3.8- THE CELL CYCLE Flashcards
Do all cells in multicellular organisms retain the ability to divide?
no
What do the cells that do not divide continuously do?
undergo regular cycle of division separated by periods of cell growth
What are the 3 stages of the cell cycle?
interphase
nuclear division
division of cytoplasm (cytokinesis)
How long is interphase in the cell cycle?
occupies most of the cell cycle
What is interphase sometimes known as?
resting phase
Why is interphase sometimes known as resting phase?
no division takes place
What is nuclear division?
when nucleus divides either into two (mitosis) or four (meiosis)
What does cytokinesis follow?
nuclear division
What is cytokinesis the process of?
cytoplasm divides to produce two new cells (mitosis) or four new cells (meiosis)
Typically, how long does it take for the complete cell cycle in a mammalian cell?
takes about 24 hours
What percentage of the cell cycle in mammalian cell cycle is interphase?
90%
What is cancer?
group of diseases (around 200 in total) caused by a growth disorder of cells
What is cancer result of?
damage to genes that regulate mitosis + cell cycle
What does damage to genes that regulate mitosis + cell cycle cause?
uncontrolled growth + division of cells
What does uncontrolled growth + division of cells form?
group of abnormal cells, called a tumour, develops + constantly expands in size
Where can tumours develop?
in any organ of the body
Where are tumours most commonly found? (8)
lungs prostate gland (male) breast ovaries (female) large intestine stomach oesophagus pancreas
How does a tumour become cancerous?
changes from being benign to malignant
How do most cells divide?
by mitosis
Why do most cells divide by mitosis? (2)
increase size of tissue during development (growth)
replace dead + worn out cells (repair)
What can the rate of mitosis be affected by? (2)
environment of cell
growth factors
What is mitosis controlled by?
two types of genes
What can a mutation in one of the two types of genes controlling mitosis do?
results in uncontrolled mitosis
In what ways can the cell be different be due to a mutation in a gene controlling mitosis?
structurally and functionally different from normal cells
What happens to most mutated cells?
most mutated cells die
What are mutated cells that survive able to do?
capable of dividing to form clones of themselves + forming tumours
Description of malignant tumours (3)
grow rapidly
less compact
more likely to be life-threatening
Description of benign tumours (3)
grow more slowly
more compact
less likely to be life-threatening
What does the treatment of cancer often involve?
killing dividing cells by blocking a part of the cell cycle
What happens as parts of the cell cycle is blocked in cancer treatment?
cell cycle disrupted + cell division + hence cancer growth ceases
What is a drug treatment for cancer?
chemotherapy
How do drugs used to treat cancer usually disrupt the cell cycle? (2)
preventing DNA from replicating
inhibiting metaphase stage of mitosis by interfering with spindle formation
What is problem of drugs used to treat cancer?
also disrupt cell cycle of normal cells
What are drugs used to treat cancer more effective against?
rapidly dividing cells
To what extent are cancer cells damaged in comparison to normal cells by drugs for cancer treatment?
damaged to a greater degree than normal cell
What is the rate of division for cancer cells?
fast rate of division
What type of normal body cell is vulnerable to damage by drugs in cancer treatment?
hair-producing cells
Why are hair-producing cells vulnerable to damage by drugs in cancer treatments?
they divide rapidly
As hair-producing cells are vulnerable to damage from drugs in cancer treatment what does this explain?
hair loss frequently seen in patients undergoing cancer treatment
