2.6 Cell divison and organisation Flashcards
What stages are in the cell cycle?
Gap 1 phase
G1checkpoint
S phase
Gap 2 phase
G2 checkpoint
M phase
What does the M phase involve?
Mitosis and cytokinesis
What parts of the cell cycle happen in interphase?
All but M Phase
so G1 G1 checkpoint S G2 G2 checkpoint
What happens in G1 phase?
Cell growth and new organelles and proteins are made.
What happens at G1 checkpoint?
The cell checks for any damage to FNA and checks chemicals needed for replication are present.
What happens in the S phase?
Cells DNA replicates.
What happens in G2 phase?
Cell keeps growing and more proteins for cell division are made.
What happens in the G2 checkpoint?
The cell checks DNA has been replicated with no damage. If no damage allows cell to enter mitosis
What happens during interphase ?
Cell carries out normal functions and prepares to divide. DNA unravels and replicates. Organelles replicate and extra ATP produced.
What stages are in Mitosis?
Prophase , Metaphase , Anaphase, Telophase.
What happens in Prophase?
Chromosomes condense and centrioles move to poles of cell forming spindle fibres.
Nuclear envelope breaks down.
What happens during metaphase?
Chromosomes line up along middle of cell. (M for middle).
The chromosomes attach to the spindle fibres at there centromeres.
Then a metaphase checkpoint occurs where they check for all chromosomes being attached to spindle fibres before mitosis can continue
What happens during Anaphase?
Centromeres divide and separate sister chromatids. Spindle fibres contract pulling chromatids to centromeres at poles.
What happens during Telophase?
Chromatids reach poles and uncoil to become chromosomes again. New nuclear envelopes form around each group of chromosomes.
What happens during cytokinesis?
The cytoplasm divides by forming a cleavage furrow.
What does mitosis produce?
Two diploid genetically identical daughter cells.
What does meiosis produce?
four haploid genetically different daughter cells.
Produces gametes
What is diploid and haploid
diploid = has 2 chromosomes (a pair)
Haploid = only 1 chromosome (half)
What are the stages in Meiosis?
Interphase
Meiosis 1 with prophase metaphase anaphase telophase + cytokinesis
Meiosis 2 with prophase 2 metaphase 2 anaphase 2 telophase 2 + cytokinesis
How is genetic variation in gamete’s produced/ made?
- Crossing over of chromatids
- Independent assortment of chromosomes
How does crossing over of chromatids create genetic variation?
The chromatids twist around each other in cell division and bits of chromatid swap over. They contain the same genes but now have different alleles.
Where does crossing over occur?
In prophase 1 of meiosis 1.
How does independent assortment cause genetic variation?
When the homologous pairs of chromosomes line up in metaphase 1 and separate its random which chromosome from each pair ends up in which daughter cell.
When does independent assortment occur?
During Metaphase 1 of meiosis 1
What is a stem cell?
An unspecialised cell. They have the ability to develop into different types of cell.
What stems cells do humans have?
Embryonic stem cells.
Adult stem cells found in bone marrow .
What is differentiation?
When cells divide to become new ones and become specialised.
What do adult stem cells mainly do?
Replace worn out blood cells (erythrocytes rbc or neutrophils wbc)
What stem cells do plants have and what do they specialise into?
Stem cells found in meristem and can divide to become xylem and phloem sieve tubes in the roots
What are 3 examples of specialised cells in animals? Explain there structure
- erythrocytes - biconcave shape so large surface area, No nucleus so more room for haemoglobin.
- Neutrophils - Flexible shape so can engulf stuff, Lots of lysosomes to break down engulfed stuff.
- Epithelial cells- Have interlinking membranes, have cilia or microvilli to increase SA.
what is a tissue?
A group of cells that are specialised to work together to carry out a particular function. It can have more then one type of cell
What are examples of animal tissues?
- squamous epithelium
- Muscle tissue
- Cartilage
- Ciliated epithelium
what are examples of plant tissues?
- Xylem tissue.
- Phloem tissue.
What is an organ?
A group of different tissues that work together to perform and particular function.
What is an organ system?
Organs that are working together to form a system.
What is mitosis used for?
Growth, tissue repair, asexual reproduction.
What is mitosis used for?
Growth
replacing worn out cells
repairing damaged tissues
reproduction asexually
