MCB 150 Study Guide - Midterm Guide: Maternal Effect, Vitelline Membrane, Acrosome Reaction

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How does the body rise from a fertilized egg
1. Preformation: we are already formed and we just grow bigger (person in sperm)
2. Epigenesist: structures arise de novo during embryogenesis
Development is a step wise process
Single cell embryo -> blastula -> gastrula -> organogenesis
Stages of cell commitment
Specification: cell can autonomously without signals, form a certain cell type **reversible
Determination: cell can autonomously form a certain cell type even in a non-neutral
environment **NON reversible
Differentiation: process by which an unspecialized cell becomes specialized
Stages of development
1. Gametogenesis: making of gametes
2. Fertilization: fusing the gametes
3. Cleavage: cell division to partition the zygote (blastula)
4. Gastrulation: organizing into the three primary layers (ectoderm, mesoderm, endoderm)
5. Organogenesis: generating organs
Positive control => control that is supposed to work when the experiment is successful
Negative control => control to show that the experiment indeed tested for what they wanted it to test;
gives a negative result when the experiment is done correctly
Experiment to show differentiated cells still have all genetic material to produce new organisms
Frog oocyte => enucleated
Epithelial frog cell => nucleus taken => added to the enucleated oocyte
new oocyte is grown to see if it can make a complete new organism.
Result: It can. Therefore, differentiated cells do have all the genetic materials
Positive control: oocyte is of a green frog; epithelial is from an albino mutant => if new organism
grown is albino, it is from the genetic material of the epithelial
Another Positive control: put nuclei from other oocytes into the enucleated oocyte.
Theoretically this should be able to produce viable embryo
Negative control: only put buffer into the oocyte to make sure that the new organism CANNOT
be grown by the denucliated oocyte
Fate maps: shows the process of cell lineage from the precursor cell into the adult organism; shows
what each cell becomes differentiated into
First fate map done was of C. elegans
Very simple organism and you can follow along the entire division process by a microscope
More complex organisms
Vital dye marking
Florescence dye infection
Cell transplantation from one similar species to another
Then use indirect immunostaining
iPSCs: induced pluripotent cells => can use your own genes to reprogram and make iPSCs for other
function
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potentially used in treatment and making organs or self-donation
Experimental method: RNA in situ hybridization
Purpose: determine in what cells a particular RNA is expressed
Use complementary sequence to place itself on the mRNA sequence of the interested RNA ->
use some type of marker on top of complementary sequence to detect where the RNAs are
located
Gene Regulation
1. Post translation modification factors
2. Histone modification
a. Regulating promoters
b. Simply not letting a gene transcribe
3. Tissue specific transcription factors
a. Only takes effect if another molecule is present
b. Positive and negative regulation
4. Alternative splicing
5. micRNAs
a. attahes to the UTR ’ ed to ihiit the ell traslatio
DNA-> Transcription -> mRNA -> read by ribosome -> amino acid chain (protein)
Gene promoter: stretch of DNA sequence upstream to the transcription start site
Binds to basal transcription factors and RNA polymerase -> induce transcription of the gene
Futio of the ’ UTR
Proteis ad other RNAs a id to the ’ UTR
Ihiit the idig of traslatio iitiatio fators to the 5’ ed of RNA
micRNAs to cause degradation
polyA tail is needed for stability of the mRNA -> protect from random degradation
Rules of evidence
1. correlative evidence (find it)
a. establishes plausibility that particular events are involved in another event
2. loss of function evidence (lose it)
a. establishes necessity of the particular event to another
3. gain of function evidence (move it)
a. establishes sufficiency of one event to other events
forward genetic screen
purpose: identify genes that regulate specific developmental processes
method: treat to cause mutation in the DNA sequence -> cross new mutations to create
homozygous mutants and screen for abnormalities
we are creating a bunch of mutations and seeing which one causes the changes
backward would see the changes and plot out what mutations are in the changes
5 steps of sperm-egg interaction
1. chemoattraction
2. induction of acrosome reaction
3. sperm binding to egg envelop
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4. popassage of sperm through egg
envelope
5. gamete fusion
species specific peptide => allows sperm to swim
in the correct direction
zona pellucida => species specific
sperm finding the correct egg
soluable molecules secreated by the egg
guides the sperm by chemotaxis and
activates their motility
calcium level increases in the sperm tail
to swim up the concentration gradient
=> activates ATP generation
capacitation (change in sperm physiology in preparation for fertilization
membrane properties change => cholesterol removed, protein association altered
ion channels open => change cytoplasmic pH => allow Ca++ influx
cAMP produced => activate protein kinases
acrosome reaction (step 2 of the contact)
fusion of the outer acrosomal membrane with the sperm plasma membrane => releasing
proteases to digest egg coverings and expose proteins
actin is NOT pushed out for mammalian organisms
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