module 11 Flashcards
question: how is apoptosis a part of sculpting digits?
- week 6 of dev. = skin webbing between digits
- week 11 = webbing gone
- skin is gone bc apoptosis
question: what does a TUNEL assay do?
- see nicks/DNA breaks in DNA
- dUTP is incorporated into nicks by adding enz.
⤷ deoxynucleotidyl transferase
question: how is apoptosis involved w/ frogs?
- tadpole goes through metamorphosis to become frog
- apoptosis removes tadpole tail
- apop. stim. by thyroid hormone in blood
**similar tail loss happens in humans
question: how is apoptosis involved in nervous system?
- normal brain only needs 1/2 of the neurons originally produced
- cells that don’t achieve synaptic connections get cell death
question: how can cell death be bad in the human body? (4 ex.)
- inappropriate cell death -> disease
- ex. alzheimer’s
⤷ neurons in hippocampus region die - ex. huntington’s
⤷ neurons in striatum die - ex. parkinson’s
⤷ dopamine neurons in substantia nigra die - ex. duchenne muscular dystrophy
⤷ muscle cells atrophy
question: what are the ways in which a cell can die? (2) + define them
- necrosis
⤷ cells swell and release contects into surrounding tissues
⤷ bad (can lead to infection) - apoptosis
⤷ disposal of cellular debris that doesn’t damage surrounding cells
⤷ from stress, damage, or normal development
question: what are the steps of the apoptotic pathway? (3)
- execution
- engulfment
- clearance
explain: process of apoptosis
- chromatin condenses
- nuclear envelope breaks down
- nucleus contents = fragmented
- DNA broken down
- cell mem. blebs
- makes compartments each filled w/ debris from dead cell
- each fragment gets phagocytized
⤷ reused and recycled
question: what is blebbing?
- creating protrusions or bulges as the cell shrinks
- happens to cell mem.
question: why c.elegans good for apoptosis studies?
- know there are 947 somatic cells
- can tell that exactly 131 cells undergo apoptosis
question: how were c.elegans studied for apoptosis?
- used assay to ID muts. in genes required for apop.
⤷ cell death genes = ceds
question: what is the effect of ced-1 on cell death in c.elegans
- loss of func. mut. in ced-1 leads to apop. but cells not engulfed by phagocytosis
⤷ so they stay and researchers can study
question: is ced-3 important in apop.? what if there’s a mut. in ced-3?
- mut. in ced-3 -> no apoptotic genes
- if ced-3 not functional, no apotosis can take place
name: genes required for apop. in c.elegans?
- ced-3
- ced-4
- ced-9
- egl-1
question: what is the human homologue for the c.elegans genes?
- ced-3 = caspase-9
- ced-4 = apaf-1
- ced-9 = Bcl-2
- egl-1 = Bid, Bim, Bad
⤷ Bid reg. Bak
⤷ Bim reg. Bax
question: what does each gene do in c.elegans apoptotic pathway?
- ced-3 and ced-4 form complex = caspase holoenz.
⤷ targets diff. prot. for degradation - ced-9
⤷ inhibitor of apop.
⤷ inhibit activation of the caspase holoenz. - EGL-1
⤷ sig. for apop. that activates pathway
⤷ inhibits ced-9
explain: results if caspase holoenz. or ced-9 had a mutation
- ced-3 ced-4 complex
⤷ no apop. - ced-9
⤷ all cells die
question: what does the caspase holoenz. do?
- protease activity
- prot. degradation
- cell death
question: how is the caspase holoenz. activated (formed)?
- ced-9 is inhibiting by binding to ced-4 dimers
- adding egl-1 inhibits ced-9 to release ced-4
- ced-4 binds to 3 and forms caspase holoenz.
- formation -> activation
question: what is the role of mito. in apop.?
- ced-9 prot. (Bcl-2) is on surface of mito.
- prot. on mito mem. changes it’s permeability
question: what do Bad and Bax do (cytochrome C)?
- apoptotic sig. = Bad
- Bad = inactive until dephosphorylated
- Bad binds to Bcl-2 -> activation of Bax (another ced-9 prot.)
- Bax aggregates and forms pores that increase permeability and release mito. into cytosol
- also releases cytochrome C
question: how does trophic factor removal lead to apop.?
- trophic factors prevent apop. (initiate kinase cascade to phosphorylate Bad)
- removing trophic factors -> Bad can be dephosphorylated -> apop.
