Cell Reproduction Chapter 8 8 1 Chromosomes Cell

Cell Reproduction Chapter 8

8 -1 Chromosomes Cell Reproduction 8 -2 Cell Division 8 -3 Meiosis

DNA: Chromosomes l Centromere DNA: l l Chromatid l Copy Chromatid l Nucleotides Genes Forms In Eukaryotes: 1. Chromosome Coiled DNA • Histone proteins • Nonhistone proteins • Centromere 1. Chromatin DNA plus protein • Loose storage Chromosome Prokaryotes l Single circular molecule

**Revisiting DNA** Structure Nucleic Acid Nucleotide

Chromosome Structure & Numbers DIPLOID NUMBER

DNA Structure Eukaryotic Prokaryotic Structure of DNA while not replicating chromatin

Types & Organization of Chromosomes l l Sex Chromosomes: l 2 chromosomes l Determines gender l XX= female l XY= male l Carry genes Autosomes: l 44 chromosomes l All other chromosomes Homologous Chromosomes l Pairs carrying genes for same trait Karyotype: l 22 pairs homologous autosomes l 2 sex chromosomes

**Karyotype** What type of organism is this? What sex is this organism? Does this organism have any chromosomal abnormalities?

Cells & Chromosomes l Diploid (2 N) l Both chromosomes in homologous pair l All cells except reproductive cells l Human: l 46 l chrom. = 22 autosome pairs+2 sex chrom Haploid (1 N) l One set of chromosomes from pair l Reproductive Cells: sperm & egg= gametes l Sperm + Egg = zygote (2 N) l Human l 23 chrom= 22 autosomes + 1 sex chrom

# of Chromosomes in Various Organisms ee Diploid Haploid

Karyotype Analysis 1. Identify this organism? 2. Identify the gender? 3. Determine if this is a normal karyotype?

II. **Cell Division: Prokaryotes ** l Binary Fission: l 2 new genetically identical offspring l 3 stages 1. Chromosome copies itself 2. Cell wall forms between chromosomes 3. Cell splits

Cell Division: Eukaryotes l 2 Types: l Mitosis: genetically identical, 2 N l Meiosis: genetically different gametes, 1 N l Cell Cycle l Interphase = prep!!! l G 1 (Gap 1) Phase l S Phase – SYNTHESIS OF DNA l G 2 Phase l Or G 0 Phase: after G 1, exit cell cycle, no division l Mitosis (M phase) l Cytokinesis (C phase)

**Cell Cycle**

**Mitosis Phases** 1. Prophase l Chromosomes form l Nucleolus & nuclear envelope disappear l Centrosomes (contain centrioles) separate to opposite poles of cell l Spindle fibers make mitotic spindle l Kinetochore fibers attach to kinetochore in chromosome l Polar fibers

2. Mitosis Phases Metaphase l 3. Anaphase l 4. Chromatids separate “chromosomes” Telophase l l Chromosomes line up on midline Spindle fibers disappear Chromosomes chromatin Nucleolus and nuclear envelope reforms Cytokinesis: l l l Cytoplasm divides in telophase Cleavage furrow in cell membrane Cell plate: plant cells

**Mitosis** Diagram http: //en. wikipedia. org/wiki/File: Mitosis_drosophila _larva. ogv

**Cytokinesis: Cleavage Furrow & Cell Plate

**Meiosis**: Reproductive Cells Only l l l Forms gametes (1 N) from diploid cells (2 N) l 4 genetically different haploid cells Meiosis I: haploid cells form by end http: //highered. mcgrawl Prophase I hill. com/sites/0072495855/student_vie w 0/chapter 28/animation__how_meiosis l Synapsis tetrad _works. html l **Crossing over** genetic recombination l Metaphase I l Anaphase I l Independent assortment l Telophase I Meiosis II: l Prophase, Metaphase, Anaphase, Telophase II

**Meiosis I**

**Meiosis II (con)**

Spermatogenesis In testes l Produces 4 genetically different haploid spermatids l Spermatids mature into sperm l

Oogenesis In ovaries l Produces l Unequal l 1 Egg Cytoplasm l 3 Polar Bodies Division

Spermatogenesis vs Oogenesis

**Mitosis vs Meiosis**

Asexual & Sexual Reproduction l Asexual l Offspring from 1 parent l Unicellular mitosis or budding l Multicellular budding l Always l genetically identical to parent Sexual l Offspring results from union of gametes= zygote l Offspring genetically different from parents due to meiosis recombining genes l Allows species to adapt more quickly