1. Cell Growth and Reproduction
Cell Size
Mitosis
Meiosis

2. Growth in Organisms
For an organism to grow, its cells divide instead of getting larger.

3. Cell Size Limitations 1
Large cells would have to wait too long to diffuse nutrients in and waste out.
Ex. a/c

4. Cell Size Limitations 2
One set of DNA can’t make enough proteins and enzymes fast enough for a large cell.
Ex. Only one cook

5. Cell Size Limitations 3 Surface area-to-volume ratio:
The volume (inside) of the cell increases a lot faster than the surface area (membrane).
Ex. Solar panels
1mm
2mm
4mm
Surface area =6mm Surface area= 24mm Surface area= 96mm2
Volume= 1mm Volume = 8mm Volume= 64mm3
12:2 ratio 6:2 ratio 3:2 ratio

6. Cell Cycle
Cell cycle – stages of growth, preparation, and division (Interphase and Mitosis)

7. Interphase
Interphase- period of normal growth and maintenance. (3 stages)
G1=growth
Synthesis=copy chromosomes
G2= maintenance.

8. Prokaryotic Chromosome
The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane
copyright cmassengale

9. Eukaryotic Chromosomes
All eukaryotic cells store genetic information in chromosomes
Most eukaryotes have between 10 and 50 chromosomes in their body cells
copyright cmassengale

10. DNA chromosome – wound DNAp (like DNA suitcases)
chromatin- unpackaged unwound DNA
Each cell has 46 chromosomes (23 from mom and 23 from dad).
Diploid – a cell with 2 set of chromosomes. (somatic cells)

11. copyright cmassengale
Karyotype
A picture of the chromosomes
First 22 pairs are called autosomes
Last pair are the sex chromosomes
copyright cmassengale

12. Mitosis
1 diploid parent cell splits into 2 identical diploid daughter cells.
Copied chromosomes made in synthesis are called sister chromatids… held together by centromeres.
chromosomes
Parent cell
Sister chromatids
identical daughter cells

13. Prophase
the chromosomes coil up and become visible while the nuclear envelope disappears. Sister chromatids are present.
A centriole forms at each pole and spindle fibers made of microtubules grow out.
Short microtubules stick out from the centriole in a star shape known as an aster.

14. Metaphase
Early in metaphase (prometaphase) spindle fibers attach to each of the chromatids at a sight called the kinetochore.
The spindle fibers line the chromatids up at the equator of the cell called the metaphase plate.
Kinetochore

15. Microtubules Chromosomes
Fig. 12-7
Aster
Centrosome
Sister
chromatids
Microtubules
Chromosomes
Metaphase
plate
Kinetochores
Centrosome
1 µm
Figure 12.7 The mitotic spindle at metaphase
Overlapping
nonkinetochore
microtubules
Kinetochore
microtubules
0.5 µm

16. Anaphase
Anaphase- During this phase, the kinetochores “reel in” or “gobble up” the spindle fibers to pull the sister chromatids apart by splitting their centromere.
The split chromatids are pulled towards opposite poles of the cell

18. Telophase
Once the chromatids have reached the opposite sides the spindle fibers disappear, the chromosomes unravel, and the nuclear envelope reappears on the two new nuclei.
In cytokinesis, the cytoplasm then forms a cleavage furrow at the equator to split the cytoplasm. (in plants a cell plate forms at the equator.)**
Two identical daughter cells are formed

20. Mitosis Vid
Mitosis

21. copyright cmassengale
Identify the Stages ?
Early, Middle, & Late Prophase ? ? ?
Metaphase
Anaphase
Late Prophase ? ? ?
Telophase & Cytokinesis
Late Anaphase
Telophase
copyright cmassengale

22. copyright cmassengale
Mitosis Quiz
copyright cmassengale

23. Why mitosis? Somatic cells divide for growth or maintenance.
What about reproduction?

24. Meiosis
1 diploid parent cell divides twice into 4 haploid unidentical daughter cells
Haploid – 1 set of chromosomes.
meiosis forms sperm or eggs called gametes . (gametes are haploid…1 set of 23 chromosomes)

25. Meiosis Forms Haploid Gametes
Meiosis must reduce the chromosome number by half
Fertilization then restores the 2n number
from mom
from dad
child
too
much!
meiosis reduces
genetic content
The right number!
copyright cmassengale

26. Prophase I
Homologous Chromosomes- a pair of chromosomes that have genes for the same trait (one from mom, one from dad)
During prophase I, Tetrads form. A tetrad is two homologous chromosomes made of sister chromatids linked together.
Homologous
chromosomes
Sister
chromatids
tetrad

27. Crossing over
These tetrads will trade genetic information in a process called crossing over. (new gene combinations form)

28. Metaphase I
During metaphase I tetrads are lined up at the equator of the cell.
Independent assortment- mom and dad’s chromosomes line up in any order.

29. Anaphase I, Telophase 1
During anaphase I, the tetrads are split into chromatids and pulled to opposite sides of the cell.
During telophase I the cell is split into two diploid cells.

30. Meiosis II 2nd Stage Meiosis II (P II, M II, A II, T II)
Prophase, metaphase, anaphase, telophase are repeated just like mitosis to split the chromatids into chromosomes.

31. copyright cmassengale
Meiosis Animation
copyright cmassengale

32. copyright cmassengale
Spermatogenesis
Occurs in the testes
produce 4 spermatids
Spermatids mature into sperm
Men produce about 250,000,000 sperm per day
copyright cmassengale

33. Spermatogenesis in the Testes
Spermatid
copyright cmassengale

34. copyright cmassengale
Spermatogenesis
copyright cmassengale

35. copyright cmassengale
Oogenesis
Occurs in the ovaries
Makes 3 polar bodies that die and 1 egg
Immature egg called oocyte
one oocyte matures into an ovum (egg) every 28 days
copyright cmassengale

36. Oogenesis in the Ovaries
copyright cmassengale

37. copyright cmassengale
Oogenesis
Oogonium
(diploid)
Mitosis
Primary
oocyte
Meiosis I
Secondary
(haploid)
Meiosis II
(if fertilization
occurs)
First polar body
may divide
Polar
bodies
die
Ovum (egg)
Second
polar body a A X
Mature
egg
copyright cmassengale

38. Why go through the Trouble?
Each parent produces new combinations of genes through crossing over, independent assortment and random fertilization.

39. Cancer
Cancer is when cells divide uncontrollably. They usually stop dividing when they touch other cells.