Mitosis/Meiosis Asexual/Sexual Reproduction

Cell Growth Types of Reproduction- –Asexual Reproduction- One parent produces an offspring and it is identical to the parent. Ex: Ameba/Paramecium Sexual Reproduction- Two parents are necessary to produce an offspring and the offspring is not identical to the parent. Ex: Humans

REPRODUCTION IS NOT NEEDED FOR THE SURVIVAL OF AN INDIVIDUAL BUT IS FOR THE SPECIES.

The Cell Cycle 1. A period of growth and development 2. The following occurs in the cell cycle –a) the cell grows –b) the cell prepares for division –c) the cell divides into two –d) the cycle begins again

Stages of Growth Interphase- –Includes the G1, S and G2 phase. –G1 Phase- Period of growth when cells increase in number NOT IN SIZE –S Phase- Chromosomes replicate and DNA is formed and replicated –G2 Phase- Shortest of the three when organelles are developed.

M PHASE M Phase- AKA Mitosis phase –When the cell actually divides –Mitosis- A process that produces two identical daughter cells. There are five stages of mitosis Asexual Reproducing organisms and cells use the PROCESS OF MITOSIS

Phase of Mitosis Interphase- Includes G1, S, G2 it preps the cell for division. A) Prophase B) Metaphase C) Anaphase D) Telophase E) Cytokinesis

PROPHASE Chromosomes become long and thick Centrioles move to opposite ends of cell Nuclear membrane disappears Spindle fibers appear

Metaphase Chromosomes line up down the middle of the cell

Anaphase Centromere divides and creates chromatids They move to opposite ends of the cell

Telophase Final stage 2 identical sets of chromosomes Nuclear membrane reappears

Cytokinesis Occurs immediately after telophase Cytoplasm divides The cell cycle begins again

Regulating the Cell Cycle Cyclins- are proteins that regulate the timing of the cell –2 Types: Internal- control activity inside the cell External- control activity outside the cell

CANCER Cancer is defined as uncontrolled cell division. Cancer cells do not respond to regulators As a result they form masses of cells called tumors –Tumors are malignant or benign

MEIOSIS Meiosis- is the process of making sex cells/gametes (sperm and egg). It is also called “reduction division” because the process reduces the chromosome number from 46-23

Meiosis allows the chromosome number to go from the DIPLOID to the HAPLOID The Diploid number- is the total chromosome number 2(n) The Haploid number- is half of the diploid (n) –Another name for haploid is monoploid –Gametes have the haploid number –Ex: Humans have 23 (haploid) pairs of chromosomes 2(23)= 46 (diploid)

Meiosis I There are two meiotic divisions. –Meiosis I includes: Interphase I,Prophase I Metaphase I Anaphase I Telophase I Interphase I and Prophase I are the most important in Meiosis

Interphase I and Prophase I Interphase I- DNA replicates to form duplicate chromosomes. Prophase I (most important) is when homologous (same) chromosomes pair to form a tetrad.

These are homologous chromosomes forming a tetrad Because they get so close they cross over CROSSING OVER PROVIDES FOR MORE GENETIC VARIATION Crossing over takes place in PROPHASE I

The remaining phases –Metaphase I, Anaphase I, and Telophase I are very similar to mitosis. –At the end of Telophase I you have two cells not identical to the parent

MEIOSIS II In Meiosis II the two unidentical cells that were formed from Meiosis I go through each stage again except for interphase. By the end there are 4 unidentical cells with half the chromosome number

Sex Cells/Gametes The process of meiosis is to create sex cells (sperm and egg) Gametes are made during gametogenesis. FemaleMale GameteEgg/Ovum Sperm GonadOvary Testes

Sperm Cells- 4 cells result from Meiosis and they each carry the haploid/monoploid number of chromosomes (23) Egg Cells/Ovum- 4 eggs result from Meiosis, however only 1 is functioning the others are called polar bodies. This ovum also has the haploid number (23) Fertlization- process when a sperm fuses with an egg to form a zygote. The diploid number is restored = 46

MitosisMeiosis 1 division2 divisions Makes 2 identical Makes 4 cells unidentical cells Creates all cells inCreates gametes the body