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Unformatted text preview: 4% areaxeneeaeeeaasaae' anearsae ‘ 118% : 468 as sas/ a 1. Many genes are essential during embryonic development and in the adult stage. Gene targeting is a powerful method to study the function of a gene by modifying
the physical structure of the gene such that its function is knocked out. How can
the function of an essential gene required for embryonic development be studied
in an adult knockout mouse? (5%) . What experimental evidence supports the ﬂuid mosaic model of biomembranes? ' Certain integral membrane proteins are signiﬁcantly less mobile than others. What
accounts for this reduced mobility? (5%) . Translation of proteins across the membrane of the endoplasmic reticulum (ER) is usually studied using microsomes, which are vesicles derived from the ER
membrane during isolation. Microsomes from the rough ER carry ribosomes
attached to their outer surface. Translation of proteins across microsomal
membrane can be assessed by several experimental criteria: (1) protection of the
newly synthesized protein from exogenously added proteases, and lack of protection from proteascs when detergents are present to solubilize the protecting lipid bilayer; (2) glycosylation of newly synthesized proteins by oligosaccharide
transferases, which are localized exclusively to the lumen of the ER; (3) cleavage
of signal peptides by signal peptidase, which is also active only on the luminal
side of the ER membrane. You have performed protein synthesis by translation of
a puriﬁed mRNA with microsomes. You then treated the translation reactions in
four different ways: (1) no treatment, (2) add a protease, (3) add a protease and
detergent, and, (4) disrupt microsomes and add endoglycosidase H (endo H),
which removes N-linked sugars that are added in the ER. An electrophoretic
analysis of these samples is shown below. Microeomee Mdorosomee Treatment
Absent Present protease
endo H as anaaxeweeaaaaaaaaaa
Ha - ﬁﬁ=468
a 3 Hag 2: E Is the protein of interest a glycoprotein? Why? Explain the migration of the proteins in lanes 5, 6, and 8. Is the protein of interest a transmembrane protein?
Why? (10%) . Explain embryonic and adult stem cells= respectively. What are the advantages and
disadvantages of working with embryonic and adult stem cells with respect to
stem—cell therapies in humans? (5%) 5. Answer the questions about eukaryotic mRNA (10%)
a. Name the three general posttranscriptional processing reactions that are
observed in eukaryotic mRNA.
b. What protein domain is essential to couple these processes with
c. Describe the function of the structure present on the 5’ and 3’ ends of mature
eukaryotic mRNA in translation initiation. d. In addition to the coding region, the mature rnRNA contains 5’ and 3’
untranslated regions. What is their function? 6. A transcription factor named TF was investigated. Please explain the underlined
terms. (15%) a. TF contains leucine zipper and basic amino acid domains. b. Its activation domain was mapped. c. The ﬂ—TF fusion protein was expressed in eukaryotic cells to demonstrate
its subcellular localization. CI. The expression of TF in cells was knocked down by a speciﬁc siRNA. e. The cells were transfected with the plasmid encoding FLAG-tagged TF and
the in vivo DNA—binding activity of TF was analyzed by chromatin- -immunoprecipitation assay. 7 Recent researches have implicated Z—DNA and quadruplex DNA in life processes.
Brieﬂy describe (a) how these variant forms of DNA can form in the middle of a
section of B—DNA, and (b) the physiological roles they may play (3%). Brieﬂy describe the physiological roles of (a) DNA gyrase in prokaryotic cells, (b)
proliferating cell nuclear antigen (PCNA), (c) replication factor C and (d)
telomerase in eukaryotic cells (10%). lama ﬂirt. no on as ensnxeneeaesanaeaaa ﬂaﬁﬂﬁﬁ¥itb$ 7‘“? ‘ 468
. _ as 3 ﬂag 3 E 9 How can breakdowri in DNA repair play a role in the development of human
cancers (3%)? 10 Each of the following pairs of primers has a problem if used in the polymerase
chain reaction. Tell why the primers would not work well. (a) Forward primer 5’
GCCCTCCGGAGACCCCATTGG 3’, Reverse primer 5'
TTCTAAGAAAAACTGTTAAGG 3’ (b) Forward primer 5’
TCGAATTGCCAATGAAGGTCCG 3’, Reverse primer 5’
CCTTCATTGGCAATTCGAGCCAT (4%). 11 Autophagy is a process in which cytoplasmic components are broken down by the
cell from inside. Please discuss the possible roles of this phenomenon. (5%) 12. In the plasma membrane of mammalian cells, phospholipids are not uniformly
distributed between the two monolayers. Please describe the patterns of different
phospholipids found in each monolayer. (5%) 13. An asymmetric cell division produces two daughter cells with different properties.
Please give an example of this event and discuss the consequence of this event.
(5%) 14. What are hydropathy curve and its application? (5%) 15. Which organelle has its own DNA? How does this relate to maternal genetics?
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