1. Chromosomes and Mitosis/Meiosis

2. Info. On Chromosomes Vocabulary DNA existing as thin, uncoiled strands
1. Chromatin: DNA and Protein
DNA existing as thin, uncoiled strands
This looks like spaghetti in the nucleus.
2. Chromosome: A visible carrier of the genetic information.
Chromosomes contain many genes. Every human cell contains
23 pairs of chromosomes Females: XX Males: XY
3. Chromatids: are identical copies of a chromosome.
sister chromatids contain the same genes and same alleles.
4. Centromere: Point at which the pair of chromatids are
attached.
5. Allele: alternative forms of a gene

3. Autosomes/somatic: body cells; chromosome pairs 1-22
Sex Chromosomes: 23rd pair- determines sex of child
Human
Karyotype
Homologous chromosomes: Each pair is similar in size,
shape, and genetic content.

4. Cell Cycle Steps in the cell cycle 1. Interphase: G1, S, G2
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase
6. Cytokinesis
These are the steps in the entire cell cycle.
Each new cell has 46 chromosomes.
Cells are identical to each other: Called daughter cells
Mitosis

5. Mitosis if Animal cells

6. Mitosis in Plant Cells

10. Interphase Period of cell growth Not a true stage of mitosis
Can’t see chromosomes at first – duplication
90% of time
G1: Normal Growth Phase
S: DNA Duplicates and Pairs together
G2: all other cell structures duplicate

11. Prophase Chromosomes become visible Nuclear membrane dissolves
In animal cells, 2 centrioles move to opposite ends of cell
Spindle fibers between centrioles stretch across the call

12. Metaphase Double stranded chromosomes line up around center of cell
Each centromere becomes attached to a spindle fiber
Spindle fibers link the chromatids of each chromosome to opposite poles

13. Anaphase Each centromere divides
Two chromatids (now called chromosomes) move toward opposite poles as spindle fibers attached to them shorten

14. Telophase Centrioles and spindle fibers start to disappear
Chromosomes uncoil/stretch out and become hard to see
Nuclear membrane forms around each mass of chromosomes – forms new nuclei
Cytokinesis begins - cytoplasm separates into 2 new cells

15. Cytokinesis: The division of the cytoplasm after Mitosis (division of the nucleus) occurs. Final step in cell cycle.

16. Animal Cell – Cytoplasm pinches apart
Plant Cell – CELL PLATE forms between cells – before cell walls form

18. Checkpoints G1 checkpoint: decides of cell will divide
a. S phase- Interphase (where DNA
is copied). When its not the right conditions, cells
will exit S phase and stay in resting period
forever. Cells such as brain and some nerve cells
stay in resting period and never divide.
2. DNA synthesis (G ) checkpoint: Replicated DNA is checked
for errors.
Mitosis checkpoint: Triggers exit from mitosis. Signals G1
phase.

19. Cancer 1. Uncontrolled growth of cells.
Genes contain info needed to make the proteins that
regulate cell growth and division. Mutations of these genes
can cause the proteins to malfunction and normal cell growth
and regulation is disrupted.
Mutations cause overproducing growth-promoting molecules, speeding
up the cell cycle. (stepping on the accelerator)
Inactivating the proteins that slow or stop the cell cycle (taking away the
brakes)
Benign: tumors in which cancer cells remained in original site, can be
removed successfully with out individuals having cancer. Inability to
Metastasize (spread). Most are not harmful. Can be removed
Malignant: Cancerous tumors. They will Metastasize causing
cancer. Treated with Radiation and Chemotherapy.

21. MEIOSIS! (p142) (diploid Cells= 46)
Two Parts: Meiosis I and Meiosis II
Meiosis I
1. Prophase 1: Nucl. Mem. Goes away, Nucleolus goes away,
centrioles form spindles, Forms XX Tetrad ,
crossing over occurs___________
2. Metaphase 1: Chromosome PAIRS line up in the
middle
3. Anaphase 1: Chromosome pairs go towards
centrioles at opposite ends of the cell.
4. Telophase1: Chromosomes are at opposite ends
and the cytoplasm divides. (nucleolus comes back,
nucleus comes back etc…
5. cytokinesis1. Cytoplasm splits into
2 genetically different cells.
(diploid Cells= 46)

22. CROSSING OVER
When portions of a chromatid (one of a pair of strands of DNA) on one homologous chromosome are broken & exchanged with the
corresponding portions on one of the chromatids of the other homologous chromosome.

23. a. Prophase 2: nucl. Mem/Nucleolus goes away, spindles form
MEIOSIS II
a. Prophase 2: nucl. Mem/Nucleolus goes away, spindles
form
b. Metaphase 2: Chromosomes line up in the middle
c. Anaphase 2. Chromosomes split at centromere
Move to centrioles
d. Telophase 2: nucleolus/ nuc. Mem.
Comes back, spindles go
away, cell starts to split
e. Cytokinesis 2: cytoplasm splits
into 4 genetically
different cells.
(Haploid= 23)
3:34

26. MEIOSIS CONTRIBUTES TO GENETIC VARIATION
3 Mechanisms make key contributions to genetic variation in Meiosis:
1. INDEPENDENT ASSORTMENT:
- Random distribution of homologous chromosomes during Meiosis
- 8 million different gene combinations!
2. CROSSING OVER
RANDOM FERTILIZATION:
- 70 trillion possible outcomes!

27. Independent Assortment

28. GAMETE FORMATION IN MALE/FEMALE ANIMALS (p146)
SPERMATOGENESIS
- Process by which sperm are produced in male animals
- Occurs in Testes
- Resulting 4 Haploid cells = SPERM

29. OOGENESIS
- Process by which gametes are produced in female animals
- Occurs in Ovaries
- Resulting in larger egg or OVUM with most of the cytoplasm to nourish developing organism.

33. CLONE Produced by Asexual Reproduction
– Genetically identical to its parents!

34. Parthenogenesis! (Ex: Drones – Bees)
New individual develops from an unfertilized egg
(Ex: Drones – Bees)
a form of reproduction in which the ovum develops into a new individual without fertilization. Natural parthenogenesis has been observed in many lower animals. In many social insects, such as the honeybee and the ant, the unfertilized eggs give rise to the male drones and the fertilized eggs to the female workers and queens.
It has also been observed in some snakes, fish,
and monitor lizards.