Fertilization (1)

Question 1

What did Antonie Philips van Leeuwenhoek do?

Answer 1

• invented the first microscope

- discovered animalcules (sperm) and hypothesized that they were involved in reproduction

Question 2

What idea was opposing ‘sperm’?

Answer 2

• ovist theory
• within the egg there is a tiny complete person
• some sort of energy transfer from males to females makes the eggs grow

Question 3

After sperm were discovered, what properties/details were then found?

Answer 3

• sperm were traced back to the testes

Question 4

What is the preformationist theory? And what theory opposes it?

Answer 4

• 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

Question 5

What experiment did Leewenhoek do to provide evidence that sperm are involved in reproduction? What type of experiment is this?

Answer 5

• 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

Question 6

What is Occam’s razor?

Answer 6

• using the simplest method or simplest explanation

Question 7

What is the scientific process?

Answer 7

• observation: question/problem
• hypothesis
• experimentation
• understanding mechanism
• repeat

Question 8

What are the types of data?

Answer 8

• correlative
• loss of function
• gain of function

Question 9

What is an assay?

Answer 9

• an analysis/experimental procedure that generates a specific response/read-out

Question 10

What is an example of an assay?

Answer 10

• 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

Question 11

What is the “technical” key to successfully carrying out one’s research?

Answer 11

• a great assay

- the best assays are simple, often providing a yes or no outcome

Question 12

Does the blue band prove pregnancy?

Answer 12

• 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

Question 13

What are some alternative explanations to a negative pregnancy test?

Answer 13

• not peeing on the stick

Question 14

What is a control that can be used for pregnancy assays?

Answer 14

• a control band that appears when the strip is wetted

- this is a positive control

Question 15

What are controls?What types of controls are there?

Answer 15

• measures put in place in an experiment to demonstrate the veracity of your data
• positive and negative
• a good experiment will have both

Question 16

What experiment did Spallanzani do after the pants experiment?

Answer 16

• 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

Question 17

What did Fol and Hertwig do? What did this do?

Answer 17

• observed sperm-egg interaction in echinoderms (correlative data)
• Hermann Fol: starfish
• Oscar Hertwig: sea urchin
• ended the preformationist theory
• power of correlative data

Question 18

What is the model organism Strongylcentrus purpuratus?

Answer 18

• 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

Question 19

What are some general reasons for choosing a model organism?

Answer 19

• similarity to humans (in this course developmentally)

- practical reasons: easy to acquire and raise

Question 20

What are the three sections of the sperm?

Answer 20

• head
• mid piece
• tail

Question 21

What does the head of the sperm contain?

Answer 21

• acrosome (outer layer)
• plasma membrane
• nucleus

Question 22

What does the mid piece of the sperm contain?

Answer 22

• “motor”
• centriole (microtubule organizing centre) (near head)
• mitochondria (along the outer edge)

Question 23

What does the tail of the sperm contain?

Answer 23

• terminal disc (where midpiece and tail meet)

- axial filament (aka axoneme)

Question 24

What is the basic structure of flagella and cilia?

Answer 24

• 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

Question 25

What generates the driving force of sperm?

Answer 25

- dynein ATPase generates the force driving flagellar motility

Question 26

How do flagellum vs cilia move?

Answer 26

- flagellum: have a small part of tail that is a passive part in motion (does not move), rest moves in propeller like motion - cilia: entire cilia moves in back and forth beating motion

Question 27

What are cilia useful for in the body?

Answer 27

- transport mucus by stationary ciliated cells in the trachea - photoreceptors (non-motile)

Question 28

What is Kartagener syndrome?

Answer 28

- human syndrome caused by immotile cilia | - subjects had immotile sperm and no mucociliary transport (so had frequent brochitis and sinusitis)

Question 29

What is the cause of Kartagener syndrome?

Answer 29

- electron microscopy indicated that cilia from cells of these patients lack dynein arms - using a "forwards genetics" approach found that mutations in DNAH5 cause primary ciliary dyskensia and randomization of left-right asymmetry

Question 30

What is Kartagener syndrome also known as?

Answer 30

- primary ciliary dyskinesia

Question 31

What is DNAH5?

Answer 31

- dynein heavy chain 5 | - 79 exons

Question 32

What mutations were found in DNAH5?

Answer 32

- 10 mutations were identified in 8 families - many resulted in "nonsense" mutations - slide 58?

Question 33

How does the sperm find the egg? How was this study conducted?

Answer 33

- could be chemoattractant - applied one nanolitre of purified sea urchin egg jelly extract to dish containing sperm - sperm surrounded the jelly increasing with time