Biology, where multiplication is the same as division 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 1 set of chromosomes (n) Sperm/egg Also male bees, stages of plant and fungal life cycle 2 set of chromosomes (2n) Every cell but the gametes 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

Mitosis Meiosis Types of Cell Division Creates identical cells Growth, repair, asexual reproduction 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)

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

Mitotic Cycle

Checkpoints At certain points the cell cycle is halted until a “go signal” is sent Cyclin must bind to Cyclin Dependent Kinases Ensures proper timing of stages, prevents errors and cancers

Mitosis

Meiosis

Meiosis I – homologous chromosomes separated

2 Major Events Segregation of Homologous Chromosomes Independent Assortment One homolog ends up in each gamete, leaving the cell with 23 unpaired chromosomes Which homolog is inherited for each pair is entirely random

Meiosis II – Sister Chromatids 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

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 223 possible combos of sperm and 223 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 (1-3 people) Focus less on the stage names than on what is occurring over the process So make a flipbook, gif, video etc. demonstrating the continuous process of the cell cycles Your initial cell should contain 3 pairs of homologous chromosomes (6 total) Label them 1A, 1B, 2A, 2B, 3A and 3B. Color code them