Mitosis Round up Purple booklet Microscope images

Cell cycles and Life cycles Why is mitosis important? Starter: Why do cells have to undergo mitosis?

Success criteria Explain the significance of mitosis for growth, repair and asexual reproduction in plants and animals. Define the term Stem Cell Outline with the use of photographs and diagrams the process of cell division in yeast.

Cellular reproduction Mitosis and cytokinesis Binary fission – production of prokaryotes. Cloning – Asexual reproduction Artificial cloning - cloning Dolly, plant cuttings.

Binary Fission https://www.tes.co.uk/teaching-resource/Binary-Fission-Prokaryotic-Cell-Division-6355626/

Budding (Yeast) 1 A bud is formed at the surface of the cell 2 Interphase – DNA and organelles replicated 3 Set of duplicated chromosomes – each set contained within a nucleus 4 One daughter nucleus migrates into the bud 5 Bud increases in size and eventually separates from parent cell – producing a new, genetically identical yeast cell. This is called “Budding”

Yeast Budding

Different organisms, different cell cycles Animals Plants Most cells in an animal can undergo mitosis and cytokinesis. Important for repairing damaged tissues. Cytokinesis : occurs from the outside in causing a cleavage. Only the root and shoot tips and a ring of tissue in the stem, are able to divide and grow. Cytokinesis starts with a cell plate forming where the spindle equator was. Here new cell wall material is laid down.

Stem Cells Multicellular organisms function as a result of many different cell types that are specialised for their function – e.g: Red blood cells (erythrocytes) – specialised for the carriage of oxygen around the body Vascular tissue (xylem and phloem) in plants - cells in the cambium tissue of plants differentiate to form vascular tissue – specialised for transport All cells in multicellular organisms originate from stem cells. These are unspecialised cells that divide to become new cells, which then differentiate to become specialised into different cell types. Differentiation is achieved due to the switching on and off of relevant genes.

Key words Pluripotent – can differentiate into some cells Totipotent - can differentiate into ANY cell

Embryonic vs Adult stem cells Embryonic stem cells are totipotent and can turn into any type of cell Adult stem cells are pluripotent- they can turn into some cells. E,g, in the bone marrow, stem cells can turn into bone and blood cells.

Meiosis Key points Meiosis produces haploid cells. Homologous chromosomes divide into the 4 cells independently of each other.

Meiosis Diploid animal cells produce haploid sex cells, the egg/sperm cell. Meiosis differs to mitosis by producing cells which have half the number of chromosomes. Producing cells that are genetically different to each other.

Practise questions Describe the roles of stem cells in animals and plants. (5) Describe the difference between asexual and sexual reproduction using a range of organisms as examples. (8)

Task – complete the questions