Lecture 4 - Cellular Aspects of Development – the Cell Cycle and Cell Division Flashcards
what is the definition of the cell cycle?
The process that cells undergo to duplicate their contents to pass on to two identical daughter cells
This involves both DNA replication and duplication of cellular constituents such as endoplasmic reticulum, mitochondria etc. and their separation into two daughter cells
what are the 2 stages of the cell cycle?
1) Cell replication
2) Cell division (also known as cytokinesis)
what is the cell cycle important for?
This process is fundamental to ALL LIVING ORGANISMS and common to both prokaryotes (bacteria) and eukaryotes (yeast, plants and animals).
what is the prokaryotic cell cycle?
-Divides 20-40 minutes – very fast
-Continuous cell growth and DNA replication
-“random” segregation of DNA between cells – 99.9% accurate
Genome relatively simple
Small (5-100 kb) and circular
1) Cleavage of DNA to produce three prime end
2) Synthesis of RNA primer for DNA polymerase
3) Proteins required – e.g. type II topoisomerase
what is the eukaryotic cell cycle?
Cell cycle times
Yeast = 2 hours
Humans = 24 hours
has interface then mitosis
what is interface?
split into 3 parts such as G1 then S (DNA synthesis) then G2
each of the gaps are control points
what happens during the m stage?
mitosis which is chromosome separation then cytokinesis
what is DNA synthesis?
VERY precise process - only once per cell cycle and the cell has to get it exactly right
Far more complex!
Humans have 23 chromosomes ~100 Mb
1,000 – 10,000s of genes. All very IMPORTANT!
One copy per daughter cell
what is the ORC?
Origin Replication complex
Complex of proteins
Drive DNA replication
Including cdc18
What are the stages of mitosis?
During interphase DNA not visible
Called “de-condensed”
1 Prophase - Centrioles duplicate, Centrioles move to poles, Chromosomes condense, Mitotic spindle forms
2 Metaphase - Chromosomes move to equator of cell
3 Anaphase - Daughter chromatids separate and move to poles
4 Telophase - Telophase Membranes form around new nuclei
what is abscission?
cytokinesis
