1. Genetics and Development
AP Biology
Genetics and Development

2. Important concepts from previous units:
Genes are segments of DNA that are the “blueprints” for making proteins and enzymes within cells.

3. Zygote (One 2n cell that is the result of a 1n sperm fertilizing a 1n egg.)
This cell will give rise to over two hundred different human cells all with the 100% identical genome within them during development.

4. Morphogenesis over time
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

5. Cell Differentiation (A. K.A. Specialization.)
Expressing different genes makes cells different or specialized in function and shape.
Specialized functions are the products of “adult” cells.

6. Specialized Epithelial tissue See the DIFFERENT shapes?

7. Specialization Nervous Tissue

8. Morphogenesis (“morph” means “body shape”; “genesis” means “creation of”)
The process of morphogenesis is the product of cell differentiation occurring during development.
Apoptosis (Programmed cell death) is a crucial part of development too. (For example, apoptosis helps to “create” the spaces between your fingers and toes by “killing off” those cells in the webbing.)

9. Apoptosis “Programmed Cell Death… it’s in the DNA.”

10. Morphogenesis in plants:
The cells of plants do not move as they are restricted by the cell wall. They mature in place and respond to environmental cues.
Plants display continual growth until they die. (The growth occurs at the Apical Meristem. These tissues are found at the tips of roots and stems.)

11. Morphogenesis in Plants

12. Morphogenesis in animals:
The cells of animals move into their final position during development.
Animal display limited growth. (They die after a certain number of years.)

13. Morphogenesis in Animals

14. Cloning and Clones
Cloning is the process of making 100% genetically identical organisms called Clones.

15. Animal Cloning First step: Remove an egg cell from a female organism.
This cell has all the enzymes and machinery to make development possible.
Second Step: Remove the Haploid nucleus from the egg cell.
Third Step: Take a somatic cell nucleus (Diploid) out of a somatic cell and put it in the egg cell.
Fourth Step: Put the “egg” cell in a surrogate organism (female) to develop until birth.

16. Cloning of Dolly
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
Ian Wilmut and Dolly (1997)
He was the first to develop this process of cloning. Dolly was the name of the first cloned sheep.
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

17. Stem cells
These animal cells are said to be Pluripotent. (They can become any type of cell.)(“pluri” means “many”)
These cells have many possibilities as to what they will develop into as they develop.
They are said to be “embryonic” in development. They also have no genes “locked up”; therefore they can make any protein or enzyme.

18. Origins of stem cells. (Embryonic vs. Adult)
Embryonic are found in developing embryos and adult stem cells are found within developed tissues.
The difference is that adult stem cells have undergone a small amount of differentiation and therefore CANNOT make every protein/enzyme and therefore are limited in what type of cell they can become.
Embryonic stem cells have NOT undergone ANY differentiation. They CAN make every protein/enzymes.

19. Embryonic Stem Cells (These have pluripotential – they can become any type of cell.)

20. Research?
Embryonic stem cells are more valuable in research because of the unlimited possibilities.
They could cure diseases such as Diabetes or SCIDS, repair spinal cord injuries, or be used to grow new organs for transplants

21. 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

22. cytoplasmic determinant.
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

23. Stem cells communicating using ligand molecules.
Early embryo
(32 cells)
Signal
transduction
pathway
NUCLEUS
Signal
receptor
Signal
molecule
(inducer)
Stem cells communicating using ligand molecules

24. Pattern Formation
DNA information (genes) that controls the development of the species’ “Pattern”.
Each species is unique to an extent in the “pattern” and DNA sequences that creates it.

25. Pattern Formation for Plants

26. Pattern Formation

27. Pattern Formation

28. Positional Information
The cell “position” is accomplished through cell-to-cell communication.
Where in relation to the whole organism?
What is next to it?

29. Positional Information

30. Maternal Effect Genes (A.K.A. Egg Polarity Genes)
Controlling the polarity of the Zygote helps to determine the Head and Tail or Root and Shoot.
This “control” is accomplished by production of cytoplasmic determinant proteins and morphogens (Proteins that affect morphogenesis.)
They will accumulate on one side of the zygote cell. This accumulation determines the poles of the cell and what each end will start development of in the organism.
They are referred to as “maternal” because they are produced in the female egg cell.

31. Maternal Effect and Zygote Polarity
Animal pole
Vegetal
hemisphere
Vegetal pole
Point of
sperm entry
Animal

32. Segmentation Genes
These genes produce proteins that influence what will happen in a particular segment of an organism.
Best examples are insects and crustaceans.

33. Segment Genes Adult fruit fly Fruit fly embryo (10 hours) Fly
chromosome
Mouse
chromosomes
Mouse embryo
(12 days)
Adult mouse

34. Homeotic Genes (A.K.A. Hox genes)
These genes are the master control genes for an organism’s development. These are the most important genes in any organism… as the control total development from start to finish.)
They contain the Homeobox (A unique DNA nucleotide sequence.)
It is a 180 Nucleotide sequence found in Hox genes.
Evolution? The more similar the sequence between organisms; the more closely related in terms of evolution they are. The more different the sequence; they less related they are.

35. THE DIFFERENCE BETWEEN HOMEOBOX AND HOX GENES

36. Homeotic Genes
“Put the head here! Legs go over there!”

37.
Hox genes code for proteins that attach to molecular switches on DNA, turning other genes on and off. The DNA-binding piece of a Hox protein is called the homeodomain, and it's encoded by the homeobox. The homeodomains in different Hox proteins are similar but not identical—they bind to different DNA sequences. So different Hox proteins regulate different sets of genes, and combinations of Hox proteins working together to regulate still other sets of genes.
As regulators of other genes, Hox proteins are very powerful.
A single Hox protein can regulate the activity of many genes. And sets of genes work together to carry out "programs" during embryonic development—programs for building a leg or an antenna, for example—much like computer programs carry out specific tasks.

38. Hox Genes