文档介绍：Chapter 7 Micromolecules and Molecular ics
The key informational macromolecules in prokaryotic and eukaryotic cells are DNA, RNA, and protein.
Molecular ics deals with the mechanisms by which the information in DNA is replicated, and by which it can be transcribed into RNA and translated into specific proteins.
Central Dogma of Molecular Biology 中心法则
One-way transfer
of ic information
from nucleic acid
to protein is call
Central Dogma of
Molecular Biology
Information Transfer in Prokaryotes and Eukaryotes
Prokaryotes
Eukaryotes
DNA Replication
Complementary base pairing
Semiconservative
Template and primer
From 5’-phosphate to the 3’-hydroxyl end
DNA polymerase and ligase
A short stretch of RNA serves as a primer
Primase: a specific RNA-polymerizing enzyme
Initiation of DNA synthesis
1. Origin of replication:
300 bases with specific
sequence;
2. DNA double helix
opens up at the origin of
replication
3. Replication fork (left)
4. Bidirectional replication
structure in
circular DNA
6. Single eukaryotic
chromosome has many
origins
7. Replication is carefully
regulated.
DNA replication process
1. Leading strands: 5’-P 3’-OH
2. Lagging strands: 5’-P RNA 3’-OH
3. DNA polymerase I, II, III
Leading and Lagging Strands
Leading strand: DNA synthesis occurs
continuously from the 5’-phosphate to
the 3’-hydroxyl;
Lagging strand: DNA synthesis occurs
discontinuously.
Enzymes in lagging strand synthesis:
DNA primase, DNA polymerase III
and I, DNA ligase
Okazaki
Fragment
Enzymes in lagging strand
synthesis:
DNA primase,
DNA polymerase III and I,
DNA ligase
Proofreading: DNA polymease III has 3’ 5’ exonuclease activity