topic 2 cells and control Flashcards
What is the cell cycle?
- A series of events that take place in a cell involving cell growth, DNA replication 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 the new organelles and DNA replication 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?
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
outline metaphase
chromosomes line up along cell equator
outline anaphase
spindle fibres attach to each chromosome and 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
what is cancer
uncontrolled cell division results in formation of a tumour (mass of cells)
What does the 95th percentile mean?
What does the 95th percentile mean?
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 can doctors determine from percentile charts?
● 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 than in younger animals as growth stops 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?
unspecialized cells from which differentiated cells develop
what is meant by differentiation
● The process by which stem cells become specialised (have a specific function)
Why is cell differentiation important?
Enables the formation of specialised tissues with specific functions e.g. muscle tissue
What are embryonic stem cells?
Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
