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Biology 102 class sets > Fertlization > Flashcards

Fertlization Flashcards

1
Q

What is fertlization

A

It’s the joining of a haploid sperm and egg to form a diploid zygote

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2
Q

What are the problems that the sperm has to solve before fertilizing the egg?

A

-1. Find a conspecific egg
- 2. Move the sperm pronucleus into the egg cytosplasm

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3
Q

What are the problems that the egg has to solve for fertilization to be successful?

A
  • attract conspecific sperm
  • avoid polyspermy ( allow only one sperm to insert its pronucleus into the egg)
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4
Q

How can cross-fertilization be reduced?

A
  • having specific timing which is gamete release controlled by water temperature or by the phase of the moon.
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5
Q

What are the four species recognition mechanisms at the molecular level?

A
  • sperm attraction to an egg
  • sperm activation
  • digestion of egg jelly
  • sperm ahesion to the egg surface
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6
Q

The four mechanisms are

A

four different opportunities for species specificity.

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7
Q

What is CHEMOTAXIS ( sperm attraction to the egg chemotaxis )

A

It’s the directed cell movement up a concentration gradient.

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8
Q

What are the 4 steps of chemotaxis

A
  • egg releases a factor
  • sperm has a receptor
  • receptor/ ligand interaction affects flagellar motion
  • sperm swim towards the highest concentration of the factor.
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9
Q

The mechanisms of chemotaxis may differ among species

A
  • True
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10
Q

Some of the chemicals used for chemotaxis are related.

A

-and sperm of different species may find the egg because of high concentration may cause their attraction.

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11
Q

2nd step in cell recognition What happens when the sperm contacts the egg Jelly

A

The acrosomal vesicle gets triggered

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12
Q

What does it mean for the acrosomal vesicle to be triggered

A

It means the acrosomal vesicle within the cell fuses with the plasma membrane of the sperm and releases its proteins to the outside.

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13
Q

The process by which the vesicle releases its substance to the outside world is called

A

exocytosis

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14
Q

What do the proteins that get released from the acrosomal vesicle do?

A
  • They can be enzymatic digestion of jelly coat but can also be a chaperone like proteins that unwind the jelly coat
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15
Q

What is unique about the glycoproteins within the vitelline envelope and jelly coat

A
  • It may vary between species to species so the contents of the acrosome need to be specific to the task of making path through the vitelline envelope.
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16
Q

The third step of cell recognition occurs when the Acrosomal process encounters the vitelline envelope and adheres in a species-specific way.

A

The acrosomal process encounters the vitelline envelope and adheres in a species-specific way.

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17
Q

Bindin

A
  • It mediates recognition, and the species-specific acrosomal protein binds to the receptor on the egg.
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18
Q

What does the 4th step, which is the plasma membrane contact,t do

A
  • triggers a cascade of events known as egg activation.
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19
Q

Gamete fusion

A
  • ## The nucleus of the sperm enters the egg, and the fertilization cone is formed.
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20
Q

What is fertilization cone

A
  • a mound of cytoplasm that surrounds the sperm nucleus.
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21
Q

All of the mechanisms are probably evolved by selection to avoid

A

wasting large expensive eggs by having them fertilized by the wrong species sperm.

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22
Q

Fertilization is unlikely when

A
  • there are relatively few sperm present
  • also unlikely when there are many sperm present.
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23
Q

Why does the fertilization egg development curve go down when there are lots of males and lots of sperm?

A
  • Eggs fertilized by more than one sperm do not develop
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24
Q

There is a strong selective pressure

A
  • to ensure that exactly one sperm fertilizes the egg.
25
What is monospermy
Only one sperm enters the egg, and a haploid egg nucleus and haploid sperm nucleus combine to form a diploid nucleus of the cell that is now a zygote.
26
What is polyspermy?
The entrance of multiple sperm ( very disastrous in most organisms)
27
What are the primary mechanisms that prevent polyspermy?
1, Triggered by the first successful sperm and 2. Fast in case there happen to be thousands of sperm near an egg 3. Must be permanent.
28
What is fast block
As its name implies, it occurs very quickly. It's initiated within seconds, lasts only about a minute, and's achieved by a change in the electrical potential of the egg cell membrane
29
How does the fast block work
For the egg and for just about any living cell, the resting membrane potential is about -70mv. Within one second after the binding of the first sperm, the membrane potential shifts to about +20.
30
The slow block to polyspermy - the cortical reaction ( zona reaction in mammals)
-When a sperm successfully fuses with the egg membrane, it triggers a wave of calcium ions (Ca²⁺) inside the egg. -The calcium wave causes cortical granules (small vesicles under the egg membrane) to release their contents into the space between the egg membrane and the surrounding vitelline layer (or zona pellucida in mammals). - The enzymes from the cortical granules modify the proteins in the vitelline layer (or zona pellucida in mammals), making it harder and preventing more sperm from binding
31
How do you get from one cell to a multicellular organism
MITOSIS!
32
What happens during mitosis
One parent cell gives rise to two genetically identical daughter cells
33
What are the 2 problems that the cell has to solve during mitosis
- Avoid tangling - how do the sister chromatids pair up - how to get one sister chromatic from each chromosome to the opposite ends of the cell
34
How does the DNA avoid tangling
- by being packaged into a condensed form
35
Each daughter cell needs to get exactly one copy of each sister chromatid
- so the matching chromatids pair up, line up, then split apart, and move to the end of the cell. then the cell needs to be split into two
36
How does one get one sister chromatid from each chromosome to the opposite ends of the cell?
The cytoskeleton plays a major role
37
What are the three components of cytoskeleton
- microtubles - microfilaments - intermdediate fillaments
38
What are microtubles
they are dynamic and constantly growing and shrinking adding building blocks at one end( the plus end and removing them at the other end
39
polymerization vs depolirization
is the adding of subunits of microtubles and removing
40
What happens at the beginning of mitosis
- the microtibles reconfigure to form a spindle, which is a star like arrangement, each anchored by centrosomes and extending towards the center
41
What is kinetochore
It's a protein complex that binds to the DNA that forms the centromere. At the centromere, there are as many kinetochores as there are chromatids, so there are 2. Each kinetochore includes a binding site for the + ends of microtubules.
42
What are the three kinds of microtubles
- Astral - spindle - Kinetochoer - they all different functions based on which direction they point on where they point and where they touch
43
What are microtubles made up of
alpha and Beta tublins when the two join together it's called a dimer Dimers will form long chains of polymers
44
Microtubles
are dynamic they grow and shink really fast
45
what is MTOC
one side of the microtubles
46
how do kinetochores bind to a microtuble
In a random manner to any microtuble they encounter. They also release it unless microtuble junction is under tension.
47
when is there tension
- when the two kinetochores from two sisterchromatids are bound to the opposite centrosomes - if the two kinetochores are bound to opposite end tension builds up trying to pull the chromatids apart locking the microtibles onto the kinetochores. since the sisterchromatids are locked in with coheision
48
what happens when all Kinetochores are under tension
The APC (anaphase promoting complex) is activated and it proceeds to tag a protein securin for degradation and so releases separase which cleaces cohesions and then boom the microtubles bound to kinetochores pull the sister chromatid to the opposite poles.
49
How about cytokinesis?
In anaimals the cell is actually pinched off by actin and myosin
50
What are the steps in meiosis
- chromosomes bundles up by cohesion , centrosomes one per chromosme bind to kinetochores - microtubles grow out from centrosomes and bind to kinetochores if bound to opposite poles tension results. MItosis doesnt start until all kinetochores are under tension.
51
what is Assexual reproduction
it's when organisms use mitosis to reproduce by which the production of offspring whose genes all come from a single parent. i.e Acorn worms
52
Acorn worms
uses Frangmentation a type of sexual reproduction wheret the parent breaks into parts that regenrate into new individuals.
53
annelid worms
use either fragmentation or budding which is a type asexual reproduction in which outgrowths from the parent form and pinch off to live indepedndetlt or else to ewmin attached eventually form extensive colonies.
54
what makes mitosis and checkpoint unique
The process is well conserved evolutionarily ensuring that daughter cells have identical chromosomal complements.
55
What makes meiosis unique?
it most likely evolved from mitosis has some weirdeness to it.
56
What is the difference between meiosis and mitosis
-in meiosis 1. crossing over happen results in recombination of genetic material -separation at anaphase is not of sister chromatids but of paired chromosomes
57
What are the outcomes of meiosis
-crossing over by recombination. - independent assortment - Fertlization - combining with another individual
58
how long does recognition sequence.
it relies on chromosomes randomly moving and meeting matching recongonotion sequence which ususlaly takes 24 days
59
What is Gametogenesis

Biology 102 class sets (5 decks)

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