The Continuity of Life Mrs Tagore

Key words: Histone proteins Centromere Karyotype Homologous Autosome Heterosome Sex chromosomes Haploid Diploid Somatic cell Locus/loci Homologous chromosomes Alleles Plasmid nucleoid

Chromosomes and Eukaryotes Read pages 15-16

Chromosomes and Eukaryotes Read pages 15-16

Chromosomes and Eukaryotes Read pages 17-18

Chromosomes of Prokaryotes Read pages 18-19

Questions Complete questions 1-10 for tomorrow. We will be discussing these in class, so I’ll be checking that you have done it!!

Title: Mitosis Learning question: What are the names of the stages of mitosis? Hook: What connects these pictures? (Can you write more than one word?!)

Lesson Aims Describe the cell cycle Understand that mitosis is only one small part of the overall cell cycle State the events that occur at each phase of the cell cycle Describe each stage of mitosis Identify each stage of mitosis from diagrams and micrographs

Key words… Mitosis Prophase Metaphase Anaphase Telophase Microtubules Cytokinesis Chromatid Chromasome Centromere Centriole Diploid

Cell division All complex organisms originated from a single fertilised egg. Every cell in your body started here, through cell division the numbers are increased. Cells then specialise and change into their various roles

Mitosis Mitosis is the process by which new body cell are produced for: Growth Replacing damaged or old cells. This is a complex process requiring is to be split into different stages to understand it.

DNA ‘Blueprint of life’ Codes for all the proteins needed for life Describes that characteristics of every living thing Every cell with a nucleus contains ALL the instructions to make the organism http://www.pbs.org/wgbh/nova/photo51/media/journey.swf

Chromosomes Each DNA strand is split into chromosomes All sexually reproducing animals have pairs of chromosomes. One set of each pair comes from each parent Humans have 23 pairs Lions have 19 pairs African wild dogs have 39 pairs Mosquito have 3 pairs Some ferns have 500-600 pairs

This (imaginary, example) animal has just two pairs of chromosomes Red = Maternal Blue = Paternal Give out paper chromosomes and an A3 cell outline 1p 1m 2p 2m

1p + copy 1m + copy 2p + copy 2m +copy During Interphase, each chromosome replicates and produces an exact copy of itself: Using cut out chromosomes and paperclips, get students to produce tetrads as above 1p + copy 1m + copy 2p + copy 2m +copy

There are four stages to Mitosis Prophase Metaphase Anaphase Telophase Remember though that this is a continuous process P M A T

Interphase Standard condition of cell DNA replicates Cell enters reproductive cycle with 2 copies of each chromosome

Prophase DNA super coils and chromosomes become visible Nuclear membrane breaks down Centrioles migrate to poles

Metaphase Chromosomes line up centromeres on equator of cell Centrioles form spindles

Anaphase Spindles ‘grip’ centromeres and chromosomes migrate to poles

Telophase Nuclear membranes reform Chromosomes disperse Cytokinesis begins

Interphase Both daughter cells are exact copies of the parent cell

INTERPHASE MITOSIS

Stages of Mitosis http://www.cellsalive.com/mitosis.htm

In humans, each cell (except sex cells) has how many chromosomes After mitosis, how many daughter cells are produced?  _______.  After mitosis (in a human cell), each daughter cell has how many chromosomes? _____ How many phases are in MITOSIS? ___________ Which phase of the cell cycle is the longest?  _________ During which phase does cytokinesis begin?  __________ What cell parts migrate to the poles during prophase? __________________. What structure holds the two chromatids together? ____________________ During which phase does the nuclear membrane dissolve? __________________ What structure moves the chromosomes into position and then pulls them apart? ___________________ What is the overall purpose of mitosis? _________________________

Name the stages!

Binary fission

Binary fission Prokaryotes reproduce by binary fission No nucleus, centromere or chromosomes, therefore no mitosis Two daughter cells produced Cell replication>new DNA attaches itself to different part of cell membrane>cell pulls apart separating replicate and original DNA> wall forms dividing cells into two cells with identical genetic composition Mitochondria and chloroplasts also use binary fission to form new organelles