Question 1. List the following items in order of size from the smallest to largest:

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• Question 1. List the following items in order of
  size from the smallest to largest
• A. Nucleosome smallest__C_____
• B. Mitochondrion __A_____
• C. Diameter of a DNA molecule Largest__B_____

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• Question 2. Give experimental evidence to support
  that DNA, and not protein, is a genetic material.
• See experiments by Griffiths and Avery et al. on
  R and S strains of Streptococcus pneumoniae
  Figs. 5-3 and 5-4 or
• Experiment by Hershey and Chase on T2 virus
  infecting E. coli cell Fig. 5-5.

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Griffiths experiment regarding DNAs
characteristics.
Fig. 5-3, p. 173
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Fig. 5-4 DNA is genetic material (Avery et al.).
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Is the genetic material protein or DNA?Hershey
and Chase expt. (Fig. 5-5, p. 174)
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• Question 3. Fill in the blanks
• Disulfide bonds can form between two cysteine
  side chains in proteins.
• The 5end of RNA is capped by the addition of
  7-methylguanosine .
• Nucleotides are joined together by phosphodiester
  linkage between 5and 3 carbon atoms to form
  nucleic acids.

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• Question 4. Short answers.
• A. Cholesterol comprises up to 50 of membrane
  lipids in many animal cells. Explain in no more
  than two sentences why it is not possible to form
  lipid bilayers with cholesterol alone.
• Membranes are stabilized by phospholipids which
  are strongly amphipathic, that is with very
  strong hydrophilic (charged, both () and (-) as
  well as with polar groups) and very strong
  hydrophobic hydrocarbon chains of 12-22 carbons
  in length. Cholesterol is not sufficiently
  amphipathic to form a stable bimolecular leaflet
  in which the only hydrophilic group is the
  hydroxyl, with is only weakly polar. The rest of
  the molecule is completely hydrophobic.

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Question 4. Short answers.

• b. RNA splicing is considered an important rather
  than a wasteful process? Explain.
• RNA splicing makes genetic recombination between
  exons of different genes more likely, leading to
  formation of different mRNAs and evolution of
  genes for new proteins.

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• Question 5. Briefly describe the
  structure-function relationship for each of the
  following terms
• A. Small nuclear ribonucleoprotein particles The
  snRNPs are special kind of enzymes which are
  composed of a complex of proteins and RNA. They
  catalyze removal of introns from RNA (RNA
  splicing). Different types of snRNPs recognize
  different regions of introns by complemetary
  base-pairing (e.g. U1 snRNP recognize 5splice
  site).

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• b. Aminoacyl-tRNA synthetases are the enzymes
  with two binding sites, one for a specific amino
  acid and the other for a specific tRNA. These
  enzymes catalyze the ATP-mediated covalent
  coupling of an amino acid to its appropriate set
  of tRNA molecules.

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• c. Lysosomes Lysosomes have a number of
  hydrolytic enzymes e.g. proteases which function
  at acidic pH and cause hydrolysis of
  macromolecules. Low pH in lysosme is maintained
  by influx of proton by H-ATPase pumps on
  lysosome membrane.

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Transcription of two genes seen be EM Fig. 7-8

• Where are Polymerases?
• Where are transcription start/stop sites?
• Where are the 3 and 5 ends of the transcript?
• Which direction are the RNA polymerases moving?
• Why are the RNA transcripts so much shorter than
  the length of the DNA that encodes them?
• See Figs. 7-9 and 7-17 for answer to this
  question.

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• Question 7 Write a short essay on the biological
  information flow (DNA ? RNA ? protein) in
  eucaryotes.
• The essay should contain these points Fig.
  7-20
• Transcription of a gene by RNA polymerase (Fig.
  7-9)
• mRNA processing e.g. 5 RNA capping, splicing, 3
  polyadenylation Figs. 7-12, 7-17
• mRNA transport to cytosol Fig. 7-19
• precise role of genetic code, tRNA, ribosomes,
  mRNA in translation Figs. 7-26, 7-32.

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• Question 8. Which of the following statements are
  correct? Explain your answers.
• Lipids in a lipid bilayer do not rotate rapidly
  around their long axis.
• Lipids in a lipid bilayer do not flip flop
  readily from one lipid monolayer to the other.
• Glycolipids move through different
  membrane-enclosed compartments during their
  synthesis but remain restricted to one side of
  the lipid bilayer.
• See question 11-9 and its answer in your text
  book (Pages 387, A30)

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Problem Solving Shown in the table below are the
sequences of selected amino acids from different
types of human hemoglobin (abbreviated Hb). Some
forms of hemoglobin are defective, while others
are not. From what you know about protein
structure, explain why Sickle Cell and
Hammersmith Hbs are defective while delta Hb is
not. Amino acid number Type of Hemoglobin (Hb)
3 4 5 6.. 9... 40 41 42
43 Normal beta Hb Leu Thr Pro Glu Ser Gln Arg
Phe Glu Sickle Cell Hb (defective) Leu Thr Pro
Val Ser Gln Arg Phe Glu Hammersmith Hb
(defective) Leu Thr Pro Glu Ser Gln Arg Ser
Glu Normal delta Hb Leu Thr Pro Glu Thr Gln
Arg Phe Glu
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Acid side chains-negatively charged
Panel 2-5, p75
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Panel 2-5, p75
Polar side chains-interact well with water, can
form H-bonds
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Panel 2-5, p75
Nonpolar groups-energetically unfavorable for
them to contact water