CSB328H1 Study Guide - Midterm Guide: Heparan Sulfate, Interphase, Lateral Plate Mesoderm
8 Jun 2018
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CSB328
Lecture 1 – Model systems (p1: 1-3; ch1:15-17)
• Life starts as one cell
o Ends up as a complex organism
▪ How?
o Processes of development
▪ Axis formation
▪ Specification
▪ Differentiation
▪ Growth
▪ Regulation of structures
▪ Organ creation
▪ Organization of cells and tissues
o How do we examine developmental processes?
• Model organisms
o Organisms that are easily observable with regards to some aspect of development
▪ Large eggs
• Easily manipulated (injection, tissue transplant)
▪ Clear eggs
• Easily observed
• Chicken eggs can have the shell delicately removed, enabling
observation
▪ External development
• Easier to see ithout stikig a aera up soe orgais’s
reproductive system
▪ Many eggs produced
• Easy to check different stages, have many controls/experimental
subjects, large sample size
▪ Rapid development
• Not much waiting
▪ Short life cycle
• Allows for genetic analysis through generations
▪ Small
• Cheap, easy to keep, able to be lab-bred
o Examples
▪ Chicken, zebrafish, mice, Drosophila
▪ Xenopus
• A type of frog
• Large eggs, hundreds at a time
o 1.2 millimeter eggs
• Opaque eggs and embryo
• Rapid, external development
o Embryo develops in 4 days
find more resources at oneclass.com
find more resources at oneclass.com
• Cheap, easy to breed, large
o Adult frogs are 10-13 cm long
• Egg to adulthood in two months, sexual maturity in six
• Easy genetic manipulation but not much genetic transfer
o Slow generations
▪ C. elegans
• Nematode worm
• Micron-scale eggs, hundreds in hundreds at a time
o 50 micrometer
• External development, life cycle of 3 days
o 15 hours for embryo to develop
• Cheap, easy to breed
• Easy genetic manipulation
o Highly developed genetics, quick generations
• Vo Baer’s las
o The general features appear in the embryo before the specialized features
▪ All vertebrates have spinal cords at the early point, but wings/arms/etc. come
later
o Development follows a gradient from more general to specialized
▪ All vertebrates start off with identical skin, then scales/feathers/hair develop
o The embryo of a given species departs more and more from adult lower animals
▪ We do’t hae to look like adult fish, irds ad reptiles i our eros
o The early embryo of a higher animal is only like itself
▪ Embryos diverge instead of following transitions
Lecture 2 – Cleavage, fate (ch1: 6-8, 19-23; ch5:158-159; ch8:241-244)
• Frog egg
o Fertilized egg = zygote
▪ Unfertilized = oocyte
o Two poles
▪ Animal pole
• Pigment, little yolk
• Sperm enters at specific spot in animal pole
▪ Vegetal pole
• No pigment, much yolk
o Covered in layers
▪ Vitelline membrane
▪ Gelatinous coat
o Cellular cleavage
▪ Cleavage divisions = early embryonic cell divisions
▪ Blastomere = early embryonic cells that undergo cleavage divisions
▪ 1st cleavage = 2 blastomeres
• Each is half animal, half vegetal
▪ 2nd cleavage = 4 blastomeres
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find more resources at oneclass.com
• Each is half and half again
▪ Types of cleavage
• Holoblastic
o Complete cell cleavage
o Distribution of yolk is such that cleavage is not terribly impeded
o Amphibians, etc.
• Meroblastic
o Incomplete cell cleavage
o Yolk impedes cleavage due to its structure
▪ Continue division
▪ Morula
• 16-64 cells (4th – 6th divisions)
• Looks like a mulberry, whatever those look like
▪ Blastula
• 128+ cells (12+ divisions)
• Has a cavity under the animal pole called the blastocoel
o Axes
▪ Dorsal/ventral
• Belly and back
▪ Anterior/posterior
• Forwards and backwards
o Fate mapping
▪ Figure out relationship between regions of blastula and tissues of embryo
▪ A fate map
• A diagram that shows what each region of the embryo will become
during normal development
o Where it will move
o How it will change shape
o What it will become
▪ The process
• Vogt’s proess
o Get a gel chip with Nile blue dyed agar chips, put it on one
specific spot on a blastula
▪ Vital dye
• Nile blue
• Color is real, dilutes over time
▪ Fluorescent dye
• Fluorescein-conjugated dextran
• Can still be detected many generations in
▪ Genetic marker
• Track different genetic makeup
• Like pigmented/unpigmented cell-producing
DNA (Spemann-Mangold)
▪ Transgenic fluorescence
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 1 model systems (p1: 1-3; ch1:15-17) Incomplete cell cleavage: yolk impedes cleavage due to its structure, continue division, morula, 16-64 cells (4th 6th divisions) Dna (spemann-mangold: transgenic fluorescence, use a virus to infect embryonic cells with a fluorescent protein (ex. If cells with different fates mix due to random movement, the result is overlapping of fates: gastrulation, formation of three germ layers, ectoderm, top (animal pole, skin, nervous system. Labile state: specified if tissue develops in isolation into that which was predicted by fate map. If (cid:374)ot, the tissue has(cid:374)"t (cid:271)ee(cid:374) spe(cid:272)ified: determination locks the cell into developing that fate, stable state, determined if tissue develops after heterotropic transplant into that which was predicted by fate map. Late gastrula: neural tissue becomes neural, epidermis is therefore the default ectodermal fate without intervention to make it neural, transplant cells from one region to another. Isolation experiment: then they have no other influences.
