1. The Cellular Basis of Reproduction and Inheritance
Chapter 8
The Cellular Basis of Reproduction and Inheritance

2. Rain Forest Rescue
Scientists in Hawaii are attempting to "rescue" endangered species from extinction by promoting reproduction
Reproduction is one phase of an organism's life cycle
Sexual reproduction
Fertilization of sperm and egg produces offspring, combining genetic material from both parents

3. Cell division is at the heart of organismal reproduction
Asexual reproduction
Offspring are produced by a single parent, without the participation of sperm and egg…essentially producing clones
Cell division is at the heart of organismal reproduction

4. 8.1 CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION
Like begets like, more or less
Asexual reproduction
Chromosomes are duplicated and cell divides
Each daughter cell is genetically identical to the parent and the other daughter
Sexual reproduction
Each offspring inherits a unique combination of genes from both parents
Offspring can show great variation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

5. Cells arise only from preexisting cells
Section 8.2
Cells arise only from preexisting cells
"Every cell from a cell" is at the heart of the perpetuation of life
Can reproduce an entire unicellular organism
Is the basis of sperm and egg formation
Allows for development from a single fertilized egg to an adult organism
Functions in an organism's renewal and repair

6. Prokaryotes reproduce by binary fission
Section 8.3
Prokaryotes reproduce by binary fission
Prokaryotic cells reproduce asexually by a type of cell division called binary fission
Genes are on one circular DNA molecule
The cell replicates its single chromosome
The chromosome copies move apart
The cell elongates
The plasma membrane grows inward, dividing the parent into two daughter cells

7. LE 8-3a Prokaryotic Plasma chromosome membrane Cell wall
Duplication of chromosome
and separation of copies
Continued elongation of the
cell and movement of copies
Division into
two daughter cells

8. 8.4 THE EUKARYOTIC CELL CYCLE AND MITOSIS
The large, complex chromosomes of eukaryotes duplicate with each cell division
Eukaryotic genes
Many more than in prokaryotes
Grouped into multiple chromosomes in the nucleus

9. Eukaryotic chromosomes
Contain a very long DNA molecule associated with proteins
Most of the time occur in the form of thin, loosely packed chromatin fibers
Condense into visible chromosomes just before cell division

10. Eukaryotic cell division Chromosomes replicate
Sister chromatids joined together at the centromere
Sister chromatids separate
Now called chromosomes
Cell divides into two daughter cells
Each with a complete and identical set of chromosomes

11. LE 8-4c Chromosome duplication Sister chromatids Centromere Chromosome
distribution to
daughter
cells

12. The cell cycle multiplies cells
Section 8.5
The cell cycle multiplies cells
The cell cycle is an ordered series of events extending from the time a cell is formed until it divides into two
Most of the cell cycle is in interphase
G1: cell grows in size
S: DNA synthesis (replication) occurs
G2: Cell continues to grow and prepare for division

13. The cell actually divides in mitotic (M) phase
Mitosis: nuclear division
Cytokinesis: cytoplasmic division
Duplicated chromosomes evenly distributed into two daughter nuclei

14. S (DNA synthesis) Cytokinesis Mitosis INTERPHASE G1 G2 MITOTIC LE 8-5
PHASE (M)

15. Cell division is a continuum of dynamic changes
Section 8.6
Cell division is a continuum of dynamic changes
Interphase: Duplication of the genetic material ends when chromosomes begin to become visible
Prophase (the first stage of mitosis): The mitotic spindle is forming. Centrosomes migrate to opposite ends of the cell
Prometaphase: Chromatins completely coil into chromosomes; nucleoli and nuclear membrane disperse

16. Metaphase: The spindle is fully formed; chromosomes are aligned single file with centromeres on the metaphase plate
Anaphase: Chromosomes separate from the centromere, dividing to arrive at poles
Telophase: Cell elongation continues, a nuclear envelope forms around chromosomes, chromosomes uncoil, and nucleoli reappear
Cytokinesis: The cytoplasm divides

17. LE 8-6a LM 250  INTERPHASE PROPHASE PROMETAPHASE Early mitotic
spindle
Fragments
of nuclear
envelope
Centrosomes
(with centriole pairs)
Centrosome
Chromatin
Kinetochore
Nucleolus
Nuclear
envelope
Plasma
membrane
Chromosome, consisting
of two sister chromatids
Centromere
Spindle
microtubules

18. LE 8-6b Metaphase plate Cleavage furrow Nucleolus forming Nuclear
ANAPHASE
TELOPHASE AND CYTOKINESIS
Metaphase
plate
Cleavage
furrow
Nucleolus
forming
Nuclear
envelope
forming
Daughter
chromosomes
Spindle

19. Animation: Cytokinesis
Section 8.7
Cytokinesis differs for plant and animal cells
Animals
Ring of microfilaments contracts into cleavage furrow
Cleavage occurs
Plants
Vesicles fuse into a membranous cell plate
Cell plate develops into a new wall between two daughter cells
Animation: Cytokinesis

20. LE 8-7a Cleavage furrow Cleavage furrow Cleavage furrow
SEM 140
Cleavage furrow
Contracting ring of
microfilaments
Daughter cells

21. LE 8-7b TEM 7,500 Cell plate forming Wall of parent cell Daughter
nucleus
TEM 7,500
Cell wall
New cell wall
Vesicles containing
cell wall material
Cell plate
Daughter cells

22. Section 8.7
Anchorage, cell density, and chemical growth factors affect cell division
An organism must be able to control the timing of cell division
Anchorage dependence
Most animal cells must be in contact with a solid surface to divide

23. Density-dependent inhibition
Cells form a single layer
Cells stop dividing when they touch one another
Inadequate supply of growth factor causes division to stop

24. LE 8-8a Cells anchor to dish surface and divide. When cells have
formed a complete
single layer, they
stop dividing
(density-dependent
Inhibition).
If some cells are
scraped away, the
remaining cells
divide to fill the dish
with a single layer
and then stop
(density-dependent
inhibition).

25. After forming a single layer, cells have stopped dividing.
LE 8-8b
After forming a
single layer,
cells have
stopped dividing.
Providing an
additional supply of
growth factors
stimulates
further cell division.

26. Growth factors signal the cell cycle control system
Section 8.9
Growth factors signal the cell cycle control system
The cell cycle control system regulates the events of the cell cycle
If a growth factor is not released at three major checkpoints, the cell cycle will stop
G1 of interphase
G2 of interphase
M phase

27. G0 S G1 G2 M LE 8-9a G1 checkpoint Control system M checkpoint

28. How a growth factor might affect the cell cycle control system
Cell has receptor protein in plasma membrane
Binding of growth factor to receptor triggers a signal transduction pathway
Molecules induce changes in other molecules
Signal finally overrides brakes on the cell cycle control system

29. Growth factor Plasma membrane Relay proteins Receptor protein
LE 8-9b
Growth factor
Plasma membrane
Relay
proteins
Receptor
protein
G1 checkpoint
Signal
transduction
pathway
Control
system G1 S M G2

30. Growing out of control, cancer cells produce malignant tumors
Section 8.10
Growing out of control, cancer cells produce malignant tumors
Cancer cells do not respond normally to the cell cycle control system
Divide excessively
Can invade other tissues
May kill the organism

31. If an abnormal cell avoids destruction by the immune system, it may form a tumor
Benign: abnormal cells remain at original site
Malignant: abnormal cells can spread to other tissues and parts of the body
Metastasis: spread of cancer cells through the circulatory system

32. LE 8-10 Lymph vessels Tumor Blood vessel Glandular tissue
A tumor grows from a
single cancer cell.
Cancer cells invade
Neighboring tissue.
Cancer cells spread through
lymph and blood vessels to
other parts of the body.

33. Cancers are named according to location of origin
Carcinoma: external or internal body coverings
Sarcoma: tissues that support the body
Leukemia and lymphoma: blood-forming tissues
Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division

34. Section 8.11
Review of the functions of mitosis: growth, cell replacement, and asexual reproduction
When the cell cycle operates normally, mitotic cell division functions in
Growth
Replacement of damaged or lost cells
Asexual reproduction
Video: Hydra Budding

36. 8.12: MEIOSIS AND CROSSING OVER
Chromosomes are matched in homologous pairs
The somatic (body) cells of each species contain a specific number of chromosomes
Humans and most other organisms have pairs of homologous chromosomes
Carry genes for the same characteristics at the same place, or locus
Except sex chromosomes
One chromosome is inherited from the female parent, one from the male

37. LE 8-12
Chromosomes
Centromere
Sister chromatids

38. Gametes have a single set of chromosomes
Section 8.13
Gametes have a single set of chromosomes
Diploid cells have two sets of chromosomes (2n)
Somatic cells
Haploid cells have one set of chromosomes (n)
Gametes (egg and sperm cells)
Sexual life cycles involve the alternation of haploid and diploid stages
Fusion of haploid gametes in fertilization forms a diploid zygote

39. LE 8-13 (2n = 46) Haploid gametes (n = 23) n Egg cell n Sperm cell
Meiosis
Fertilization
Diploid
zygote
(2n = 46) 2n
Multicellular
diploid adults
(2n = 46)
Mitosis and
development

40. Meiosis reduces the chromosome number from diploid to haploid
Section 8.14
Meiosis reduces the chromosome number from diploid to haploid
Meiosis
Like mitosis, is preceded by chromosome duplication
Unlike mitosis, cell divides twice to form four haploid daughter cells

41. The process of meiosis includes two consecutive divisions Meiosis I
In synapsis, homologous chromosomes are paired
In crossing over, homologous chromosomes exchange corresponding segments
Each homologous pair divides into two daughter cells, each with one set of chromosomes consisting of two chromatids

42. Meiosis II
Essentially the same as mitosis
Sister chromatids of each chromosome separate
Result is four cells, each with half as many chromosomes as the parent

43. LE 8-14a Microtubules attached to kinetochore Centrosomes
MEIOSIS I
: Homologous chromosome separate
INTERPHASE
PROPHASE I
METAPHASE I
ANAPHASE I
Microtubules
attached to
kinetochore
Centrosomes
(with centriole
pairs)
Metaphase
plate
Sister chromatids
remain attached
Sites of crossing over
Spindle
Nuclear
envelope
Sister
chromatids
Tetrad
Centromere
(with kinetochore)
Homologous
chromosomes separate
Chromatin

44. LE 8-14b Haploid daughter Sister chromatids cells forming separate
MEIOSIS I
: Sister chromatids separate
TELOPHASE I
TELOPHASE I
PROPHASE I
METAPHASE I
ANAPHASE I
AND CYTOKINESIS
AND CYTOKINESIS
Cleavage
furrow
Sister chromatids
separate
Haploid daughter
cells forming

45. Review: A comparison of mitosis and meiosis
Section 8.15
Review: A comparison of mitosis and meiosis
Mitosis
Provides for growth, tissue repair, and asexual reproduction
Produces daughter cells genetically identical to the parent
Meiosis
Needed for sexual reproduction
Produces daughter cells with one member of each homologous chromosome pair

46. (before chromosome replication)
LE 8-15
MITOSIS
MEIOSIS
Parent cell
(before chromosome replication)
Site of
crossing over
MEIOSIS I
Prophase I
Prophase
Duplicated
chromosome (two
sister chromatids)
Chromosome
replication
Chromosome
replication
Tetrad formed
by synapsis of
homologous
chromosomes
2n = 4
Chromosomes
align at the
metaphase plate
Tetrads
align at the
metaphase plate
Metaphase
Metaphase I
Anaphase
Telophase
Sister chromatids
separate during
anaphase
Anaphase I
Telophase I
Homologous
chromosomes
separate during
anaphase I;
sister
chromatids
remain together
Haploid
n = 2
Daughter
cells of
meiosis I
No further
chromosomal
replication;
sister
chromatids
separate during
anaphase II 2n 2n
MEIOSIS I
Daughter cells
of mitosis n n n n
Daughter cells of meiosis II

47. Animation: Genetic Variation
Section 8.16
Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring
Reshuffling of the different versions of genes during sexual reproduction produces genetic variation
Random arrangements of chromosome pairs at metaphase I of meiosis lead to many different combinations of chromosomes
Random fertilization of eggs by sperm greatly increases this variation
Animation: Genetic Variation

48. LE 8-16 Possibility 1 Possibility 2 Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Gametes
Combination 1
Combination 2
Combination 3
Combination 4