Cell division

Cell division

Occurs in the nucleus of eukaryotic cells by mitosis and meiosis

Replacement of the entire lining of your small intestine

Liver cells only divide for repairing

Nerve cells do not divide

Chromosomes

Long and thin for replication and decoding

Become short and fat prior mitosis → easier to separate due to compact form

Meiosis (reduction division)

During the production of sex cells (gametes) in animals

In spore formation which precedes gamete production in plants

Haploid gametes (sperm ovum) - sexual reproduction

DNA in a cell replicates only once, but cell divides twice

The Cell Cycle

Interphase

G1: Protein synthesis and growth (10 hours)

Preparation for DNA replication (e.g. growths of mitochondria)

Differentiation, only selected genes are used to perform different functions in each cell

S: DNA Replication (9 hours)

G2: short gap before mitosis, organelles and proteins for mitosis are made (4 hours)

G0: Resting phase (nerve cells)

M-phase

Mitotic division of the nucleus (Prophase, Metaphase, Anaphase, Telophase)

Cytokinesis (division of the cytoplasm)

Interphase

Phase with highest metabolism (mitochondria have a high activity)

Muscles never complete the whole cycle

Mitosis

Process of producing 2 diploid daughter cells with the same DNA by copying their chromosomes (clones)

Chromosomes can be grouped into homologous pairs

Mitosis occurs in

Growth

Repair

Replacement of cells with limiting life span (red blood, skin cells)

Asexual replacement

Controlled process, cancers result from uncontrolled mitosis of abnormal cells

Division of the nucleus (karyokinesis) and the cytoplasm (cytokinesis) are two processes of mitosis

Division of cytoplasm after nucleus. Delayed if cells have more than one nucleus (muscle)

Active process that requires ATP

Prophase

Chromosomes become shorter and thicker by coiling themselves (condensation)

This prevents tangling with other chromosomes

Nuclear envelope disappears/breaks down

Protein fibres (spindle microtubules) form

Centrioles are moving toward opposite poles forming the spindle apparatus of microtubule

Metaphase

Centrioles at opposite poles

Chromosomes line up on the equator of the spindle

Centromeres (kinetochores) attach to spindle fibres

Kinetochores consist of microtubules and "motor" proteins which utilise ATP to pull on the spindle

Anaphase

Spindle fibres pull copies of chromatids to spindle poles to separate them

Mitochondria around spindle provide energy for movement

Telophase

Chromatid at the pole

Sets of chromosomes form new nuclei

Chromosomes become long and thin, uncoil!

Nuclear envelopes form around the nucleus

Cells & Molecules

Cell Division

Cell Types

Cell Ultrastructure

Enzymes

Gene Technology

Genes, DNA, RNA

Large Molecules

Plasma Membrane

Respiration

Content

Cell division

Chromosomes

Meiosis (reduction division)

The Cell Cycle

Interphase

Mitosis

Prophase

Metaphase

Anaphase

Telophase