1. Cellular Reproduction
Chapter 9

2. The larger the cell, the more difficult it is
Limits of Cell Growth:
The larger the cell, the more difficult it is
for materials to enter and leave it.
Rates of Cell Growth:
E. coli can double its volume in = 30 minutes.
In one day, a single cell would grow into a 14 kg mass of
bacteria. In 3 days = mass of the earth

3. Controls on Cell Growth: cells of the heart and
nervous system rarely grow. Cells of the skin and
digestive tract grow and divide rapidly throughout
Life; old, worn out, and damaged cells. Cells will
grow until they come into contact with each other.
Uncontrolled Cell Growth:
Cancer cells grow out of control
until they have used up all of their nutrients

4. Chromosomes: Made up of chromatin (DNA and protein)
Total length of DNA is = 10,000 x length of the chromosome.
In 1973, Don and Ada Olins and Christopher Woodcock discovered the chromosome’s DNA was coiled around special proteins called histones.
DNA and histone molecules form beadlike structures called nucleosomes.
Nucleosomes form a thick fiber, shortened by a system of loops and coils.

5. Chromosome Structure
Composed of 2 sister chromatids and a centromere.

6. Binary Fission of a Prokaryote

7. The Cell Cycle
Is the period from the beginning of one mitosis to the beginning of the next
Consists of interphase and M phase

8. Prophase
Metaphase
Anaphase
Telophase
Interphase

9. Controls On The Cell Cycle

10. Interphase

11. Interphase Is a period of intense activity Proteins are made
DNA copied
ATP is made and utilized
Nucleus is synthesizing mRNA to direct cellular activities

12. Interphase Consists of G1, S, and G2
Cells do not move through the cycle at the same rate
G1 consists of cell growth and development; increase in supply of proteins, and synthesis of some organelles
S stands for synthesis: DNA replication occurs here
G2 synthesis of more organelles and the cell prepares for mitosis (shortest of the phases)

13. Mitosis Division of the nucleus Occurs in somatic or body cells
Can last from a few
minutes to several
days

14. Mitosis Diagram

15. Prophase (longest phase)
Chromosomes become visible as they shorten and thicken
Disintegration of the nucleolus and the nuclear envelope
Centrioles move apart
Formation of the mitotic spindle fibers
Takes up about 50-60%
of mitosis

16. Metaphase (shortest phase)
Centrioles have reached the opposite poles
Chromosomes line up along the equator or middle of the cell
Centromere of each chromosome is attached to a spindle fiber

17. Anaphase (3rd phase) Centromeres split
Spindle fibers draw chromatids to poles of cells
Chromatids are now individual chromosomes

18. Telophase Chromosomes have reached opposite poles
Chromosomes uncoil and become less distinct
Nuclear membrane begins to reform around chromosomes
Spindle begins to break apart
Nucleolus reappears
Cells begin to divide by formation of cell plate in plant cells and cleavage furrow in animal cells
Formation of two new daughter cells

19. Telophase (final phase)

20. Cytokinesis Division of the cytoplasm Occurs at the end of telophase
Results in two identical daughter cells

21. Review of Mitotic Stages

22. Meiosis
The process of gamete formation in which the chromosome number is reduced to half the normal number
Requires two nuclear divisions called Meiosis I and Meiosis II

23. Meiosis I Interphase-the cell replicates its chromosomes
Prophase I-each pair of homologous chromosomes comes together to form a four-part structure called tetrad
Crossing Over-homologous chromosomes exchange genetic material
Metaphase I-homologous chromosomes line up in tetrads independently of each other
Anaphase I-centromeres do not split, this ensures that each new cell will receive only one chromosome from each homologous pair
Telophase I-each new cell has one half of the genetic information

24. Crossing over Pairing of homologous chromosomes Chiasma formation
Breakage
and joining
Recombinant

25. Crossing Over Animated

26. Metaphase I
Anaphase I
Telophase I
Prophase II
Prophase I

27. Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II

28. Result of Meiosis
4 Haploid cells Gametes

29. Meiosis begins by replicating the chromosomes

30. Centromeres Do Not Split at Meiosis I

31. Centromeres Split at Meiosis II

32. Oogenesis Process by which egg cells are made
Results in four haploid gametes
One functional ovum capable of fertilization
Three polar bodies disintegrate

33. Spermatogenesis Process by which sperm cells are produced
Results in four functional sperm cells

34. MITOSIS Somatic cells MEIOSIS Cells in sexual cycle
1 cell division:
2 daughter cells 2n 2n
MEIOSIS
Cells in sexual cycle
2 cell divisions:
4 product of meiosis n n 2n n n
n=chromosome number

35. Final result Mitosis : two genetically identical diploid cells
from one diploid parent cell
Diploid organism: two sets of chromosomes (one
from each parent); 2n
Mitosis
Conservative process:
Daughter cells genotypes identical
to parental genotypes

36. Four genetically different haploid cells; from one diploid parent cell
Meiosis :
Four genetically different haploid cells; from one diploid parent cell
Haploid organism: one set of chromosomes; n
Meiosis
Promotes variation among the product
of meiosis (crossing over)

37. Mitosis vs Meiosis Alike Both have the stages PMAT
Both go through Cytokinesis
Both divide and make daughter cells
Both are a form of reproduction
Both take place inside the cell
Chromosomes duplicate and DNA replication occurs in each process
Different
Mitosis produces two identical daughter cell, meiosis produces four genetically different cells
Crossing over and tetrad formation (synapsis) occur in prophase I of Meiosis
The centromeres split in Anaphase II
Mitosis has one division, Meiosis has two
Mitosis occurs in somatic or body cells
Meiosis occurs in reproductive organs; producing gametes
Mitosis is asexual reproduction
Meiosis ensures sexual reproduction