DNA - Genetic information is stored in the DNA strand in the form of genes. DNA stands for deoxyribose nucleic acid
Genes – located on the DNA strand
2 Types of DNA strands
Chromatin – Normal DNA, found during INTERPHASE (everyday life of the cell)
Thin thread like coils, not visible by microscope
Chromosomes – Packaged DNA, found during MITOSIS (cell division)
Thick condensed super coiled DNA
Chromatid – 1 part of a chromosome
Sister Chromatid –a copy of the original chromatid
Centromere – point where two chromatids attach
Chromosome Number – each species has its own chromosome number parent
Homologous chromosomes – A pair of chromosomes having the same gene sequence, each derived from one
Mom
Dad
Eventually each homologous chromosome will form a sister chromatid before mitosis
Diploid (2N) – two sets of DNA one from each parent
Haploid (N) – one set of DNA
Found in sex cells (egg, sperm)

– the sequence of events that occurs in a cell from mitosis to mitosis
5 events
-3 phases of Interphase, G
1
, S, G
2
-Mitosis
-Cytokinesis (which is really a part of mitosis)
– the everyday life of the cell
Divided into 3 phases
G1 phase – cell growth, cell doubles in size, protein production
S phase – DNA replication (copies itself)
G2 phase – rapid cell growth, prep for cell division
DNA is in the form of Chromatin long thin strands of DNA tangled up in the nucleaus

Late Prophase
– division of the nucleus
Mitosis is the division of the cell nucleus in which the chromosomes in the parent cell divide into two identical sets of cells with the same chromosome number as the parent. Evolutionary Significance is to maintain the chromosome
number. Mitosis occurs in somatic cells (body cells or non sex cells). Cell size causes the cell to divide. When the volume of the cell becomes larger than the surface area, mitosis occurs.
Mitosis occurs in 4 phases – Prophase, Metaphase, Anaphase, Telophase
Early Prophase
Middle Prophase
Chromatin coils and condenses into chromosomes
Nuclear membrane and nucleolus disappears
Centrioles move to opposite ends or poles of the cell
Spindle fibers form across the cell from centriole to centriole and attach to Kinetochore fibers.
Kinetochore fibers extend from the centromere to the centrioles and help control movement of chromosomes
Asters form
Spindle Fibers
Aster s

Kinetochore fibers move the chromosomes to the center of the cell
Chromosomes line up at the center of the cell (cell equator)
Centromere of each pair of chromatids divides
Chromosomes separate
Chromatids move to opposide poles of the cell

Cytokinesis (division of the cytoplasm) occurs
Identical sets of chromatids at opposite poles
Centrioles and spindle fibers disappear
Chromatids unwind and elongate back into chromatin
Nuclear membrane and nucleolus reform
Cell Plate Cleavage Furrow
division of the cytoplasm, this is really a part of Telophase
In animal cells – cell pinches inward forming a cleavage furrow to form two new daughter cells
In plant cells – cell forms a cell plate which develops into a cell wall separating the two daughter cells
MITOSIS RESULTS – 2 DIPLOID IDENTICLE DAUGHTER CELLS

– reduction division, produces gametes (sex cells, egg and sperm)
Meiosis I
Meiosis II
Process of reduction division that produces gametes in which the number of chromosomes per cell is cut in half
(haploid) through the separation of homologous chromosomes.
Homologous Chromosomes – chromosomes that have a corresponding chromosome from the opposite sex parent.
Diploid – (2N) A cell that contains both sets of homologous chromosomes is diploid, which means “two sets”
Haploid – (N) A cell that contains only one set of chromosomes is haploid.

-3 phases of Interphase, G
1
, S, G
2
-Meiosis I and Meiosis II
-Cytokinesis
– Just like interphase before mitosis
G1 phase – cell growth, cell doubles in size, protein production
S phase – DNA replication (copies itself)
G2 phase – rapid cell growth, prep for cell division
PROPHASE I
Chromatin coils into chromatids and the homologous pairs of each come together to form a tetrad
Tetrad - A four-part structure that forms during prophase I of meiosis I and consists of two homologous chromosomes, each composed of two sister chromatids.
Crossing over - The exchange of genetic material between two paired chromosomes (Tetrad).
Crossing over is important because it is a way to recombine the genetic material so that each person (except for identical twins) is genetically unique.
METAPHASE I
Tetrads line up at the equator of the cell
ANAPHASE I
Homologous Chromosomes separate and are pulled to the poles of the cell (the centromeres do NOT split)
TELOPHASE I
Chromosomes uncoil, spindle breaks down, the nuclear membrane and nucleoli reform
Cytokinesis occurs ( division of the Cytoplasm) to form two cell
NOTE: THERE IS NO INTERPHASE BETWEEN MEIOSIS 1 AND MEIOSIS II
just like Mitosis except that there is only half the number of chromosomes
PROPHASE II - METAPHASE II - ANAPHASE II - TELOPHASE II - CYTOKINESIS
MEIOSIS RESULTS – 4 HALPLOID (N) GAMETES

MEIOSIS RESULTS – 4 HALPLOID (N) GAMETES MITOSIS RESULTS – 2 DIPLOID
IDENTICLE DAUGHTER CELLS

11. What moves the chromatids during mitosis? _________________________________________
12. What anchors the spindle? ___________________________________________
13. What are the four phases of mitosis? ________________________________________________________________
14. How many daughter cells are created from mitosis and cytokinesis? _________________________________
15. During what phase does cytokinesis begin? ____________________________________________
16. If a human cell has 46 chromosomes, how many chromosomes will be in each daughter cell? ___________
17. If a dog cell has 72 chromosomes, how many daughter cells will be created during a single cell cycle?__________
Each of these daughter cells will have how many chromosomes? _____________
18. The nuclear membrane dissolves during what phase of cell division? ____________________________________
19. In the cell pictured above how many chromosomes are present during prophase? ________________________
20. What structure holds the individual chromatids together? _______________________________________

5.
6.
7.
8.
Name of Phase
1.
2.
3.
4.
Description
Homologous chromosomes pair up and form tetrad
Spindle fibers move homologous chromosomes to opposite sides
Nuclear membrane reforms, cytoplasm divides, 4 daughter cells formed
Chromosomes line up along equator, not in homologous pairs
Crossing-over occurs
Chromatids separate
Homologs line up alone equator
Cytoplasm divides, 2 daughter cells are formed

1. _________________ is a kind of cell division that produces haploid cells with ½ the number of chromosomes of the parent cell. a. mitosis b. meiosis
2. Cells undergo meiosis to _____________________ a. grow bigger b. repair injuries c. replace worn out cells d. make gametes
3. A group of 4 chromatids that forms during synapsis is called a _________________ a. biad b. triad c. tetrad d. quadrad
4. The exchange of genetic material between arms of homologous chromosomes is called ________________________ a. synapsis b. independent assortment c. asexual reproduction d. crossing over
5. During meiosis, crossing over happens in ______________________ a. prophase I b. metaphase I c. prophase II d. interphase II
6. During meiosis a 2n parent cell divides to produce __________________________ a. four identical 2n cells b. two identical 2n cells c. two identical 1n cells d. four different 1n cells
7. DNA located in the cell during Interphase is in the form of ____________________________ a. Chromatin b. Chromosomes
8. Division of the cytoplasm is called _______________________________ a. mitosis b. cytokinesis c. replication d. diploid
9. Reduction division is used to describe what type of cell division? a. mitosis b. meiosis
What is the end result of Mitosis? ____________________________________________________________________________
What is the end result of Meiosis? ____________________________________________________________________________