1. Mitosis and Meiosis Notes

2. Important info, before we begin…
Chromosome: a rod-shaped structure, usually found in pairs in a cell nucleus that carries genes that determine the characteristics of an organism.
Tons of DNA is all coiled up inside each of these chromosomes
A human body cell usually contains 46 chromosomes (23 pairs)

3. Organisms can reproduce sexually or asexually
Asexual Reproduction
Single parent passes all genes to offspring
Identical “clones” of parent
Entire population of species is identical
Common in unicellular organisms

4. PROKARYOTIC CELLS DIVIDE ASEXUALLY
These are unicellular organisms (bacteria normally)
Their cells possess a single chromosome, containing genes
The chromosome is replicated
The cell then divides into two cells, a process called binary fission
Prokaryotic chromosomes
Figure 8.3B

5. Division into two cells
Binary fission of a prokaryotic cell
Prokaryotic chromosome
Duplication of chromosome and separation of copies
Continued growth of the cell and movement of copies
Division into two cells
Figure 8.3A

6. Sexual Reproduction
Unique combination of 2 parents genes; each contributing half the offspring’s DNA
Combination of parental genes and traits
Wide variation in physical and behavioral traits
Common in multicellular organisms

7. A little bit of review…
What is a prokaryotic cell?

8. A little bit more review…
True or False: You are made up of Eukaryotic cells.

9. WORK IT…
Sexual vs. Asexual Worksheet

10. THE EUKARYOTIC CELL CYCLE AND MITOSIS
A eukaryotic cell has many more genes
than a prokaryotic cell
The genes are grouped into multiple chromosomes, found in the nucleus
Chromosomes contain a very long DNA molecule with thousands of genes
Individual chromosomes are only visible during cell division
Before a cell starts dividing, the chromosomes are duplicated
This process produces sister chromatids

11. Chromosome distribution to daughter cells
Chromosome duplication
Sister chromatids
Chromosome distribution to daughter cells

12. Mitosis

13. Why do we need more cells?
What IS Mitosis?
A way for the cell to make an EXACT copy of itself.
Each daughter cell has EXACTLY the same DNA as the original cell.
Why do we need more cells?
To REPLACE old, worn out cells
To REPAIR injuries
To REPRODUCE (for some unicellular organisms)
Cell division serves an important role in an organism's HEALTH and GROWTH. In an adult human, millions of cells divide each second to maintain homeostasis.
Homeostasis = the organism and all its parts are stable and working properly so that the organism is healthy

14. MITOSIS Mitosis consists of 5 major phases: Interphase Prophase
Metaphase
Anaphase
Telophase/Cytokinesis
Figure 8.5

15. INTERPHASE DNA exists as chromatin. Growth and DNA replication occur
centrioles
DNA exists as chromatin.
Growth and DNA replication occur
90% of a cell’s life cycle is in this stage
Chromatin
Nuclear envelope

16. PROPHASE Chromatin condenses to chromosomes. Spindle fibers form.
Centriole
Chromosome
Chromatin condenses to chromosomes.
Spindle fibers form.
Nuclear envelope breaks up and the centrioles align at the poles.
Spindles
Centriole

17. (in middle of chromosome)
Centriole
METAPHASE
Spindles
Metaphase plate
Chromosomes line up single file in the middle of the cell, perpendicular to the centrioles.
Spindle fibers are attached to the centromeres.
Centriole
Centromere
(in middle of chromosome)

18. ANAPHASE
Spindle fibers retract, ripping the chromosomes in half at the centromere.
Identical (daughter) chromosomes are pulled to the poles of each side of the cell.
Centromere
Centrioles
Daughter chromosomes
Spindle Fibers

19. TELOPHASE AND CYTOKINESIS
Centriole
Chromatin
Chromosomes become chromatin.
Nuclear envelope reforms, cleavage furrow develops in animal cells and the cell eventually splits.
Cleavage furrow
Chromatin
Centriole

20. CYTOKINESIS Cytokinesis….This process pinches the cell apart
Cleavage furrow
Cleavage furrow
Contracting ring of microfilaments
Daughter cells

21. WORK IT… Virtual Mitosis Lab (access on class website)
Amoeba Sisters Video on the basics of Mitosis (access on class website)
Mitosis Drawing Worksheet
Mitosis Mini Review

22. Meiosis

23. A Review of Sexual Reproduction:
Unique combination of 2 parents genes; each contributing half the offspring’s DNA
Combination of parental genes and traits
Wide variation in physical and behavioral traits
Common in multicellular organisms

24. You are a combination of two gametes (or sex cells)
Cells with two sets of chromosomes (like your body cells) are said to be diploid (46 chromosomes) Gametes are haploid, with only one set of chromosomes (human sperm or egg cells = 23 chromosomes)
At fertilization, a sperm fuses with an egg, forming a diploid zygote which will give the resulting baby 46 chromosomes….
23 from each parent

25. So, what is MEIOSIS?...The creation of sperm and eggs

26. 10 Stages…… (If you include Interphase)
MEIOSIS
10 Stages…… (If you include Interphase)

27. MEIOSIS I: Homologous chromosomes separate
Interphase
MEIOSIS I: Homologous chromosomes separate
METAPHASE I
ANAPHASE I
Interphase
Centrioles)
Growth and DNA replication occurs.
DNA exists as chromatin.
Most of a cell’s life cycle is in this stage.
Nuclear envelope
Chromatin

28. Prophase I Chromatin coils up into chromosomes.
Chromosomes, composed of sister chromatids, come together as pairs.
The nuclear envelope breaks up.
Spindle fibers form.
“Crossing over” may occur between the chromosomes (see circles on diagram)
Crossing over is when chromosomes come together and sections of the chromosomes are exchanged. This provides greater genetic variation.
Spindle Fibers
Centrioles
Chromosomes

29. Metaphase I
Centrioles
The chromosome pairs line up in the middle between the poles.
Spindle fibers are attached at the centromere.
Spindle Fibers
Chromosomes

30. Anaphase I Chromosome pairs are separated
Spindle fibers grab chromosomes at the centromeres and pull them apart towards opposite poles and centrioles.
Chromosomes
Spindle Fibers
Centromere
Centrioles

31. Telophase I Cleavage furrow develops
Nuclear envelope begins to reform.
Double chromosomes start to uncoil.
Eventually, the cell splits into two.
Chromosomes
Cleavage
Centrioles

32. Now Meiosis II begins…. ***Make sure to draw arrows and label parts on each slide

33. Prophase II Spindle fibers form Nuclear envelope breaks up.
Chromatin coils up into double chromosomes (composed of sister chromatids).

34. Metaphase II
Double chromosomes line up single file in the middle of the cell.
Spindle fibers are attached at the centromere.

35. Anaphase II
Spindle fibers retract, ripping the double chromosomes in half at the centromere
Single chromosomes are pulled apart towards the poles of each side of the cell

36. Telophase II Nuclear envelope reforms
Chromosomes uncoil into chromatin
Cleavage furrow develops in both cells and eventually splits into 4 sex cells (gametes), each with the haploid number of chromosomes.

37. MEIOSIS is different in BOYS and GIRLS
OOGENESIS
SPERMATOGENESIS
*Made in the ovaries—Produces 4 cells but only 1 survives as an egg
*Made in the testes—Produces 4 sperm

38. Work it…
Haploid/Diploid Practice
Meiosis Cartoon Project
Meiosis Mini-Review

39. Let’s review some Similarities and Differences between Mitosis and Meiosis