Unit 2 Flashcards
What is meiosis one?
- divides nucleus
- aka karyokinesis
What are the phases of meiosis one?
interphase
early prophase
mid prophase 1
late prophase 1
metaphase 1
anaphase 1
telophase 1
What happens in interphase?
- no cell division just DNA replication
What happens during metaphase one?
chromosomes at metaphase plate
What happens at telophase 1?
reduction of gene complexity complete
What are the phases of meiosis 2?
metaphase 2
anaphase 2
telophase 2
What is the difference between mitosis and meiosis?
- meiosis =4 unidentical gamete haploids
- mitosis = 2 identical diploid daughter cells
What happens in oogenesis?
- one egg and formation of polar bodies
- polar bodies degrade and get recycled
What is the cycle of an egg?
- germ cell
- oogonium
- meiosis 1
pauses in prophase 1 during late diplotene and becomes a dictyate stage - primary oocyte
- resumption of meiosis at puberty
- secondary oocyte and first polar body
meiosis pauses at metaphase 2 - fertilization resumes meiosis
- ootide
- ovum where polar bodies degrade
What does straw 8 do in female meiosis?
- allows germ cell to enter meiosis
- Retinoic acid to stra8 to meiosis
What does stra8 do in males?
- retenoic acid inhibited by cyp instead of going to straw 8
- also inhibited by nanos to stop meiosis
- stra 8 is inhbited by cyp26b1 in males, if no cypb nanos 2 inhibits stra8
What happens if there is cyb26b1 in females?
- turn into males during meiosis
- diet to vitamin a
- adh
- retinal to raidh
- retinoic acid
- cypb261
- oxidized A
What happens during ovulation?
- forms corpus lutea
- egg is in graafian follicle with a small amount of cells surrounding it
- thecal cells can secrete androgen hormone
- granulosa cell secrete aromatase enzyme
- aromatase takes testosterone and makes estradiol
what is the ovulatory cycle?
- gnrh to fsh to lh to uterine cycle or ovulation
- ovulation to corpa lutea to estradiol to inhibition to progesterone
What is the male cycle?
- gnrh to fsh to lh to spermatogenesis
- much faster cycle
- all four germ cells maintained during spermatogenesis
- no complete karyokenesis and cytoplasmic bridges
- not really polar bodies
- must self renew
- lots of different types of spermatogonia stem cells
How many types of spermatonial stem cells are there?
lots
What is sperm flagellum?
microtubial based
motile
basal dependent
What do acrosomes do?
- golgi derivatives that breaks down the cells surrounding the egg
Where do cumulus cells come from?
granulosa cells
What are environmental queues in aquatic organisms?
temp and current
What does sperm egg binding cause?
Ca2+ goes in and triggers sperm to go to the peptide and egg
What is the receptor in sea urchin fertilizaiton?
- Receptor guanine cyclase
- binds to Calcium receptor in sperm
What does the acrosome do when it binds?
- activates it, releases enzyes to break down the jelly layer of egg and exposing bindin receptor
- bindin then binds and sperm and egg undergo fusion
What are the problems with fusion?
- has to overcome thermodynamic problems
- sea urchins have gactin that goes to f- actin
How does the egg cause acrosomal species specific reactions?
- jelly coat is species specific
How do sea urchins avoid multi-sperm fertilization?
- embryo will die because chromosomes don’t know where to go
- salt comes in and changes egg membrane and stops multi-binding
- doesn’t happen in internal fertilizers because no species specification is needed
What is a slow block to polyspermy?
- fertilization envelope forms around egg and blocks it from more sperm
- unfertilized egg has villi covering membrane bound organelles and cortical granules below plasma membrane
- once spem binds the villi dissolves and the cgst creates h202 creating ovop and creatig hardening of fertilization envelope
How does the ER block multi-fertilization?
- ER with Ca2+ surrounds egg, when sperm binds and envelope expands, Ca2+ releases over egg and activates egg
- sperm then activates PLC which then activates Pip2 and cleaves to Dag releasing IP3 which releases more Ca2+
- Ca2+ activates egg, speeds up fertilization envelope formation activates Na+ H+ gates
What are the steps to mammilian fertilization?
- capacitation leading to the hyperactivation of ferm
- sperm senses and follows progesterone gradients
- undergos acrosome reaction
- fuse with egg plasma membrane
What happens when the egg undergoes the acrosome reaction?
- zona pellicula mediated event
- zona pellicula has three zones and the glycoproteins help with this
- protiolytic enzymes break down egg barrier
How does the sperm fuse with the egg plasma membrane?
- izumo and juno lower themodynamic barriers and content mixing
- the male mitochondria is destroyed and ovastacin protease found in ocrtical granules
What are izumo and juno?
- izumo is on sperm and juno is the receptor on egg
What is the zinc spark?
- lasts less than 40 seconds
- blocks acrosomal enzymes
How do sea urchins have 5 fold symmetry?
- because of holoblastic and radial cleavage
- 2 meridional and then equatorial so 3 total symmetry axis
Are sea urchins chemically equal?
- biochemically unequal but same genetic info
- there is originally no zygotic info so everything is determined by mom
What does meiosis create in sea urchins?
- vegital poles create macromere and micromere
- creates cells with unique cell info
- by the end of there is only 1 axis of symmetry and equivalent info in further divisions
What is the archaenteron?
primitive stomach
What is a blastocoel?
- hollow ball that helps form germ layers and organs
- present in deuterostomes
What is a pleuteus?
- sea urchin larvae
How are sea urchins divided?
- animal 1/2 of equatorial creates dorsal blastula
- vegetal 1/2 creates embryo that couldn’t move or form body
What is in the vegital half of a sea urchin?
- creates embryo that couldn’t move or form body
- has maternal determinant: disshevled leading to beta catenin
What does disheveled do in sea urchins?
- in vegetal half
- blocks destruction complex to save beta catenin
- disheveled blocks gsk3 which blocks beta catenin
What does licl do?
- blocks gsk3 which blocks beta catenin
- more licl= more beta catenin
What does beta catenin do?
- helps form adherens junction but is localized to vegital pole in micromeres and veg 2 cells
What are micromere?
- cell autonomous
What is ingression?
- an epithelial to mesenchymal transition
- happens to a cell as they respond to signals
- micromeres become primary mesenchymal cells
What does CSPG cause?
- water absorption and expansions of lamina to push cells to blastocoel
What is a proteoglycan?
protein core with millions of sugars
What is a hydroscopic cell?
- love to bind water
What do PMCS do?
- go to regions of FGF expression since micromeres have FGF receptors that cause outlining of cells
- PMCs express B-cat and down regulate it so its no longer in the PMCs
- PMCs then form syncytium which allows the to create their skeleton
What is the first example of gastrulation?
- PMCs forming syncytium which allows them to create their ckeleton
What does gastrulation do?
- invagination
- cell shape changes/ rearrangements
- filopodial extensions
- convergent extension
How do archenteron form?
- goes through convergent extensions to form tube like elongation
- lamellipodia and filipodia are found in mesenchymal cells and localize towards direction of movement
What does the amniote egg for?
- for things that aren’t 100% in water
- allows gas exchange without dehydration
What does frog sperm contribute?
- centriole
Where does fertilization occur?
- animal hemisphere
What does fertilization do?
- specified dorsal-ventral axis
- initiates cortical rotation by microtubules
- specifies that gastrulation will occur on dorsal side
What happens during cortical rotation?
- reorganization of cytoskeleton
- dyenin goes towards negative end from centriole
- kinesin goes towards positive end from centriole
- vegital 1/2 kinesin gives illusion of movement
- kinesin uses ATP to generate force and they are carbocarriers
What is the goal of cortical rotation?
- accumulate beta cat next to dorsal pole
- create first cleavage plane
Where does gastrulation occur?
- in grey crescent
What do dissheveled and beta cat do?
- allow activation of gene transcription with WNT
- WNT in sea urchins forms micromeres and autonomous specification
- WNT in frog creates dorsal ventral polarity
What do disshevled and GBP do in grogs?
- prevent beta catenin degradation in vegetal area
How does cleavage occur in frogs?
- homoblastic complete cleavage radially displaced towards animal pole
- animal is cleaved before vegetal
- vegital pole is denser
- 1st equatorial cleaveage 3 occurs before 2 meridional cleavages 1+2
Describe early cleavage?
- reductive and fast
What is cdk1 used for?
- phosphorylation
What is weel for?
to turn off phosphorylation
What is cdc25a used for?
- maternally deposited to tell cell how to cleave
- goes s to m for the first few cycles
What is a blastocoel filled with?
- water and lots of protein
- bottle cells form within
- constricts on 1 side not the other, starts invagination and goes into blastocoel
What do alpha tubules do?
- organize microtubules on corticle area ( cell edge)
- bottle becomes archaeon
What is the bottle?
- becomes archaeon
- actin and myosin contract and form rossets
- forms dorsal blastopore lip where b cat used to be allows for the formation of 3 germ layers
What happens if beta catenin is at the dorsal end?
- transplanted to the other side and another lip forms
- like a mirror image
- proved by conditional cells in the spman hilde experiment
What is the dorsal lip?
- organizer and a primary induction event helped by the nicoup center
- initiates gastrulation
- specifies dorsal mesoderm from prechordal plate and chorda mesoderm
- dorsalizes ectoderm to aquire neural fate
- dorsalizes adjacent mesoderm and paraxial mesoderm instead of ventral mesoderm
- specificies pharyngeal endoderm
How does the lip effect surrounding tissues?
- releases morphogens
- time carefully, need to preform translocation before cell is specified
- once cells start talking to eachother their fate is determined
What is a psuedogene?
- mutations making protein inactive
- 1 protein to 1 fully working protein and 1 inactive protein
What is a subfunctioning protien?
- goes from 1 fully functioning protein to 2 1/2 functioning proteins
What is neofunctionalization?
- creates a protein with a totally new function
What are the ways proteins can be replicated?
- neofunctionalization
- subfunctions
- psuedogenes
How do two of the same thing form?
- beta catenin is orgalization and beta catenin stabelization causes TF cascade
- utilizes chordin, noggin, goosecoid, cerebrus, siamus, xenopus
- heavy emphasis on veg T and Vg1
What do veg t and vg1 do?
- beta catenin can’t work alone to specify organizer
- veg t is the transcription factor and vg 1 is the ligand
- activates smad phosphorylation allowing for smad to enter nucleus due to the phosphorylated AA changing folding
- when smad enters nucelus it starts transcripiton
What does vegT do without b-cat?
- prevents formation of organizer on presumptive ventral side
What happens when b-catenin is low?
- different mesoderm formations
What is special about the endoderm?
- it has inductive properties to make cells in marginal zone form mesoderm
If you slice an egg will it create 2 functioning offspring?
- depends on where you slice it
What does the ectoderm form?
- nervous system
What does the endoderm form?
pharynx
What does the anterior mesoderm form?
- head muscle and bone
What does the posterior mesoderm form?
- nodalchord
How is the brain formed?
- no wnt
- no BMP
- chordin
- noggin
- cerebrus
How is the spinal chord formed
- WNT
- Noggin
- chordin
- no BMP
- NO cerebrus
How is the majority of the embryo formed?
- WNT
- BMP
- No chordin
- no noggin
- no cerebrum
What does cerebrus do?
- inhiits wnt which kinda leads to BMP
What does chordin and noggin do?
- inhibits BMP
What is sox 2 good for?
- neural formation
What happens if chordin and noggin are knocked down by morpholino?
- no neural markers
What is morpholino?
- DNA backbone that can’t be cleaved
What happens when BMP is knocked down by mopholino?
- no midline
- sox-2 is everywhere
- anti-dorsalizing meaning sox 2 gets into ventral 1/2
