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Chapter Sixteen
List the three components of a nucleotide.
 Sugar, Phosphate, Base (A, T, G, C)
Distinguish between deoxyribose and ribose.
 Deoxyribose is the five-carbon sugar in DNA and ribose is the five-carbon sugar
in RNA.
List the nitrogen bases found in DNA, and distinguish between pyrimidine and purine.
 Adenine, Guanine, Cytosine, and Thymine are the bases. Adenine and Guanine
are Purines (larger) and Cytosine and Thymine are pyrimidine (smaller).
Explain the "base-pairing rule" and describe its significance.
 Bases complement each other. Adenine with Thymine and Guanine with
Cytosine. If bases form specific pairs, the information on one strand
complements that along the other.
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.
 DNA is a double helix. Purine and pyrimidine bases are stacked. There are ten
layers of nitrogenous base pairs in each turn of the helix. Hydrogen bonds hold
the bases together.
Explain, in their own words, semiconservative replication.
 They predicted that when a double helix replicates, each of the two daughter
molecules will have one old or conserved strand from the parent molecule and
one newly created strand.
Describe the process of DNA replication, and explain the role of helicase, single strand
binding protein, DNA polymerase, ligase, and primase.
 The DNA double helix opens and a replication fork spreads in both directions
away from the central initiation point. Enzymes called DNA polymerases catalyze
synthesis of a new DNA strand. New nucleotides align themselves along the
templates of the old DNA strands. Primers are short segments of RNA
polymerized by an enzyme called primase. Helicases are enzymes that catalyze
unwinding of the parental double helix to expose the template. Single-strand
binding proteins are proteins that keep the separated strands apart and stabilize the
unwound DNA until new complementary strands can be synthesize.
Define antiparallel.
 The two sugar-phosphate backbones of the helix were antiparallel; that is, they
ran in opposite directions.
Distinguish between the leading strand and the lagging strand.
 Leading strand - The DNA strand that is synthesized as a single polymer in the 5’
– 3’ direction towards the replication fork.
 Lagging strand - The DNA strand that is produced as a series of short segments.
Explain how the lagging strand is synthesized when DNA polymerase can add
nucleotides only to the 3’ end.
DNA polymerase removes the RNA primer and replaces it with DNA. DNA ligase
catalyzes the linkage between the 3’ end of each new Okazaki fragment to the 5’ end of
the growing chain.
Explain the role of DNA polymerase, ligase, and repair enzymes in DNA proofreading
and repair.
 In bacteria, DNA polymerase proofreads each newly added nucleotide against its
template. Any incorrectly paired nucleotide, the enzyme removes and replaces it
before continuing with synthesis. In eukaryotes, additional proteins as well as
polymerase participate in mismatch repair. The damaged segment is excised by
one repair enzyme and the remaining gap is filled in by base-pairing nucleotides
with the undamaged strand. DNA polymerase and DNA ligase are enzymes that
catalyze the filling-in process.
Chapter Seventeen
Explain how RNA differs from DNA.
 RNA is a single strand. The five-carbon sugar in RNA nucleotides is ribose rather
than deoxyribose. The nitrogenous base uracil is found in place of thymine.
In your own words, briefly explain how information flows from gene to protein.
 DNA transcribes into RNA and then RNA is translate depending where it’s sent.
Distinguish between transcription and translation.
 Transcription is the synthesis of RNA using DNA. Translation is from RNA to a
polypeptide.
Describe where transcription and translation occur in prokaryotes and in eukaryotes.
 In eukaryotes transcription occurs in the nucleus and the translation occurs in the
cytoplasm. In prokaryotes both occur in the cytoplasm since there is a lack of a
nuclei.
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.
 Nucleotide triplets in mRNA are called codons. They specify which amino acid
will be added to a growing polypeptide or which signals termination.
Explain the process of transcription including the three major steps of initiation,
elongation, and termination.
 RNA synthesis on a DNA templates is catalyzed by RNA polymerase. It follows
the same base pairing rule as DNA replication except that in RNA uracil
substitutes for thymine. Promoters, specific nucleotide sequences at the start of a
gene signal the initiation of RNA synthesis. Proteins help eukaryotic RNA
polymerase recognize promoter sequences. Transcription continues until a
particular RNA sequence signals termination.
Describe the general role of RNA polymerase in transcription.
 RNA polymerase transcribe genes. RNA polymerases bind to DNA at the
initiation site.
Distinguish among mRNA, tRNA, and rRNA.
 Messenger RNA copies the info stored in the strand of DNA. Ribosomal RNA
makes up the ribosomes. Transfer RNA shuttles amino acids to the site of protein
synthesis.
Describe the structure of tRNA and explain how the structure is related to function.
 A tRNA molecule has a 4 leaf clover structure. One end carries an amino acid the
other (anticodon) has 3 nitrogenous bases that match the codon in the mRNA.
Like enzymes they attach to an animo acid in the cytoplasm and shuttles it to the
ribosome.
Given a sequence of bases in DNA, predict the corresponding codons transcribed on
mRNA and the corresponding anticodons of tRNA.
 DNA=TAC mRNA=AUG tRNA=UAC
Describe the structure of a ribosome, and explain how this structure relates to function.
 I already know this from a previous chapter.
Describe the process of translation including initiation, elongation, and termination.
 An initiator tRNA activates translation. Additional amino acids are linked to its
neighboring amino acid. When a codon codes for stop, termination occurs.
Describe the difference between prokaryotic and eukaryotic mRNA.
Explain how eukaryotic mRNA is processed before it leaves the nucleus.
 In RNA splicing, introns (non-coding regions) are removed and exons (coding
regions) join.
Explain why base-pair insertions or deletions usually have a greater effect than base-pair
substitutions.
 Because mRNA is read as a series of triplets during translation, insertion or
deletion of nucleotides may alter the reading of the genetic message. The
nucleotides following the insertion or deletion to be improperly grouped into
codons.
Chapter Eighteen
List and describe structural components of viruses.
 Genome may be Double-stranded DNA, Single-stranded DNA, Double-stranded
RNA, Single-stranded RNA, Organized as single nucleic acid molecule, Either
linear or circular, May have as few as 4 genes to as many as several hundred.
Capsid has a Protein coat and Encloses viral genome. It’s shape may be Rodshaped, polyhedral, Complex. Its Composed of many protein subunits, Made from
one or a few types of proteins. The Envelope is a Membrane that cloaks some
viral capsids. Helps virus infect its host. Derived from host cell membrane.
Usually virus-modified containing proteins & glycoproteins of viral origin.
Bacteriophage capsids.
Explain why viruses are obligate parasites.
 They can only reproduce inside a cell.
Explain the role of reverse transcriptase in retroviruses.
 Transcribes DNA from RNA template
Describe how viruses recognize host cells.
 That each type of virus has a characteristic host range, determine by specific
receptors on a host cell.
Distinguish between lytic and lysogenic reproductive cycles using phage T4 and phage l
as examples.
 In the Lytic cycle, injection of a phase genome into a bacterium programs
destruction of host DNA, production of new phages and digestion of the host's
cell wall, releasing the progeny phages. In a Lysogenic cycle, a temperate phage
insets its genome into the bacterial chromosome as a phage, which is passed on to
host daughter cells until it is stimulated to leave the chromosome and initiate a
Lytic cycle.
Explain how viruses may cause disease symptoms, and describe some medical weapons
used to fight viral infections.
 Viruses may damage or kill cells - infected cell may cause lysosomes to release
hydrolytic enzymes. Be toxic themselves or cause infected cells to produce toxins.
Cause varying degrees of cell damage depending upon regenerative ability of
infected cells Weapons against viral infections: Vaccines-harmless variant or
derivative of pathogenic microbe. Antiviral drugs- (1) some interfere with viral
nucleic acid synthesis. (2) Mechanism for some effective drugs is unknown
List some viruses that have been implicated in human cancers, and explain how tumor
viruses transform cells.
 Retrovirus (Leukemia), Herpes virus (Burkitt's lymphoma), Papovavirus (Cervical
cancer), Hepatitis B virus (Chronic hepatitis / Liver cancer).
Some tumor viruses transform cells by activating cellular oncogenes, usually
more than one oncogene must be activated to transform cell.
List some characteristics that viruses share with living organisms, and explain why
viruses do not fit our usual definition of life.
 Viruses either have DNA or RNA, which is essential for reproduction. But, in
every organism except viruses they have DNA and RNA, that's why scientist are
not sure what to classify viruses.
Describe the structure of a bacterial chromosome.
 The bacterial chromosome is a circular DNA molecule with few associated
proteins. Because bacteria has short life span, they are able to reproduce rapidly.
List and describe the three natural processes of genetic recombination in bacteria.
 Transformation, naked DNA enters the cell from the surroundings. In
transduction, bacterial DNA is carried from one cell to another by phages. In
conjugation, an F-factor containing "male" cell transfers DNA to an F-cell.
(Bacterial Sex.)
Explain how the F plasmid controls conjugation in bacteria.
Briefly describe two main strategies cells use to control metabolism.
 The control of gene expression enables individual bacteria to adjust their
metabolism to environmental change
Distinguish between structural and regulatory genes.
 A structural gene is a gene that codes for a polypeptide. A regulatory gene
transcription of the regulatory gene produces an mRNA molecule that is
translated into the repressor protein, which can then reach by diffusion.
Chapter Nineteen
Compare the organization of prokaryotic and eukaryotic genomes.
 Eukaryotic genomes are more complexly organized than prokaryotic genomes.
The control of gene expression is also more elaborate in eukaryotes than in
prokaryotes. In particular, selective control of genes is required for cellular
differentiation.
Describe the current model for progressive levels of DNA packing.
 Chemical modification o relocation of DNA within a genome can alter gene
expression.
Distinguish between heterochromatin and euchromatin.
 Heterochromatin is a nontranscribed eukaryotic chromatin that is so highly
compacted that it is visible with a light microscope during interphase.
Euchromatin- the more open unraveled form of eukaryotic chromatin, which is
available for transcription.
Chapter Twenty
Explain how advances in recombinant DNA technology have helped scientists study the
eukaryotic genome.
 Because of the new technology, scientists are able to manipulate and analyze
genetic material. They already knows what gene goes where, now its only a
matter of time where they can fix or alter a genetic disorder.
Describe the natural function of restriction enzymes.
 Restriction is the process where foreign DNA is cut into small pieces
Describe how restriction enzymes and gel electrophoresis are used to isolate DNA
fragments.
 Have sticky ends (single-stranded ends). Sticky ends used in lab to join DNA
pieces from different sources. Gel electrophoresis Used to separate restriction
fragments, Separates pieces based on size through electrical field, Bigger
fragments travel slower through gel, Smaller fragments travel faster, Produces
pattern of bands of DNA of different lengths.
List and describe the two major sources of genes for cloning.
 Bacterial plasmids, Foreign DNA of interest
Describe how "genes of interest" can be identified with the use of a probe.
 Probe single-stranded DNA, Complementary to fragments of markers, Probe
attaches to fragment markers
Explain the importance of DNA synthesis and sequencing to modern studies of
eukaryotic genomes.
 Uses of DNA technology in basic research (Can be used to find segments of
DNA, Can be used to study details of eukaryotic gene, Can be used to map
eukaryotic chromosomes, Can be used to mass produce proteins used in research).
Human genome project (Map human genome, Locate disease genes). Medical
uses (Diagnosis of diseases, Human gene therapy, Vaccines, Drug production insulin & erythropoietin (stimulates RBC production)). Forensic uses - DNA
fingerprinting and Agricultural uses