Cell Reproduction Chapters 9 & 11

Types of Reproduction Mitosis Asexual – only 1 parent needed & the offspring are identical to the parent cell. Meiosis Sexual – cells from 2 parents fuse to form new individual. These cells must have ½ the DNA of the parent cells.

Cell Cycle G1 – growth phase, most of life span S – DNA synthesis ( 2-4 hrs) G2 – short growth period (4-8 hrs) M – mitosis or meiosis begins G0 – cells that do not divide

Cell Cycle Events of the Cell Cycle

Mitosis Mitosis is division of the nucleus Cytokinesis is division of the cytoplasm Nuclear material is DNA Chromatin – diffuse DNA, spread out Chromosomes – coiled DNA, compact Eukaryotes have pairs of chromosomes

Figure 9.7 figure jpg

Phases of Mitosis Interphase Non-dividing stage. G1, S, G2 Cell carries on normal functions. DNA and centrioles are replicated in preparation for cell division.

Prophase Chromosomes coil and become compact. Chromosomes appear double stranded. Chromatids attached at the centromere. Centrioles move to the poles. Asters form around centrioles. Spindle fibers extend across the cell. Nuclear membrane and nucleolus disappear.

Figure 9.9 figure jpg

Metaphase Double stranded chromosomes individually line up on the equator Centromeres attach to a spindle fiber CENTROMERE CHROMATID CENTRIOLE

Anaphase Chromosomes split & separate and are pulled to opposite poles of the cell by the spindle fibers

Telophase Cytoplasm divides (cytokinesis) New nuclear membranes form Plant cells build a new cell wall. Animal cells pinch in and separate.

Terminology MitosisMeiosis Asexual TypeSexual Diploid Chromo.#Haploid 2n n Zygotes Cell typesGametes

Meiosis There are 2 cell divisions in meiosis. Interphase I Chromosomes & centrioles replicate

Prophase I Chromosomes coil and become double stranded. Centrioles move to the poles. Asters and spindles form. Nucleolus and nuclear membrane disappear. Homologous chromosomes synapse. Crossing over occurs. This results in the creation of variations in the chromosomes

Metaphase I Chromosomes line up in pairs on the equator. Crossing over continues.

Anaphase I Homologous chromosomes separate and move to opposite poles. Each new cell will receive 1 copy of the original chromosome pairs.

Telophase I Cytokinesis occurs. Each cell has half the number of chromosomes as the original parent cell. Chromosomes are still double stranded.

Interphase II Chromosomes are uncoiled, but still double stranded. NO DNA replication occurs. Centrioles are replicated. Cells contain half the chromosome number as the parent cell.

Prophase II Same as Mitosis Metaphase II Same as Mitosis Anaphase II Same as Mitosis Telophase II Same as Mitosis

Results of Meiosis 1 parent cell produces 4 daughter cells Daughter cells are haploid gametes. Fertilization results form the fusion of 2 haploid gametes to form a diploid zygote.

Spermatogenesis Sperm cell formation 4 equal sized gametes form 46D 46 23D 23

Oogenesis Egg cell formation 1 large egg + 3 polar bodies (die) 4646D 23D 23

Mitosis vs. Meiosis D 23 Meiosis Mitosis Diploid Cells Fertilization Haploid Cells Gametes Zygote

Genetic Variations Sexual reproduction (fertilization) Meiosis - independent assortment Meiosis - crossing over Random Mutations