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
Selected topics in molecular biology
Review session Nov. 26, 2007
All nucleotides have a common structure
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
UMP
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
Anti-cancer drugsspecifically blockdTMP production
Folic acid
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
DNA can undergo reversible strand separation
Theeukaryoticreplication fork
Replication protein A
Replicationfactor C
Inhibited by rifamycins(e.g., Rifampicin)
The base pair in the 3rd codon position can “wobble”
frameshift mutations
Exchange of genetic material during meiosis
Recombination=crossover + exchange of DNA betweentwo DNA double strands
Organization and rearrangement of heavy-chain DNA
V=variableD=diversityJ=joiningC=constant
VDJ recombination allows forantibody diversity
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
Cell Cycle Control
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
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
Membrane receptorsand signal
transduction cascades
Cell-surface receptors belong to different classes
G protein-coupled receptors contain 7 transmembrane alpha-helices
Acetylcholine receptor in the heart muscle opens K+ channels
frequency of heartcontractions goes down