Fertilization (1) Flashcards
What did Antonie Philips van Leeuwenhoek do?
- invented the first microscope
- discovered animalcules (sperm) and hypothesized that they were involved in reproduction
What idea was opposing ‘sperm’?
- ovist theory
- within the egg there is a tiny complete person
- some sort of energy transfer from males to females makes the eggs grow
After sperm were discovered, what properties/details were then found?
- sperm were traced back to the testes
What is the preformationist theory? And what theory opposes it?
- that there is a homunculus or small man within the head of the sperm
- the epigenesis theory opposes this: embryo formed “from scratch” in a step wise manner
What experiment did Leewenhoek do to provide evidence that sperm are involved in reproduction? What type of experiment is this?
- first, put eggs and a male frogs together and produced offspring
- next, put male frogs with pants on with eggs and produced no offspring
- loss of function experiment
What is Occam’s razor?
- using the simplest method or simplest explanation
What is the scientific process?
- observation: question/problem
- hypothesis
- experimentation
- understanding mechanism
- repeat
What are the types of data?
- correlative
- loss of function
- gain of function
What is an assay?
- an analysis/experimental procedure that generates a specific response/read-out
What is an example of an assay?
- over-the-counter pregnancy test kit
- the assay is the immunodetection of hCG (human chorionic gonadotropin which is elevated in pregnant women)
- urine is what’s being assayed
- indicated by a blue line
What is the “technical” key to successfully carrying out one’s research?
- a great assay
- the best assays are simple, often providing a yes or no outcome
Does the blue band prove pregnancy?
- no
- the only thing the test strip says is that something in the urine is causing an immunochemical reaction to create the blue line
- this can only “suggest” that the person is pregnant
- there are alternative explanations or caveats
What are some alternative explanations to a negative pregnancy test?
- not peeing on the stick
What is a control that can be used for pregnancy assays?
- a control band that appears when the strip is wetted
- this is a positive control
What are controls?What types of controls are there?
- measures put in place in an experiment to demonstrate the veracity of your data
- positive and negative
- a good experiment will have both
What experiment did Spallanzani do after the pants experiment?
- he diluted the semen (and made the assumption that there was no sperm) and added eggs
- he got tadpoles
- this caused the ovist preformation theory to regain favor
What did Fol and Hertwig do? What did this do?
- observed sperm-egg interaction in echinoderms (correlative data)
- Hermann Fol: starfish
- Oscar Hertwig: sea urchin
- ended the preformationist theory
- power of correlative data
What is the model organism Strongylcentrus purpuratus?
- sea urchin
- closer to vertebrates than other invertebrates like arthropods
- basal deuterostomes provides an out-group for the chordates and thus insights into vertebrate evolution
- majority of genes have vertebrate orthologues
What are some general reasons for choosing a model organism?
- similarity to humans (in this course developmentally)
- practical reasons: easy to acquire and raise
What are the three sections of the sperm?
- head
- mid piece
- tail
What does the head of the sperm contain?
- acrosome (outer layer)
- plasma membrane
- nucleus
What does the mid piece of the sperm contain?
- “motor”
- centriole (microtubule organizing centre) (near head)
- mitochondria (along the outer edge)
What does the tail of the sperm contain?
- terminal disc (where midpiece and tail meet)
- axial filament (aka axoneme)
What is the basic structure of flagella and cilia?
- there is a basal body that is structurally identical to centriole
- there are 9 outer microtubule doublets and two central microtubules
- mt’s tethered to dynein
