Cell Division Flashcards
(19 cards)
What is DNA coiled around?
Histones. During interphase this exists as chromatin.
What happens when preparing for nuclear division?
The chromosomes are copied so each half of the chromosome is a chromatid
Chromatids are joined by a centromere
What does diploid mean?
Two identical sets of chromosomes
What does haploid mean?
One set of each pair of chromosomes
This will be in gametes
What is the interphase?
G1 phase:
The number of organelles increase and the volume of cytoplasm also increases
-Chromosomes are checked for damage. If detected, the cycle will not continue until repaired
Synthesis:
DNA is replicated. There are now identical copies of each chromosomes.
Another check is done to ensure all DNA was replicated. If not the cell cycle will be stopped
G2 phase:
Structures directly involved in mitosis are formed.
The DNA is checked for errors again. If detected the cell will attempt to repair
Outline the processes in mitosis
1) Prophase:
The chromatin condses and coils into chromosomes. The chromosomes consist of two identical chromatin joined by a centromere.
Centrioles move to poles and microtubules radiate out. The nuclear envelope then dissapears
2) Metaphase:
The spindle fibres move the chromosomes to the centre of the cell.
Another cell check will occur to see if chromosomes attached to spindle fibres correctly
3) Anaphase:
The cebtromere is divided and chromosomes are pulled apart to opposite poles
4) Telophase:
Spindle fibres dissappear and chromosomes rehydrate and uncoil. A new nuclear envelope and nucleolus forms
Explain cytokenesis in animal cells
A ring of microfilaments contract which pinches the cell in the middle, causing a cleavage furrow to form. This then separates to produce two identical daughter cells
Explain cytokenisis in plant cells
Vesicles containing cell wall material collect along the centre of the cell which forms a cell plate made of pectin. A cellulose cell wall is then laid down on both sides, creating the cell membrane leaving some plasmodesmata
What is meiosis?
Nuclear division which reduces the chromosomes by half, meaning its haploid. This results in four haploid daughter cells
Describe the process of meiosis
1) Prophase I:
Nucleolus and nuclear envelope dissappear. Centrioles divide and form spindles.
Chromosomes coil and condense.
There are four chromatids in each pair of Chromosomes.
Crossing over then occurs where proportions of the opposite chromatids swap. Where this happens is called a chiasma.
2) Metaphase 1:
Homologous pairs line up at the equator
3) Anaphase 1:
Spindle fibres pull one of each pair to opposite ends. Independent assortment occurs which produces genetic variation
4) Telophase 1:
The nuclear envelope reforms and cytokenisis occurs.
Meiosis 2 is the same as mitosis
What is mitosis for?
Growth and repair
Replace damaged cells
Cloning
What is meiosis for?
Produces variation
Helps adapt
Evolution
New combinations of genes
What is a tissue?
A group of similar cells that work together
What is an organ
A collection of tissues working together to perform a specific function
What are stem cells?
Unspecialised cells which can divide and differentiate repeatedly by mitosis to form either more stem cells or specialised cells.
Where are stem cells found in plants?
Meristem tissue
E g in vascular bundles cambium cells can divide and differentiate into phloem or xylem cells
What are the types of stem cells
1) Totipotent stem cells:
They can divide and differentiate into any cells and form whole new organisms
2) Plutipotent:
Can form cells and tissues but cannot form whole new organisms
3) Multipotent:
Can only form specific cells
What cells can bone marrow produce?
-Platelets
-White blood cells
-Red blood cells
What can stem cells do in medicine?
-Treat neurological disorders
-Repair damaged tissue
