Lecture #10: Development Flashcards
What does N mean?
number of chromosomes in a species
How many chromosomes do humans have?
46 total, 23 from mom and 23 from dad
N for fruit flies?
N = 4
N for humans?
N = 23
Egg
1N (Haploid)
Sperm
1N (Haploid)
What does Egg + Sperm create?
Zygote
Zygote
2N (Diploid)
- 2 sets of chromosomes
Path of development from zygote to adult
Zygote (2N, Dipole) -> Blastole -> Gastrula -> Neural tube -> Juvenile -> adult (mostly 2N)
Parts of sperm?
Flagellum, Haploid nucleus, Acrosor, Mitochondria
Acrosomal reaction
- Enzymes in Acrosor allow sperm to contact the egg cell membrane
- Reaction between sperm proteins and egg membrane protein for membranes to fuse
- if sperm is from another species, reaction will NOT occur
- sperm nucleus is introduced into egg
Blocks to polyspermy?
- Fast-block - Na+ ion enters egg, wave of electrical potential prevents 2nd sperm from entering
- Slow-block - Cortical grandules dumped between cell membranes and vitelline membrane
Steps in Fertilization
- combine set of chromosomes from egg with sperm
- Block polyspermy
- initiates cell division in egg
Deuterostomes
vertebrates
- Anus forms before mouth forms
Echinoderms
sea star + sea urchin
Protestones
most invertebrates
- mouth forms before anus
Stem cell
a cell that can be used to regenerate new cells
Embryonic stem cells
totipotent
Totipotent
cell that can become any structure in body or extra-embryonic structures
Pluripotent
cells that can become any structure in body
Multipotent
a cell that can become a number of different structures
Adult stem cells
multipotent
Egg developement
Ferilized egg -> clevege decisions -> 4-cell -> 8-cell -> Blastula -> Gastrula -> Mid/late Gastrula
Blastula
ball of cells
Gastrula
has a blastopore (hole)
- blastopore eventualy becomes anus
Mid/late gastrula
- Ectoderm
- Mesoderm
- Endodertm
Ectoderm
Becomes skin + nervous system
Mesoderm
- Multipotent stem cells -> Myeloid stem cells -> Red blood cells + macrophage
- Lymphoid stem cell -> T cell and B cells (in immune systems)
- becomes blood, bone, muscle cells, etc
Endoderm
Becomes most of digestive systems
Induction
One group of embryonic cells influencing the fate of another group of cells, usually by tactile (touch) or chemical communication between cells
Neural tube
embryonic structure that forms the brain and spinal cord (produced by folding of ectoderm)
Notochord
A rod of cartilage that supports the body in all embryos and some adult vertebrates
At what stage of development do we see the formation of the archenteron?
Gastrule
