FERTILIZATION Flashcards
____ Beginning of a New Organism
is the process where male and female gametes (sperm and egg) unite, typically occurring in the _____, which initiates the development of a new organism.
Purpose:
perpetuation of species through sexual reproduction.
determines the sex of the organism
Functions:
Transmit genes from parent to offspring
provides for recombination of paternal and maternal genes.
restoring the diploid chromosome number and ensuring genetic diversity.
Activates the egg to begin development
Fertilization
Uterine tube
Main Events During Fertilization:
- _____ between sperm and egg.
- Regulation of _____ into the egg.
- Fusion of ____
- Activation of ____ to start development.
Main Events During Fertilization:
Contact and recognition
sperm entry
Genetic Material
egg metabolism
STRUCTURE OF THE GAMETES: SPERM
____has hydrolytic enzymes for penetrating the egg
Cell body:
Contains _____
Neck:
_____
Tail:
_____ - core structure and contains: _____
______ ATPase causing flagellar bending
Acrosome
Cell body:
Pronucleus
Neck:
ATP/Mitochondria
Tail:
Axoneme contains: Tubulin
Dynein
Sperm parts (4)
Crucial part for the tail _____
Sperm parts (4)
acrosome
nucleus
mitochondria
tails
Axial filaments
The golgi apparatus forms the ______, which contains enzymes important for fertilization.
The ____ begin to migrate to one end of the cell, initiating flagellum formation.
acrosomal vesicle
centriole
Diagnosis of Kartagener’s syndrome:
Triad of symptoms (Characterics of KS 3):
Bronchiectasis
Chronic Sinusitis
Situs Inversus Totalis
Diagnosis of Kartagener’s syndrome:
_____ supports the diagnosis of Kartagener’s syndrome.
Moderate ____
Respiratory Failure Type 1 (Hypoxia without hypercapnia)
have a 50% chance that the heart is located on the ____ side of the body because of immotile cilia
Infertility
Airway Obstruction
right
Diagnosis of Kartagener’s syndrome:
Kartagener’s syndrome is a subset of ______ , a genetic disorder that affects the cilia. Because the cilia are immotile, they cannot perform their usual functions, leading to respiratory issues (due to mucus buildup in the lungs), chronic sinus infections, and issues with organ positioning (situs inversus).
Primary ciliary dyskinesia (PCD)
STRUCTURE OF THE GAMETES: EGG
All material necessary for the beginning of growth and development must be stored in the egg:
- _____ - like yolk (made in other organs; mostly liver)
- _____ burst of protein synthesis after fertilization
- _____ encodes proteins for use in the early stages of development.
Messages remain repressed until after fertilization - _____ direct the differentiation of cells into certain type
- Types of Protective chemicals (3)
STRUCTURE OF THE GAMETES: EGG
1. Nutritive proteins
- Ribosomes and tRNA
- mRNA
- Morphogenic factors
transcription factors, and paracrine factors - UV filters
DNA repair enzymes
Antibodies
Sea Urchin Egg:
- _____
Analogous to the mammalian zona pellucida, this is an extracellular matrix that forms a “fibrous” mat around the egg, playing a crucial role in sperm-egg recognition. - ______
Resides outside the vitelline envelope in some species; it attracts and activates sperm, aiding in the capacitation process. - _____
Located just inside the plasma membrane, these granules release enzymes that modify the vitelline envelope upon fertilization to prevent polyspermy. - _____
One sperm adheres to the egg cell membrane then the egg releases chemicals that drive the other sperms away from the egg and forms a fertilization barrier that cannot be penetrated. - _____
Provides the energy required for the egg’s metabolic activities post-fertilization.
Sea Urchin Egg:
- Vitelline envelope
- Egg Jelly
- Cortical Granules
- Plasma Membrane
- Mitochondrion
Mature (Vesicular) Follicle / Graafian Follicle:
- _____
Layers of cells that surround the follicle, playing roles in structural support and hormone production, respectively. - A fluid-filled cavity that forms within the follicle, which increases in size as the follicle matures.
- The actual gamete, arrested in metaphase of meiosis II until fertilization.
- A layer of cells that adheres to the oocyte and must be penetrated by the sperm prior to reaching the zona pellucida.
- Surround the oocyte and are involved in its nourishment and the production of sex steroids.
- A cluster of cells that anchors the oocyte to the follicle wall.
- A glycoprotein layer surrounding the oocyte, crucial for sperm binding and activation during fertilization.
Mature (Vesicular) Follicle / Graafian Follicle:
- Theca Externa and Theca Interna
- Antrum
- Secondary oocyte
- Corona radiata
- Granulosa cells
- Cumulus oophorus
- Zona pellucida
Recognition of Egg and Sperm
- _____ Sperm are attracted by soluble molecules secreted by the egg.
- _____ Of the acrosomal vesicle to release enzymes.
- _____ Of the sperm to the egg’s extracellular envelope.
- _____ Of the sperm through this envelope.
- _____Of egg and sperm cell membranes.
Recognition of Egg and Sperm
- Chemoattraction
- Exocytosis
- Binding
- Passage
- Fusion
EXTERNAL FERTILIZATION IN SEA URCHINS
Challenges:
1. How can sperm and eggs meet in such a dilute concentration?
- How can sperm be prevented from attempting to fertilize eggs of other species?
Solutions:
- Species-Specific Sperm Attraction
- Species-Specific Sperm Activation
Species-Specific Sperm Attraction:
- ______
sperm are attracted towards eggs of their species; following a gradient of chemical secreted by the egg
_____ (cnidarian)
regulates taxis (movement) and timing of sperm
chemotaxis occurs after _____
______ control the type of sperm they attract and the time at which they attract them.
1.Chemotaxis
Orthopyxis caliculata
2nd meiotic division
Oocytes
Sea Urchin:
motility acquired shortly after exposure to seawater
in testes, sperms are immotile because of low pH (pH____) by high CO2 content in the gonad
in sea water, sperm pH ~7.6 which results in activation of _____ (flagellar motor protein)
The ability to move does not provide the sperm with directions.
~7.2
dynein ATPase
Echinoderms:
Direction is guided by egg-derived peptides called ____:
sperm activation agent
sperm in sea water swim in circles
allows sperm to congregate (accumulation of sperm cells in a particular location)
_____- 14aa peptide isolated from egg jelly of Arbacia punctulata;
_____- specific for Strongylocentrotus purpuratus
Sperm-activating peptides (SAPs)
resact
speract
Model for Chemotactic peptides in Sea Urchin:
1._____ is released by the egg and diffuses through the surrounding water. Sperm cells have receptors for it on their membrane called _____.
2 .When 1.1 binds to 1.2, it activates the receptor. This activation converts _____ into_____
- The _____ acts as a secondary messenger inside the sperm cell. It opens _____ in the sperm cell membrane.
- The influx of ____ into the sperm cell increases its _____ concentration. The elevated levels stimulate the sperm to swim towards the egg.
Model for Chemotactic peptides in Sea Urchin:
- Resact
Receptor Guanylyl Cyclase (RGC). - GTP (guanosine triphosphate)
cGMP (cyclic guanosine monophosphate). - cGMP (cyclic guanosine monophosphate).
calcium (Ca²⁺) channels - Ca²⁺
intracellular
Role of Resact in Sperm Activation:
A single resact molecule can guide sperm towards the egg by creating a _____. The sperm swim up this gradient.
Resact (______) is also known as a sperm-activating peptide, enhancing sperm motility and mitochondrial respiration.
The rise in cGMP and Ca²⁺ activates mitochondrial ATP production and dynein ATPase, which is critical for flagellar movement.
Upon detecting resact, sperm from the species Arbacia are signaled where to go and are given the necessary motive force to reach the egg.
concentration gradient
(respiration activating)
Species-Specific Sperm Attraction
- The Acrosome reaction two components:
______:
Fusion of the acrosomal vesicle with the egg cell membrane
Results in release of acrosomal contents and proteolytic enzymes
Extension of the acrosomal process or ____
Exocytosis
acrosomal filament
Sea Urchin:
- ______
The egg jelly contains specific molecules that induce the acrosome reaction.
involves the fusion of the acrosome membrane with the sperm membrane, leading to exocytosis of acrosomal vesicles and the extension of the acrosomal filament.
The activation is calcium-mediated, initiated by fucose sulfate (sulfated polysaccharides) in the egg jelly.
- _____
In Strongylocentrotus purpuratus, the acrosome reaction is triggered by fucose sulfate, a repeating polymer in the egg jelly.
- Activation by egg jelly
- Acrosome Reaction Initiation
Jelly layer: fucos sulfate rich polysaccharide
- Contact with egg jelly leads to _____which creates an influx of ____
- Diverges to:
2.1 Efflux of ____ and Influx of ____ causing intracellular increase in ____
2.2 ____ of ____ leading to release of ___ and exposure of ____
3.1 _____ leads to ____
3.2 ____ leads to increased ____
- Na depolarization
Ca 2+
2.1 Efflux of H+ and influx of Na+ causing intracellular increase in pH
2.2 Exocytosis of acrosomal vesicle leading to release of lytic enzymes and exposure of bindins
3.1 Actin polymerization leads to extension of acrosomal process
3.2 Activation of dynein ATPase leads to increased sperm motility
Acrosome reaction stages:
A. The sperm’s acrosome membrane contains ____and ____.
B. The acrosome membrane begins to break down, and globular actin starts to polymerize.
C. Acrosomal enzymes are released to digest the ____
D. The actin filaments _____, forming a process that allows bindin to interact with receptors on the egg’s _____.
A. bindin
globular actin
C. egg jelly coat.
D. polymerize
vitelline envelope
Species-Specific Recognition:
The first species-specific recognition event occurs when the sperm contacts the egg’s _____.
The ____ acts as a barrier to interspecific fertilizations, ensuring that only sperm from the same species can fertilize the egg.
jelly coat
acrosome reaction
Species-specific binding event
_____:
Specific binding proteins that mediate attachment between sperm and egg vitelline membrane
____ in Sea Urchin
a gamete recognition protein involved in speciation
adhesive protein that binds sperm to the egg surface. Without this, fertilization does not occur.
Rapid change of bindin proteins creates barriers to fertilization between species.
Acrosomal vesicle
Bindin
SEA URCHIN ASSETS:
Egg:
Vitelline membrane has receptor called ____ which is ligand specific
______ chemoattractant released by egg in water
Sperm:
Acrosome has _____ which is going to act as a ligand for EBR1.
Fertilization is species specific and occur in water.
EBR1
Resact protein
bindin protein
TRUE OR FALSE:
Sperm binding does not occur over the entire egg surface. There is a limited number of sperm-binding sites.
species-specific recognition of sea urchin gametes occurs at the levels of sperm attraction
Actin protein on acrosome sperm
EBR1 receptor on the egg jelly of egg.
TRUE
FALSE
sperm attraction, sperm activation, and sperm adhesion to the egg surface.
FALSE
Bindin
FALSE
NOT Egg jelly ITS IN vitelline membrane
_____ - only one egg enters the sperm
_____ - the entrance of multiple sperm
Monospermy
Polyspermy
Which African-American embryologist discovered the two blocks?
Ernest Everett
Blocks to polyspermy:
Fast block:
immediately causes the egg membrane resting potential rise
(1-3 sec) ____ of the egg membrane; only membranes with ____ resting potential can fuse with sperm
depolarization
-70m
Blocks to polyspermy:
slow block:
slower and caused by the ____ of the ____
becomes active about a minute after the first successful fusion
When sperm enters the cytoplasm, Answer 2 (15,000) release the following substances (4)
exocytosis
cortical granules
Protease
Mucopolysaccharides
Peroxidase enzymes
Hyaline
INTERNAL FERTILIZATION IN MAMMALS CHALLENGES:
- Fertilization happens inside the ____ of the female.
- The sperm population ejaculated into the female is very ____, with spermatozoa at various maturation stages.
- Out of approximately ____ sperm in a typical human ejaculate, only about ____ reach the egg.
- It is difficult to assay the molecules necessary for sperm to reach the egg.
- oviducts
- heterogeneous
- 280 million, 200
The translocation of the sperm from the vagina to the oviduct involves several processes that work at different times and places (3)
- Sperm Motility
- Uterine Mucle contractions
- Sperm rheotaxis: form of taxis seen in many
aquatic organisms like fish, whereby they will
(generally) turn to face into an oncoming
current.
Sperm Motility Generalizations:
_____ are critical in getting sperm to oviduct.
The _____ just before the ampulla may slow sperm down and release them over time.
Once in the oviduct, sperm exhibit increased motility (hyperactivity) near the ____.
Sperm may receive directional cues from ____ between the regions of the oviduct and ____ derived from the oocyte or cumulus.
______ must be completed during transport from vagina to oviduct
Uterine muscle contractions
oviduct region
oocyte
temperature gradients
chemical cues
Sperm maturation
A process involving physiological changes that sperm undergo after ejaculation to become capable of fertilizing the egg.
Occurs in the female reproductive tract via uterine muscle contraction
Capacitation requirements vary by species.
Sperm Capacitation
Nearly all human pregnancies result from intercourse during a 6-day period ending on the day of ovulation.
Fertilizing sperm can take up to ____ to reach the ____.
Capacitation is a transient event; sperm can become incapacitated after a period.
Sperm survival rates vary depending on their location within the reproductive tract.
6 days
ampulla
MOLECULAR EVENTS OF CAPACITATION
Lipid Changes:
Sperm cell membrane altered by the removal of cholesterol
____ in female reproductive tract remove cholesterol
Protein Changes:
Proteins and carbohydrates on surface are lost during capacitation
may block recognition sites for zona-binding proteins
____ may be an effect of cholesterol depletion
Albumins
unmasking
Hyperactivation:
Sperm of certain mammals become hyperactivated as they move from the uterus to the ____.
This hyperactivation is accompanied by the enzyme ____ on the sperm cell membrane, which helps the sperm digest a path through the extracellular matrix of the cumulus cells surrounding the oocyte.
oviduct
hyaluronidase
Thermotaxis:
Sperm can sense a thermal gradient of about ___between the ____ of the oviduct and the warmer _____
Only capacitated sperm are able to respond to this thermal gradient and move towards the warmer region where the oocyte is located.
2°C
isthmus
ampullary region
Chemotaxis:
The oocyte and surrounding ____ secrete chemotactic agents that attract sperm.
____ has been shown to have chemotactic properties.
Only fertilizable follicles exhibit chemotactic activity.
Only capacitated sperm respond to these chemotactic signals, ensuring that the sperm are fully prepared for fertilization.
cumulus cells
Follicular fluid
Recognition of the Zona Pellucida Key Components:
______
is a protein on the surface of the sperm that is involved in binding to the zona pellucida, the outer layer surrounding the oocyte.
_____
is another sperm surface protein that plays a crucial role in the initial binding of the sperm to the zona pellucida.
SED1 (Sperm Surface Protein)
GalT (Galactosyltransferase)
Zona Pellucida Structure:
The zona pellucida is composed of ____, which are crucial for the sperm to recognize and bind to the oocyte.
glycoproteins
