Cell division Flashcards
What are the 3 parts of interphase?
G1, S, G2
What happens in G1?
Organelles replicate
Cell grows in size
What happens in S?
DNA is replicated in the nucleus
What happens in G2?
Energy stores are increased
Cell continues to grow in size
What is checked at the G1 checkpoint?
- Cell size
- Nutrients
- Growth factors
- DNA damage
What is checked at the G2 checkpoint?
- Cell size
- DNA replication
- DNA damage
What is G0?
Where the cell leaves the cycle
What are 3 common reasons why cells enter G0?
The cell has differentiated
The cell is old
The cell is damaged
What are senescent cells?
Old cells that stop dividing
What is cytokinesis?
Where the cytoplasm divides and two cells are produced
What is the spindle assembly check point?
Where it is checked that all chromosomes are attached to spindle fibres and aligned
What is the spindle assembly check point also known as?
The metaphase checkpoint
What would the indefinite replication of cells lead to?
Increased frequency of mutation = increased likelihood of harmful mutation
What does mitosis produce?
Two identical daughter cells
How are chromatids produced?
When a chromosomes is converted into two identical chromatids
What is the centromere?
The centre point where two chromatids join to form a chromosome
What are the four stages of mitosis?
Prophase, Metaphase, Anaphase and Telophase
What happens to the nucleolus during prophase?
It disappears
What do chromatin fibers do during prophase?
Coil and condense to form chromosomes
What happens in animal and but not plant cells during prophase to do with centrioles?
Centrioles move to opposite poles of the cell
What has happened by the end of prophase?
The nuclear envelope has disappeared
What happens during metaphase?
Chromosomes line up along the metaphase plate equator
What is the metaphase plate?
The (invisible) line through the centre of the cell, where chromosomes line up (during metaphase)
What happens during anaphase to centromeres?
Centromeres holding the chromatids together in each chromosomes divide
What happens to chromatids in anaphase?
The chromatids are separated by the shortening of spindle fibres, and are pulled to opposite poles of the cell
What happens during telophase?
Two new sets of chromosomes gather at each pole of the cell
The nuclear envelope reforms around these two groups of chromosomes
The chromosomes begin to uncoil and the nucleolus is formed
What happens in cytokinesis in animal cells?
- Cleavage furrow forms around the middle of the cell
- Cytoskeleton pulls cell surface membrane inwards until it is close enough to fuse around the middle, forming two cells
What happens in cytokinesis in plant cells?
Vesicles gather along the middle of the cell, and fuse with one another and the cell surface membrane to form two separate cells
What are homologous chromosomes?
Chromosomes from different parents that are similar and pair up together
Overview of meiosis 1
Reduction division- the pairs of homologous chromosomes are separated into two cells- each will contain 23 chromosomes
Overview of meiosis 2
Similar to mitosis- the pairs of chromatids present in each cell are separated, forming two more cells (4 total overall)
What is haploid?
A cell with 23 chromosomes
What is the main thing that occurs in prophase 1 of meiosis?
Crossing over, where genes are swapped between homologous chromosomes
What is formed from crossing over?
Bivalents
What is the main thing that occurs in metaphase 1 of meiosis?
Homologous chromosomes line up in pairs along the metaphase plate- independent assortment occurs
What is independent assortment?
The orientation and location of each homologous pair on the metaphase plate equator is random and independent of any other homologous pair, meaning there are many different combinations that can occur
What does independent assortment and crossing over result in?
Genetic variation
What are the main difference between anaphase 1 in meiosis and anaphase in mitosis?
In anaphase of mitosis, chromatids are pulled to opposite poles, whereas in meiosis 1, homologous chromosomes are pulled to opposite poles
What happens in telephase 1 of meiosis?
The nuclear membrane reforms around the different sets of chromosomes
The cell undergoes cytokinesis
What are the 4 final products of meoisis?
4 non-identical daughter cells
What is meiosis 2 very similar to?
Mitosis
