QOD How many chromosomes do you have? Identify them. How many from your father? Mother?

Chapter 8: Cell Reproduction Section 8-1: Chromosomes

To return to the chapter summary click escape or close this document. Chromosome Structure

Chromosome Structure  Chromosomes = DNA + Proteins  Levels of organization: –DNA –Nucleosome = DNA + Histones –Coils –Supercoils –Chromosome

Chapter 8 Chromosome Structure Section 1 Chromosomes

To return to the chapter summary click escape or close this document. Chromosome

Chromosomes  Before Cell Division –Chromatin –Thinned out  During Cell Division –Thickened –Chromosomes  Chromatids (2)  Centromere

Chromosome Types and Numbers  Types: –Sex chromosomes –Autosomes –Homologous chromosomes –Karyotype  Numbers: –Diploid (2n) –Haploid (n)

Karyotype

Karyotype

QOD How many chromosomes does a skin cells have after it divides by mitosis? What happens to ensure this number is achieved? When?

Chapter 8: Cell Reproduction Section 8-2: Cell Division

Cell Division  In Prokaryotes –Binary fission  In Eukaryotes –Mitosis –Meoisis

Section 2 Cell Division Chapter 8 Cell Division in Prokaryotes

QOD Define mitosis. What is the end result of mitosis?

To return to the chapter summary click escape or close this document. Stages of Cell Cycle

III. The Cell Cycle  Interphase –G1 –S–S–S–S –G2  M Phase –Mitosis –Cytokinesis

The M phase  Mitosis – Division of the nucleus –Prophase –Metaphase –Anaphase –Telophase  Cytokinesis – Division of the cytoplasm

Mitosis

To return to the chapter summary click escape or close this document. Animal cell undergoing mitosis

Prophase  Nucleus disappears  Centrosomes/Centrioles move  Spindle fibers form – mitotic spindle –Kinetochore fibers/ Kinetochore –Polar fibers

Mitosis continues  Metaphase –Metaphase plate  Anaphase –Role of kinetochore  Telophase –Reversal of prophase –Results:

QOD How does the cell control the cell cycle? What happens when control is lost?

To return to the chapter summary click escape or close this document. Animal cell undergoing mitosis

To return to the chapter summary click escape or close this document. Plant Cell Undergoing Mitosis

Cytokinesis  Division of the cytoplasm  Separates two nuclei into two distinct daughter cells  Animal cells – cleavage  Plant cells – form cell plate

Control of Cell Division  Checkpoints: –G1 –G2 –Mitosis  Loss of control –Cancer

QOD Compare and contrast mitosis to meiosis

Chapter 8: Cell Reproduction Section 8-3: Meiosis

To return to the chapter summary click escape or close this document. Homologous Chromosome

Meiosis  “Reduction” division  Produces gametes  2 divisions  Diploid  haploid  Fertilaztion – n + n = 2n

To return to the chapter summary click escape or close this document. Meiosis Diagram

Meiosis I  Prophase I –Much of it same as prophase in mitosis  Nucleus/nucleolus disappears  Chromosomes coil  Centrioles and spindle fibers –Homologous chromosomes pair up  Synapsis  Forms a tetrad  Crossing-over  genetic recombination

To return to the chapter summary click escape or close this document. Crossing Over Diagram

QOD What is independent assortment?

Meiosis I  Metaphase I –Tetrads line up  Anaphase I –Independent assortment  genetic variation  Telophase I –Cytokinesis begins –Forms 2 haploid cells

LE 13-8ab Sister chromatids Chiasmata Spindle Centromere (with kinetochore) Metaphase plate Homologous chromosomes separate Sister chromatids remain attached Microtubule attached to kinetochore Tetrad MEIOSIS I: Separates homologous chromosomes PROPHASE I METAPHASE I ANAPHASE I Homologous chromosomes (red and blue) pair and exchange segments; 2n = 6 in this example Pairs of homologous chromosomes split up Tetrads line up

Meiosis II  No copying of DNA  Follows process of mitosis  Prophase II  Metaphase II  Anaphase II  Telophase II  Cytokinesis

LE 13-8b Cleavage furrow MEIOSIS II: Separates sister chromatids PROPHASE II METAPHASE IIANAPHASE II TELOPHASE I AND CYTOKINESIS TELOPHASE II AND CYTOKINESIS Sister chromatids separate Haploid daughter cells forming Two haploid cells form; chromosomes are still double During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes

Results  Gametes –4 haploid cells –Genetically different  Males: –Spermatogensis  Females: –Oogenesis –1 egg cell, 3 polar bodies

Chapter 8 Meiosis in Male and Female Animals Section 3 Meiosis