CELL DIVISION Flashcards
(25 cards)
Interphase.
G1- Produces proteins and replicates organelles.
S- DNA synthesised and proof reading enzymes check for mutations.
G2- Growth.
MITOSIS- Prophase.
- Chromatin fibres shorten and condense into chromosomes.
- Centrioles move to opposite poles and spindle fibres attach to centromeres.
Metaphase.
- Spindle fibres move chromosomes to equator of cell (Metaphase plate).
Anaphase.
- Spindle fibres contract and pull chromatids by their centromeres to the opposite poles.
Telophase.
- Nuclear envelope forms around chromosomes.
- Chromosomes uncoil.
- 2 Diploid cells formed.
Cytokinesis - Plants.
- No cleavage furrow formed (Cell wall).
- Vesicles from Golgi apparatus form at equator.
- Vesicles fuse with each other and the cell membrane which splits the cell.
- Cell wall forms.
Cytokinesis - Animals.
- Cleavage furrow forms in middle of the cell.
- Cell surface membrane pulled towards middle by cytoskeleton till it fuses together creating 2 cells.
Functions of mitosis.
- Growth.
- Repair.
MEIOSIS - 1.
P- Chromosomes shorten and thicken, Spindle fibres form, Crossing over, Homologous chromosomes form bivalents.
M- Bivalents line up across equator.
A- Chromosomes pulled to opposite poles.
T- 2 nuclear envelopes form.
MEIOSIS - 2.
P- Spindle fibres form, Centrioles replicate and move to opposite poles.
M- Chromosomes line up along equator.
A- Chromatids pulled to opposite poles.
T- 4 nuclear envelopes form, 4 non-identical daughter cells formed, 4 haploid cells.
Increasing variation in meiosis.
- Crossing over of bivalents.
- Random alignment / independent assortment of bivalents and chromosomes.
- DNA mutations.
- Random fertilisation.
Crossing over.
- During Prophase 1 of meiosis.
- Homologous chromosomes pair up.
- Chromatids cross over forming a chiasmata.
- Swaps alleles between chromosomes to produce different combinations.
Random alignment / independent assortment of bivalents.
- During Metaphase 1, pairs of homologous line up along the equator.
- It is completely random where the maternal and paternal chromosome lines up.
- Ends in a random chromosomes in the daughter cell.
Levels of organisation.
- Cells (Erythrocytes, neutrophils, and palisade cells), Tissues (Epithelium, cartilage, and xylem tissue), Organs (Stomach, pancreas, and leaf), Organ systems (Cardiovascular system, digestive system, and root system).
Animal tissues.
- Squamous epithelium.
- Ciliated epithelium.
- Cartilage.
- Muscle.
Squamous epithelium.
- Thin lining for many organs such as the lungs.
- One cell thick.
- Gases can diffuse quickly.
Ciliated epithelium.
- Cilia - Sweeps mucus containing pathogens away.
- Goblet cells secrete mucus.
Cartilage.
- Connective tissue between bones.
- Provides support for organs such as ears + nose.
- Made up of chondrocyte cells + extracellular matrix.
Muscle.
- Made up of bundles of elongated cells (muscle fibres).
- Contract + relax.
- 3 types =
1. Smooth = In walls of organs.
2. Cardiac = Found in the heart.
3. Skeletal = Found attached to bones.
Plant tissues.
- Xylem.
- Phloem.
Xylem.
- Movement of water + ions within plants.
- Hollow tube (no cytoplasm, organelles, end walls) - forms a continuous column for water to flow through.
- Strengthened and waterproof by ligninified walls.
- Non-lignified pits for water to move out into plant.
Phloem.
- Transport of sugars and amino acids within plants.
- Columns of sieve tube elements and companion cells.
- STE separated by Sieve plates with holes so sugars can pass through.
- Very few organelles so sugars can pass through easily.
- Companion cells contain many mitochondria to release energy.
Specialised cells.
- Stem cell that has differentiated.
- Have features that enable them to carry out specific functions.
Specialised animal cell examples.
- Erythrocytes.
- Neutrophils.
- Sperm cells.
- Squamous epithelial cells.
- Ciliated epithelial cells.
