Cell division and cell death Flashcards
Cell cycle
Consists of interphase and mitotic phase.
Interphase
G1 phase: Physical growth (G0 phase: Inactivity).
S phase: DNA replication.
G2 phase: Preparation for division.
Mitotic Phase
M phase.
Mitosis
Cytokinesis.
DNA replication
After DNA replication each chromosome is made of two identical copies: Sister chromatids.
Two types:
Semi-conservative
Semi-discontinous
Semi-conservative (Exam)
As the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions resulting in each copy having 1 parental strand and 1 newly synthetized strand.
Semi-discontinuous (Exam)
1 strand is synthetized continuously (leading strand). The other synthetized in fragments, okazaki fragments, (Lagging strand).
How does the DNA replication work?
Helicase breaks the hydrogen bonds between the nitrogenous base pairs.
RNA primer produced by RNA primase sticks to the split DNA to start synthesis, extends from 5’ end to 3’ end.
In semi-discontinuous, the strands are replicated in opposite direction. Leading strand is replicated normally while the lagging strand can only replicate fragments (okazaki) at a time, needing multiple primers.
Exonuclease removes the RNA primers.
A specific DNA polymerase fills the gaps.
DNA ligase joins DNA fragments.
Helicase
Unwind DNA (exposing template)
Primase
Synthetize RNA primer (necessary for DNA polymerase to start)
DNA polymerase
Synthesis DNA (5’ -> 3’) Fills gaps left by RNA primers.
EXONUCLEASE
Removes RNA primers
DNA LIGASE
Closes the gaps.
Mitosis
4 phases:
- Prophase
- Metaphase
- Anaphase
- Telophase
What is the purpose of Mitosis?
Growth/repair tissue.
Replace worn out cells.
Maintainance of tissue.
What is the results of Mitosis? (Exam)
Two genetically identical diploid cells.