Mitosis and Meiosis Biology, where multiplication is the same as division

Cell Replication  All new cells come from existing cells  Cells must divide to allow us to grow, repair damaged tissues and reproduce

Chromosomes  Segments of DNA containing many thousand genes  Most mammals have 2 sets of chromosomes that code for the same set of characters  Aka are diploid

Haploid vs. Diploid Haploid  1 set of chromosomes (n)  Sperm/egg  Also male bees, stages of plant and fungal life cycle Diploid  2 set of chromosomes (2n)  Somatic (non- gametic) mammal cells  Stages of plant/fungi life cycle, female bees

Homologous Chromosomes  Contain different versions of the same gene (aka alleles )  One inherited from mother, one inherited from father

Chromosome Terminology

Types of Cell Division Mitosis  Creates identical cells  Growth, repair, asexual reproduction Meiosis  Creates haploid cells with half the chromosomes  Creates gametes (sex cells)

Interphase  DNA is replicated before both mitosis and meiosis in interphase  Cell also grows bigger and makes proteins necessary for new cells

Cytokinesis  Splitting of cell  Occurs after nucleus division (mitosis/meio sis)

Overview Mitosis  One cell division  2 daughter cells  Each contains a single copy of all the chromosomes Meiosis  Two cell divisions  4 daughter cells  Each contain a single copy of half the chromosomes (no homologous chromosomes)

Mitosis

Meiosis

Meiosis I – homologous chromosomes separated

Meiosis II – Replicated Chromosomes Separate

Why does it look like some of the chromosomes have been switched?  They have!  During meiosis, some of the homologous chromosomes are exchanged  Increases genetic diversity

Checkpoints  At certain points the cell cycle is halted until a “go signal” is sent  Aka CDKs  Ensures proper timing of stages, prevents errors and cancers

The Importance of All This  Mitosis creates new identical cells – so every cell in your body is the same  Meiosis creates incredibly unique gametes, increasing genetic diversity  More diversity = more chances of someone surviving

You Are A Unique Snowflake  You randomly get 1 of every one of the 23 chromosomes from your father and from your mother  So there were 2 23 possible combos of sperm and 2 23 possible eggs  So about 8,388,608 possible sperms could have led to you  So there were about 70,368,470,000,000 possible combinations you could have been (not even counting crossing over!)  You really are one in a trillion!

Your Task  In a method of your choosing animate out both mitosis and meiosis  You are not responsible for knowing the stage names, but you do need to know the processes  So make a flipbook, gif, video etc. demonstrating the continuous process of the cell cycles