1. Reproduction & Development

2. LE 21-4 Animal development Gut Cell movement Zygote (fertilized egg)
Eight cells
Blastula
(cross section)
Gastrula
(cross section)
Adult animal
(sea star)
Cell division
Morphogenesis
Observable cell differentiation
Plant development
Seed
leaves
Shoot
apical
meristem
Root
apical
meristem
Zygote
(fertilized egg)
Two cells
Embryo
inside seed
Plant

3. Differentiation
Differences between cells come from gene expression, not differences in the cells’ genomes
as regulatory mechanisms turn genes off and on

4. Reproductive Cloning of Mammals
Dolly
a lamb cloned from an adult sheep
nuclear transplantation from a differentiated mammary cell
premature death in 2003
arthritis
speculation that her cells were “older” than those of a normal sheep

5. LE 21-7 Mammary cell donor Egg cell donor Egg cell from ovary Nucleus
removed
Cells fused
Cultured
mammary cells
are semistarved,
arresting the cell
cycle and causing
dedifferentiation
Nucleus from
mammary cell
Grown in culture
Early embryo
Implanted in uterus
of a third sheep
Surrogate
mother
Embryonic
development
Lamb (“Dolly”) genetically identical
to mammary cell donor

6. mice, cats, cows, horses, and pigs are now cloned
“Copy Cat”

7. Problems Associated with Animal Cloning
small percentage of cloned embryos have develop normally to birth

8. The Stem Cells of Animals
Embryonic stem cells
isolated from early embryos at the blastocyst stage
Totipotent
able to differentiate into all cell types
Adult stem cells
replace nonreproducing specialized cells
Pluripotent
able to give rise to multiple but not all cell types

9. LE 21-9 Embryonic stem cells Adult stem cells Totipotent cells
Pluripotent
cells
Cultured
stem cells
Different
culture
conditions
Different
types of
differentiated
cells
Liver cells
Nerve cells
Blood cells

10. Gene Expression During Development
Tissue-specific proteins
enable differentiated cells to carry out their specific tasks

11. LE 21-10_1 Nucleus Master control gene myoD
Other muscle-specific genes
DNA
Embryonic
precursor cell
OFF
OFF

12. LE 21-10_2 Nucleus Master control gene myoD
Other muscle-specific genes
DNA
Embryonic
precursor cell
OFF
OFF
Determination
mRNA
OFF
MyoD protein
(transcription
factor)
Myoblast
(determined)

13. LE 21-10_3 Nucleus Master control gene myoD
Other muscle-specific genes
DNA
Embryonic
precursor cell
OFF
OFF
Determination
mRNA
OFF
MyoD protein
(transcription
factor)
Myoblast
(determined)
Differentiation
mRNA
mRNA
mRNA
mRNA
Myosin, other
muscle proteins,
and cell-cycle
blocking proteins
MyoD
Another
transcription
factor
Muscle cell
(fully differentiated)

14. Cell Signals in Cell Differentiation
cytoplasmic determinants
Maternal substances that influence early development
regulate expression of genes that affect the cell’s developmental fate
Induction
signal molecules from embryonic cells cause transcriptional changes in nearby target cells

15. cytoplasmic determinant
LE 21-11a
Unfertilized egg cell
Sperm
Molecules of another
cytoplasmic determinant
Molecules of a
cytoplasmic
determinant
Nucleus
Fertilization
Zygote
(fertilized egg)
Mitotic cell division
Two-celled
embryo
Cytoplasmic determinants in the egg

16. Induction by nearby cells
LE 21-11b
Early embryo
(32 cells)
Signal
transduction
pathway
NUCLEUS
Signal
receptor
Signal
molecule
(inducer)
Induction by nearby cells

17. Apoptosis
programmed cell death

18. LE 21-19
Interdigital tissue
1 mm

19. Mechanisms of Plant Development
Embryonic development
Within the seed
Meristems
cell division, morphogenesis, and differentiation give rise to new organs
i.e. apical meristems
at the tips of shoots
Site of height growth

20. Pattern Formation in Flowers
floral meristem
Participate in forming a flower
carpels
contain egg cells
stamens
contain sperm-bearing pollen
Petals
Sepals
Leaflike structures outside the petals

21. LE 21-20
Carpel
Stamen
Petal L1
Cell
layers L2 L3
Sepal
Floral meristem
Anatomy of a flower
Tomato flower

22. LE 21-22
Wild type
Mutant

23. Conservation of developmental genes
LE 21-23
Adult
fruit fly
Fruit fly embryo
(10 hours)
Fly
chromosome
Mouse
chromosomes
Mouse embryo
(12 days)
Adult mouse

24. LE 21-24
Genital
segments
Thorax
Abdomen
Thorax
Abdomen