Topic 3: Fertilization Flashcards by Miyaki Jan Lim

Formation of a new organism

FERTILIZATION

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Types of Fertilization

External fertilization (ex vivo)
Internal fertilization (in vivo)

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Types of Fertilization
Fish and amphibians
Challenge in aquatic vertebrates: release thousands of eggs in one spawning to ensure survival

External fertilization (ex vivo)

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Challenge in external fertilization: ensure species-specific attraction between sex cells

solution:

presence of chemoattractant released by jelly coat of the oocyte

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Types of Fertilization

External fertilization (ex vivo)

Release of eggs into the aquatic environment

Spawning

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Types of Fertilization
Avians and mammalians

Internal fertilization (in vivo)

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Types of Fertilization
Internal fertilization (in vivo)

Deposition of sperm cells into the female reproductive tract
Fertilization occurs in the oviduct or uterine/fallopian tube

Insemination

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Model ased on the studies of Oscar and Richard Hertwig

Sea urchin Fertilization

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Major events in Fertilization

Contact and recognition between ♂ and ♀

Regulation of ♂ entry into the ♀
Prevention to polyspermy (entry of more than one sperm into the oocyte)

Fusion of the genetic materials of ♂ and ♀
Pronuclear fusion / Amphimixis

Activation of ♀ metabolism to start development
2 Phases: Early and late metabolic responses of the oocyte

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Contact and recognition between ♂ and ♀

Acrosomal rection rundown

Starts with the breakdown of the acrosomal cap, releasing the
hydrolytic enzymes

Hydrolytic enzymes digest the jelly coat

Formation of acrosomal process which is a fibular protein to further penetrate the vitelline layer

Vitelline layer has the species-specific receptors for the sperm

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Contact and recognition between ♂ and ♀

Formation of fertilization cone

Fusion of the sex cells’ plasma membranes

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Movement of the sperm head into the cytoplasm of the oocyte causes what?

Causes cortical reaction

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Space between the plasma membrane and vitelline layer

Perivitelline space

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reaction where bursting of the cortical granules, releasing their chemical contents into the perivitelline space

Cortical reaction

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Vitelline layer is lifted off from the plasma membrane and forms the

fertilization envelope

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Chemical contents released into the perivitelline space

Proteases
Mucopolysaccharides
Peroxidases

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Chemical contents released into the perivitelline space

Breaks down molecular bonds between the vitelline envelope and plasma membrane

Proteases

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Chemical contents released into the perivitelline space

Produces osmotic gradients causing water to rush between the vitelline envelope and plasma membrane

Mucopolysaccharides

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Regulation of ♂ entry into the ♀

Chemical in nature
Lasts longer than 1st block

2nd block to polyspermy: Slow Block

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Chemical contents released into the perivitelline space

Hardens the fertilization membrane by crosslinking tyrosine residues of adjacent proteins
Prevents other sperms to attach to the oocyte

Peroxidases

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Regulation of ♂ entry into the ♀

Electrical in nature
Fast and transient, may not be sufficient
When the oocyte gets activated, Na+ channels open, causing Na+ influx into the cell
Inside the cell becomes more positive causing fertilization potential

1st block to polyspermy: Fast Block

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are already part of the early metabolic responses of the oocyte

1st and 2nd block to polyspermy

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2nd block to polyspermy: Slow Block rundown

Phospholipase C stimulation produces IP3 and DAG
IP3 causes Ca2+ release, thereby causing cortical reaction

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specific process where the Male and female pronuclei meets, forming the zygote nucleus

Study These Flashcards

Pronuclei fusion/Amphimixis

Fusion of the genetic materials of ♂ and ♀ rundown

When the sperm head gets into the oocyte cytoplasm, its compact head undergoes decondensation (nuclear breakdown) and starts to form the new male pronucleus At this point, the metaphase II arrest is lifted and the second polar body is released Protamines gets replaced with histones

Metabolic activation of the oocyte Early metabolic responses

Fast and slow block

Metabolic activation of the oocyte slow block _________ stimulation can also be triggered but not always certain unlike phospholipase C activation

Tyrosine kinase

Metabolic activation of the oocyte slow block ________ activate calcium-dependent kinases like NAD+ kinases that phosphorylate NAD+

Ca2+ ions

Metabolic activation of the oocyte slow block what can serve as a coenzyme involved in the synthesis of lipids. This lipid synthesis prepares the fertilized oocyte for the generation of plasma membranes of the newly formed cells. This process is essential with the onset of cleavage division and the succeeding stage of embryogenesis.

NADP+

Transport of Gametes & Fertilization in Mammals Fingerlike structures surrounding the ostium

Fimbriae

Metabolic activation of the egg is a wakeup call for the oocyte into a fast-paced action

Fertilization

what are the late metabolic responses of the oocyte in aquatic animals

Activation of protein kinase C and Ca2+ release also result in protein synthesis, DNA replication, and cytoplasmic movements hyaline layer

what are the late metabolic responses of the oocyte Basically similar pathway in mammals

Basically similar pathway in mammals Except formation of hyaline layer

Transport of Gametes & Fertilization in Mammals Oocyte transport in the

female reproductive tract

Transport of Gametes & Fertilization in Mammals Oocyte transport in the

Ostium

Transport of Gametes & Fertilization in Mammals During ovulation, oocyte released is captured by the _______ and travels down to the uterus

fimbriae

Transport of Gametes & Fertilization in Mammals It takes how many days for the oocyte to travel from the oviduct down to the uterus

4-5 days

Transport of Gametes & Fertilization in Mammals By around how many days is it already in the vicinity of the uterus

7 days

Transport of Gametes & Fertilization in Mammals Fertilization site of oocyte

Ampulla

Fertilized or not, the oocyte gets to travel down to the uterus

true

Sperm transport in the female reproductive tract once ________

inseminated

Site of insemination in the common mammals

Vagina

capacitation Length may vary form species to species Mouse Rabbits Humans

Mouse: 1 hr, Rabbits, 6 hr, Humans: 5-8 hr

Natural vaginal acidity becomes what pH after insemination

3.5 to 7.2 after insemination

Path of sperm

Upper vaginal canal → Cervix → Uterus → Uterotubal junction → Ampulla of the Fallopian tube

In the case of rodents, the site of insemination is in the

uterus

what happenes to Thick cervical mucus after insemination

- Insemination causes mucus to become watery which helps sperm to swim

In the ampulla, the sperm has what kind of motility to penetrate the oocyte

hyperactivated motility

Barriers in the reproductive tract:

Natural vaginal acidity Thick cervical mucus Wide uterus Utero-tubal junction Not much constricted in mammals compared to rodents

in mammals, sperm-specific receptor present in what layer of the egg?

In in vitro fertilization, the collected sperms are incubated in what medium

capacitation medium

Penetrating the mammalian zona pellucida involves other proteolytic enzymes like a sperm enzyme crucial for fertilization that helps sperm penetrate the egg's protective outer layer, the zona pellucida.

acrosin

Sperm undergo __________ along its journey in the female reproductive tract Period of conditioning for the sperms as they pass through

capacitation

Removal of glycoprotein coat and other seminal proteins that cover the acrosome cap

capacitation

Union of Gametes In mammals, what is is released from the acrosomal cap which Digests the corona radiata, ZP, and PM

Hyaluronidase

Accomplishments of Fertilization

Completion of the second meiotic block Metaphase II arrest is lifted off Restores normal diploid number of chromosomes 46 chromosomes Sex of the future embryo is determined Variation Metabolic activation of the egg

how does meiosis contribute to the gender babies have?

Meiosis determines the sex of a baby by producing gametes that carry either X or Y chromosomes. The sperm’s chromosome (X or Y) ultimately decides whether the baby will be female (XX) or male (XY).

Fertilization in Amphibians rundown

Fertilization → Ca2+ influx → Protein kinase II → Cytostatic factors degrade → Meiosis proceeds to complete

Topic 3: Fertilization Flashcards

(58 cards)