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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.

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Selected topics in molecular biology

Review session Nov. 26, 2007



There are five principal bases in nucleic acids
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



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
Defects in the purine salvage pathway cause human diseases

Salvage Pathway

Activated ribose (PRPP) + base

Blocked by HGPRT deficiency

(Gout, Lesh-Nyhan)

Nucleotides

PRPP

De Novo Pathway

Activated ribose (PRPP) + amino acids

+ ATP + CO2 +……….

Nucleotides


Dna can undergo reversible strand separation
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”



Exchange of genetic material during meiosis

Recombination=crossover + exchange of DNA between

two DNA double strands


Organization and rearrangement of heavy chain dna
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 major class membrane- unknown against

In serum in external bound parasites,

secretions allergies



Multiple cdks and cyclins regulate passage of mammalian cells through the cell cycle
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

Restriction point is

analogous to START

Cdk2-cyclin A

Cdk2-cyclin E


good genes bad genes cells through the cell cycle

proto-oncogenes oncogenes

are required for promote uncontolled

normal growth growth

gain-of-function

mutation (can be

point mutation,

insertion or deletion)

tumor suppressors inactive tumor

suppressor

loss-of-function

mutation

Besides mutations in proto-oncogene/tumor suppressor coding regions, mutations

in gene regulatory elements (promoter) can deregulate the expression pattern


Membrane receptors cells through the cell cycle

and signal

transduction cascades



G protein-coupled receptors contain cells through the cell cycle

7 transmembrane alpha-helices


Acetylcholine receptor in the heart muscle cells through the cell cycle

opens K+ channels

frequency of heart

contractions goes down


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