Cell cycle, mitosis and stem cells Flashcards
What are centrioles made of? What do two centrioles form?
- centrioles are made of hollow fibres known as microtubules
- two centrioles at right angles to each other form a centrosome which organises the spindle fibres during cell division
What are microtubules?
- microtubules are filaments of protein that can be used to move substances around inside a cell, as well as to support the shape of a cell from the inside
What is chromatin? Where is it contained?
- the nucleus contains chromatin, the material from which chromosomes are made
- chromosomes are made of sections of linear DNA tightly wound around proteins called histones
What is cytoplasmic division?
cytoplasmic division is cytokinesis which is division of the cytoplasm to form two new cells
When does DNA replication occur in the cell cycle?
- DNA replication occurs during interphase (the synthesis phase aka the S phase)
- DNA replicates itself during the S phase of the cell cycle so that each daughter cells has a copy of the DNA after cell division
What are the three phases of the cell cycle?
- interphase
- nuclear division (mitosis)
- cell division (cytokinesis)
What do cyclins trigger?
- the movement from one phase to another is triggered by chemical signals called cyclins
What happens during interphase? What are the three phases that interphase consists of?
- During interphase, the cell increases in mass and size and carries out its normal cellular functions (e.g. synthesising proteins and DNA replication ready for mitosis)
interphase consists of three phases (in this order): - G1 phase
- S phase
- G2 phase
What happens during the G1 phase? When does it lead to the S phase? (interphase)
- at some point during the G1 phase a signal is received telling the cell to divide again
- the DNA replicates (resulting in each chromosome consisting of two identical sister chromatids)
- this phase of the interphase is called the S phase
- the S stands for synthesis (of DNA) (the S phase is relatively short)
What is the gap between the previous cell division and the S phase called?
- the gap between the previous cell division and the S phase is called the G1 phase - G stands for gap
- cells make the RNA, enzymes and other proteins required for growth during the G1 phase
What occurs between the S phase and next cell division event?
- between the S phase and next cell division event, the G2 phase occurs
What happens during the G2 phase?
- during the G2 phase, the cell continues to grow and the new DNA that has been synthesised is checked and errors are usually repaired
- other preparations for cell division are made (e.g. production of tubulin protein, which is used to make microtubules for the mitotic spindle)
What is the difference between the cell cycle and mitosis?
- the cell cycle is the process by which a cell grows and divides into two daughter cells
- mitosis is a type of cell division in which one cell divides to produce two new cells that are genetically identical to itself
When does nuclear division happen? What happens in nuclear division (mitosis)?
- it follows interphase
- referred to as the M phase -M stands for mitosis
- cell growth stops during the M phase
When does cytokinesis happen? What happens in cytokinesis? What is involved in cytokinesis in animal cells and plant cells?
- follows the M phase
- (aka cytoplasmic division)
- once the nucleus has divided into two genetically identical nuclei, the whole cell divides and one nucleus moves into each cell to create two genetically identical daughter cells
- in animal cells, cytokinesis involves constriction of the cytoplasm between the two nuclei and in plant cells (they do not undergo this constriction) a new cell wall is formed (plant cells synthesise a new cell plate between the two new cells)
