Ch. 12: mitosis, Meiosis, and life cycles

How does a plant grow? Cell cycle – Activities of a cell from one cell division to the next

What is a chromosome? =

Cabbage: 18 Cotton: 52 Mango: 40 Corn: 20 Foxglove: 56 Oak tree:24

Fig 8.7

The Events of the Interphase Interphase: – Divided into 3 phases: G1 – S – G2 – cell growth after DNA replication; cell prepares to divide

Cell Division or “M” phase Cell Division consists of two parts 1. Mitosis: 2. Cytokinesis: What needs to happen to the chromosomes prior to Mitosis? During mitosis?

Fig 8.6

Each chromatid has one DNA molecule Centromere Sister chromatids 1. How do sister chromatids compare genetically? 2. What happens to sister chromatids during mitosis? Sketch of one duplicated chromosome

Mitosis: sister chromatids separate Two-chromatid chromosome Interphase S-Phase: DNA Replication One-chromatid chromosome One-chromatid chromosome The number of chromosomes in each daughter cell is the same as the number of chromosomes in the parent cell

Mitosis: Division of the Nucleus Four Stages: 1.Prophase – Chromosomes attach to spindle fibers 2.Metaphase – Spindle fibers align the chromosomes at the equator of the cell 3.Anaphase – 4.Telophase – nuclear envelope forms around each cluster of chromosomes

Fig 8.8

Cytokinesis: division of the cytoplasm to create 2 new cells

Fig 8.9

Mitosis Meiosis – A reductive division (46 C  23 C) – Daughter cells are genetically different

Normal Karyotype of Human Chromosomes Karyotype = How many pairs of chromosomes in this Karyotype? Paired chromosomes are homologous =

Diploid cell: 3 sets of homologous chromosomes One set of non-homologous chromosomes Haploid cell One set of non- homologous chromosomes Haploid cell

Diploid cell – Haploid cell – contains only ONE chromosome of each pair (n)

Meiosis Only occurs within the male and female sporangium (all other cell divisions are mitosis)

Fig 8.15

Fig 8.16 Meiosis I

Stages of Meoisis 1.Interphase – same as mitosis (G1, S, G2) 2.Meiosis I a)Prophase I – b)Metaphase I – c)Anaphase I – d)Telophase I – 3.Meiosis II a)Prophase II – chromosomes attach to spindle b)Metaphase II – chromosomes align at equator c)Anaphase II – sister chromatids separate d)Telophase II – cells divide, end result = 4 haploid daughter cells

Plant sexual life cycles: Alternation of Generations

2 multicellular life stages: 1.Sporophyte: Spores – haploid cells that can grow into a new, multicellular, haploid organism (the gametophyte) without fusing to another cell. 2.Gametophyte: Egg & sperm fuse to form the diploid zygote, which divides by mitosis to form the sporophyte