Transcript Document

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
Conversion of ribo-to-deoxyribonucleotides
1) Ribonucleotide reductase catalyzes the
synthesis of deoxyribonucleotides
Inhibited by hydroxyurea, which is used as anti-cancer drug
2) Thymidylate synthase catalyzes the
methylation of dUTP
UMP
Anti-cancer drugs
specifically block
dTMP production
Folic acid
Defects in the purine salvage
pathway cause human diseases
Salvage Pathway
Activated ribose (PRPP) + base
Blocked by HGPRT deficiency
Nucleotides (Gout, Lesh-Nyhan)
De Novo Pathway
Activated ribose (PRPP) + amino acids
+ ATP + CO2 +……….
Nucleotides
PRPP
DNA can undergo reversible strand
separation
Replication protein A
Replication
factor C
The
eukaryotic
replication fork
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 between
two DNA double strands
Organization and rearrangement of
heavy-chain DNA
V=variable
D=diversity
J=joining
C=constant
VDJ recombination allows for
antibody diversity
Different classes of immunoglobulin
(isotypes) fulfill different tasks
1st line
of defense
major class
In serum
major class
in external
secretions
membranebound
unknown
against
parasites,
allergies
Cell Cycle Control
Multiple cdks and cyclins regulate passage
of mammalian cells through the cell cycle
Cdc2/Cdk1-cyclin B
Cdc2/Cdk1-cyclin A
Cdk4-cyclin D
Cdk6-cyclin D
Cdk2-cyclin A
Restriction point is
analogous to START
Cdk2-cyclin E
good genes
proto-oncogenes
are required for
normal growth
bad genes
oncogenes
promote uncontolled
growth
gain-of-function
mutation (can be
point mutation,
insertion or deletion)
tumor suppressors
loss-of-function
mutation
inactive tumor
suppressor
Besides mutations in proto-oncogene/tumor suppressor coding regions, mutations
in gene regulatory elements (promoter) can deregulate the expression pattern
Membrane receptors
and 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 heart
contractions goes down