Cell Division and Growth Flashcards
What is the cell cycle?
● A series of events that take place in a cell
involving cell growth, DNA replication and
cell division
● It is described as the lifecycle of a cell
State the three stages of the cell cycle
Stage 1 - interphase
Stage 2 - mitosis
Stage 3 - cytokinesis
What is interphase?
The longest stage of the cell cycle that
involves cell growth, the synthesis of
new organelles and DNA replication
What does DNA replication involve?
● Double helix ‘unzips’ exposing two strands
● DNA bases align next to complementary bases on
the DNA strands
● Complementary base pairs join
● Two identical DNA molecules formed
What is a chromosome?
A linear DNA molecule tightly coiled
around proteins
What happens to chromosomes during DNA
replication?
The DNA in the ‘arm’ of each
chromosome (chromatid) is
replicated.
What is mitosis?
A form of cell division that produces two
diploid ‘daughter’ cells, both genetically
identical to the parent cell
Why is mitosis important in organisms?
● Asexual reproduction
● Growth
● Repair of damaged cells
● Cell replacement
State the four stages of mitosis
● Prophase
● Metaphase
● Anaphase
● Telophase
Outline prophase
● DNA condenses, chromosomes become visible
● Nuclear membrane disappears
-spindle fibres form
Outline metaphase
● Chromosomes line up along the cell equator
Outline anaphase
● Spindle fibres attach to each chromosome
● ‘Arms’ of each chromosome pulled to opposite poles
● Chromatids separated
Outline telophase
● Nucleus of the cell divides
● New membrane forms around each set of
chromosomes
What does cytokinesis involve?
● Division of the cell membrane and cytoplasm
● Two genetically identical ‘daughter’ cells
produced
A cell divides by mitosis once every 2 minutes.
Calculate the number of identical cells present after
10 minutes
10 ÷ 2 = 5
5 cell divisions have taken place
2^5 = 32 cells
What is cancer?
● Non-communicable disease
● Uncontrolled cell division (due to damaged DNA) results
in the formation of a primary tumour
● Tumour cells break off and spread to other tissues
forming secondary tumours
What are percentile charts?
● A chart used to monitor growth
● Measurements (e.g. fetal length or head
circumference) can be compared to the expected
values at a certain age
What does the 95th percentile mean?
95% of measurements will be below the
value of the 95th percentile
How do percentile charts demonstrate how you are growing?
● Slower growth than normal (below the bottom line)
● Faster growth than normal (above the top line)
● Abnormal growth (irregular growth patterns)
Describe growth in animals
● Cell division occurs in all body cells.
● It occurs at a slower rate in adults that in younger animals as growth stops in adulthood and cell division is only required for replacement and repair.
● Most cells differentiate at an early stage and become
specialised.
● Some adult stem cells retain their ability to differentiate.
Describe growth in plants
● Cell division can only occur in meristematic tissue.
● The rate of cell division remains the same throughout a plant’s life.
● Meristematic stem cells can differentiate into any cell type for as long as the plant lives
● Cell elongation occurs in all cells. Cells expand and enlarge enabling growth of the plant.
What are stem cells?
Cells that are unspecialised and capable
of differentiating into a range of different
cell types
What is meant by ‘differentiation’?
● The process by which stem cells become
specialised (have a specific function)
● Some genes switch on or off, determining cell
type
Why is cell differentiation important?
It enables the formation of specialised
tissues with specific functions e.g.
muscle tissue.
