selected topics in molecular biology review session nov. 26, 2007
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Selected topics in molecular biology Review session Nov. 26, 2007. All nucleotides have a common structure. There are five principal bases in nucleic acids. Inosine is carbonylated adenosine. A, G, T, C are present in DNA A, G, U, C are present in RNA. UMP. - PowerPoint PPT PresentationTRANSCRIPT
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Selected topics in molecular biology
Review session Nov. 26, 2007
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All nucleotides have a common structure
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There are five principal bases in nucleic acids
A, G, T, C are present in DNAA, G, U, C are present in RNA
Inosine is carbonylatedadenosine
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UMP
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1) Ribonucleotide reductase catalyzes thesynthesis of deoxyribonucleotides
Inhibited by hydroxyurea, which is used as anti-cancer drug
2) Thymidylate synthase catalyzes the methylation of dUTP
Conversion of ribo-to-deoxyribonucleotides
UMP
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Anti-cancer drugsspecifically blockdTMP production
Folic acid
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Defects in the purine salvage pathway cause human diseases
Salvage PathwayActivated ribose (PRPP) + base
Nucleotides
De Novo PathwayActivated ribose (PRPP) + amino acids
+ ATP + CO2 +……….
Nucleotides
Blocked by HGPRT deficiency (Gout, Lesh-Nyhan)
PRPP
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DNA can undergo reversible strand separation
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Theeukaryoticreplication fork
Replication protein A
Replicationfactor C
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Inhibited by rifamycins(e.g., Rifampicin)
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The base pair in the 3rd codon position can “wobble”
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frameshift mutations
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Exchange of genetic material during meiosis
Recombination=crossover + exchange of DNA betweentwo DNA double strands
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Organization and rearrangement of heavy-chain DNA
V=variableD=diversityJ=joiningC=constant
VDJ recombination allows forantibody diversity
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Different classes of immunoglobulin (isotypes) fulfill different tasks
major class major class membrane- unknown against In serum in external bound parasites, secretions allergies
1st lineof defense
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Cell Cycle Control
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Multiple cdks and cyclins regulate passage of mammalian cells through the cell cycle
Restriction point is analogous to START
Cdc2/Cdk1-cyclin BCdc2/Cdk1-cyclin A
Cdk2-cyclin A
Cdk2-cyclin E
Cdk4-cyclin DCdk6-cyclin D
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good genes bad genes
proto-oncogenes oncogenesare required for promote uncontollednormal growth growth gain-of-function
mutation (can bepoint mutation, insertion or deletion)
Besides mutations in proto-oncogene/tumor suppressor coding regions, mutationsin gene regulatory elements (promoter) can deregulate the expression pattern
tumor suppressors inactive tumor suppressor
loss-of-functionmutation
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Membrane receptorsand signal
transduction cascades
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Cell-surface receptors belong to different classes
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G protein-coupled receptors contain 7 transmembrane alpha-helices
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Acetylcholine receptor in the heart muscle opens K+ channels
frequency of heartcontractions goes down