. Explain how the lagging strand is synthesized when DNA polymerase can add nucleotides
only to the 3’ end.
- DNA polymerase returns to the replication fork then begins to assemble the next segment, these
segments are connected by DNA ligase which forms the complementary strand.
15. Explain the role of DNA polymerase, ligase, and repair enzymes in DNA proofreading and
repair.
- I already know this.
CHAPTER 17
FROM GENE TO PROTEIN
OUTLINE
I. The Connection between Genes and Proteins
A. The study of metabolic defects provided evidence that genes specify proteins:
science as a process
B. Transcription and translation are the two main processes linking gene to protein:
an overview
C. In the genetic code, nucleotide triplets specify amino acids
D. The genetic code must have evolved very early in the history of life
II. The Synthesis and Processing of RNA
A. Transcription is the DNA-directed synthesis of RNA: a closer look
B. Eukaryotic cells modify RNA after transcription
III. The Synthesis of Protein
A. Translation is the RNA-directed synthesis of a polypeptide: a closer look
B. Signal peptides target some eukaryotic polypeptides to specific locations in the cell
C. RNA plays multiple roles in the cell: a review
D. Comparing protein synthesis in prokaryotes and eukaryotes: a review
E. Point mutations can affect protein structure and function
F. What is a gene? revisiting the question
OBJECTIVES
4. Explain how RNA differs from DNA.
- There are 3 kinds of RNA and it is linear, while DNA has thymine it codes uracil.
5. In your own words, briefly explain how information flows from gene to protein.
- Genes become proteins through protein synthesis.
6. Distinguish between transcription and translation.
- Transcription creates RNA molecules with DNA as a template. In translation processed RNA
molecules are used to assemble amino acids into a polypeptide.
7. Describe where transcription and translation occur in prokaryotes and in eukaryotes
- Transcription occurs in the nucleus and translations occurs in the cytoplasm.
8. Define codon, and explain what relationship exists between the linear sequence of codons on
mRNA and the linear
sequence of amino acids in a polypeptide.
- Each three bases of mRNA are called a codon, these codons line up with the amino acids picked
up by the tRNA.
12. Explain the process of transcription including the three major steps of initiation, elongation,
and termination.
- Initiation: polymerase attaches to promoter regions on the DNA and begins to unzip the DNA
into 2 strands. Elongation: occurs as the polymerase unzips the DNA and assembles RNA
nucleotides using one strand of the DNA as a template. Termination: occurs when the RNA
polymerase reaches a special sequence of nucleotides that serve as a termination point.
13. Describe the general role of RNA polymerase in transcription.
- This polymerase unzips the DNA as it attaches to promoter regions.
16. Distinguish among mRNA, tRNA, and rRNA.
- mRNA provides the template used for sequencing amino acids into a polypeptide. tRNA
transfers amino acids to their proper place on the mRNA template. rRNA are the building blocks
of ribosomes.
17. Describe the structure of tRNA and explain how the structure is related to function.
- tRNA is a short RNA molecule and interactions among its various parts result in base pairing
which folds the tRNA and makes it a 3-d molecule.
18. Given a sequence of bases in DNA, predict the corresponding codons transcribed on mRNA
and the corresponding
anticodons of tRNA.
- I already know this.
21. Describe the structure of a ribosome, and explain how this structure relates to function.
- Ribosomes are formed by two subunits and has three binding sites (one for mRNA, one for
tRNA that carries a growing polypeptide chain, and one for a second tRNA that delivers the next
amino acid that will be added to the chain).
22. Describe the process of translation including initiation, elongation, and termination
- Initiation: small ribosomal subunit attaches to a special region near the 5’ end of mRNA. tRNA
carrying an amino acid (met) attaches to the mRNA. The large ribosomal subunit attaches to the
mRNA forming a complete ribosome with the tRNA. Elongation: the next tRNA binds to the A
site of the ribosome. Termination: the ribosome encounters one of the three stop codons.
26. Describe the difference between prokaryotic and eukaryotic mRNA.
- Eukaryotic mRNA molecules are processed before leaving the nucleus
27. Explain how eukaryotic mRNA is processed before it leaves the nucleus.
- The first modification adds special nucleotide sequences to both ends of the mRNA. The
second alteration occurs when some mRNA segments are removed.
29. Explain why base-pair insertions or deletions usually have a greater effect than base-pair
substitutions.
- Substitutions can be detrimental in the sense that they do not sense mutations, but insertions or
deletions disrupt codon messages downstream of the mutation.
CHAPTER 18
MICROBIAL MODELS: THE GENETICS OF
VIRUSES AND BACTERIA
OUTLINE
I. The Genetics of Viruses
A. Researchers discovered viruses by studying a plant disease: science as a process
B. A virus is a genome enclosed in a protective coat.
C. Viruses can reproduce only within a host cell: an overview
D. Phages reproduce using lytic or lysogenic cycles
E. Animal viruses are diverse in their modes of infection and of replication
F. Plant viruses are serious agricultural pests
G. Viroids and prions are infectious agents even simpler than viruses
H. Viruses may have evolved from other mobile genetic elements
II. The Genetics of Bacteria
A. The short generation span of bacteria facilitates their evolutionary adaptation to
changing environments
B. Genetic recombination produces new bacterial strains
C. The control of gene expression enables individual bacteria to adjust their metabolism
to environmental change
OBJECTIVES:
2. List and describe structural components of viruses.
-Viruses consist of a nucleic acid surrounded by a protein coat called a capsid.
3. Explain why viruses are obligate parasites.
- The only way viruses can survive is by living inside a host.
5. Explain the role of reverse transcriptase in retroviruses.
- Retroviruses use an enzyme called reverse transcriptase to make a DNA complement of their
RNA.
6. Describe how viruses recognize host cells.
- Viruses infect only a certain range of host cells, this host specificity depends on the evolution of
recognition systems by the virus.
7. Distinguish between lytic and lysogenic reproductive cycles using phage T4 and phage l as
examples.
- I already know this.
11. Explain how viruses may cause disease symptoms, and describe some medical weapons used
to fight viral infections.
- Viruses invade host cells and then destroy them when they reproduce. Vaccines are used to
fight viral infections.
12. List some viruses that have been implicated in human cancers, and explain how tumor viruses
transform cells.
- Members of the retrovirus, papovirus, adenovirus, and herpsevirus . Tumor viruses assume the
shape of cancer cells and abandon their orderly growth.
14. List some characteristics that viruses share with living organisms, and explain why viruses do
not fit our usual
definition of life.
- Viruses are able to pass on hereditary information by reproduction, it commandeers its host’s
metabolic machinery, and it is organized on a cellular level. However, it can only maintain itself
(it only comes to life) inside a host cell, by itself it is dead.
16. Describe the structure of a bacterial chromosome.
- It is a circular DNA molecule with few associated proteins
18. List and describe the three natural processes of genetic recombination in bacteria.
- Conjugation: DNA exchange between bacteria. Transduction: new DNA is introduced into a
bacteria by a virus. Transformation: bacteria absorbs DNA from their surroundings.
20. Explain how the F plasmid controls conjugation in bacteria.
- It contains the genes that enable a bacterium to produce pili.
27. Briefly describe two main strategies cells use to control metabolism.
- Lac operon breaks down lactose and Trp operon produces enzymes for the synthesis of the
amino acid tryptophan.
30. Distinguish between structural and regulatory genes.
- Structural genes contain DNA sequences that code for several related enzymes that direct the
production of some particular end product. Regulatory genes produce a repressor protein which
prevents gene expression by blocking the action of RNA polymerase.
CHAPTER 1 9
THE ORGANIZATION AND CONTROL OF
EUKARYOTIC GENOMES
OUTLINE
I. The Structure of Chromatin
A. Chromatin structure is based on successive levels of DNA packing
II. Genome Organization at the DNA Level
A. Repetitive DNA and other noncoding sequences account for much of a eukaryotic
genome
B. Gene families have evolved by duplication of ancestral genes
C. Gene amplification, loss, or rearrangement can alter a cell’s genome
III. The Control of Gene Expression
A. Each cell of a multicellular eukaryote expresses only a small fraction of its genome
B. The control of gene expression can occur at any step in the pathway from gene to
functional protein
C. Chromatin modifications affect the availability of genes for transcription
D. Transcription initiation is controlled by proteins that interact with DNA and with each
other
E. Posttranscriptional mechanisms play supporting roles in the control of gene expression
IV. The Molecular Biology of Cancer
A. Cancer results from genetic changes that affect the cell cycle
B. Oncogene proteins and faulty tumor-suppressor proteins
C. Multiple mutations underlie the development of cancer
OBJECTIVES:
1. Compare the organization of prokaryotic and eukaryotic genomes.
- Eukaryotic cells are more complexly organized than prokaryotic genomes. The control of gene
expression is also more elaborate.
2. Describe the current model for progressive levels of DNA packing.
- Histones are responsible for the first level packing of DNA in a chromatin. These beaded
strings undergo higher level packaging.
4. Distinguish between heterochromatin and euchromatin.
- Euchromatin describes regions where the DNA is loosely bound to nucleosomes. DNA in these
regions is actively being transcribed. Heterochromatin represents areas where the nucleosomes
are more tightly compacted, and where the DNA is inactive.
CHAPTER 20
DNA TECHNOLOGY
OUTLINE
I. DNA Cloning
A. DNA technology makes it possible to clone genes for basic research and commercial
applications: an overview
B. Restriction enzymes are used to make recombinant DNA
C. Genes can be cloned in recombinant DNA vectors: a closer look
D. Cloned genes are stored in DNA libraries
E. The polymerase chain reaction (PCR) clones DNA entirely in vitro
II. Analysis of Cloned DNA
A. Restriction fragment analysis detects DNA differences that affect restriction sites
B. Entire genomes can be mapped at the DNA level
III. Practical Applications of DNA Technology
A. DNA technology is reshaping medicine and the pharmaceutical industry
B. DNA technology offers forensic, environmental, and agricultural applications
C. DNA technology raises important safety and ethical questions
OBJECTIVES:
1. Explain how advances in recombinant DNA technology have helped scientists study the
eukaryotic genome.
- It allows for certain regions of the genome to be viewed at one time, also more experiments can
now be performed such as cloning for research and commercial applications.
2. Describe the natural function of restriction enzymes.
- Restriction enzymes cut up DNA at specific recognition sequences.
3. Describe how restriction enzymes and gel electrophoresis are used to isolate DNA fragments.
- Each separate DNA fragments in their own way.
7. List and describe the two major sources of genes for cloning.
- mRNA and complementary DNA.
9. Describe how "genes of interest" can be identified with the use of a probe.
- Radioactively labeled probes complement genes of interest making them easier to find.
10. Explain the importance of DNA synthesis and sequencing to modern studies of eukaryotic
genomes.
- These studies help reshape the medical and pharmaceutical industries, they provide information
for in vitro, it also offers forensic, environmental, and agricultural applications.