Cell Cycle and Cell Division Flashcards
What is a haploid cell in humans?
n
23 chromosomes
Gametes
What is a diploid cell in humans?
2n
23 Chromosome pairs
Somatic (body) cell
What are the stages in the cell cycle?
Interphase- a period of synthesis and growth
Mitosis- Formation of two genetically identical nuclei
Cytokineses- Division of cytoplasm to form two daughter cells
What are the stages in interphase?
G1 phase - growth and normal metabolic roles
S phase - DNA replication
G2 phase - growth and preparation for mitosis by organelle replication
What is the order of the stages in mitosis?
Prophase
Metaphase
Anaphase
Telophase
What’s the structure of a chromosome in prophase?
Two chromosomes joined at centromere with sister chromatids opposite each other
What occurs in interphase?
- high metabolic activity
- requires ATP
- cell increases in size
- DNA and organelles replicate
What occurs in prophase?
- chromosomes condense
- centrioles divide and move to opposite poles
- nuclear envelope disappears
- spindle forms
What occurs in metaphase?
- chromosomes line up on equator
- spindle fibres attach to centromere
What occurs in anaphase?
- spindle fibres shorten
- centromeres divide
- sister chromatids separate
- each is pulled to opposite side of the cell
What occurs in telophase?
- chromosomes uncoil and lengthen
- spindle breaks down
- nuclear envelope reforms
- nuclear division is complete
How does the spindle differ in plant and animal cells?
In animal cells the spindle degenerates at telophase
In plant cells the spindle remains throughout new cell wall formation
Where does mitosis occur in plant and animal cells?
Animal cells:
Epithelia, bone marrow, gut lining
Plant cells:
Meristems
How does cytokineses occur in animal cells?
The construction of the parent cell creates a cleavage furrow dividing the cell from the outside inwards
How does cytokineses occur in plant cells?
Droplets of cell wall material form a cell plate across the equator from the inside outwards to extend and join to create a new cell wall
Where are centrioles found?
In animal cells but not plants
Why does mitosis give genetic stability?
It maintains the chromosome number by producing genetically identical daughter cells
How is mitosis used for growth?
It increases cell number and can also be used to repair tissue and replace dead cells
What is asexual reproduction?
Produces genetically identical offspring
Takes place in unicellular organisms (yeast, bacteria) and some plants and tubers (strawberries)
How can the cell cycle be affected?
By damage to the genes which control it
Through radiation, chemicals and viruses which may stop division or cause uncontrollable division
What happens when cells divide uncontrollably?
Tumors such as cancers are formed
How are tumours controlled?
Tumour suppressing genes
What are proto-oncogenes and what do they become?
They are genes that have the potential to cause cancer and when they mutate they become oncogenes
