Animal Repro > Fertilization > Flashcards

Fertilization Flashcards

(25 cards)

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1
Q

Know the important events involved in fertilization

A
  1. Capacitation
  2. Sperm penetration between cumulus cells
  3. Sperm attachment to zona pellucida
  4. Sperm penetration to zona pellucida
  5. Fusion of sperm and oocyte membranes
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2
Q

Supplementary sperm

A

-Extra sperm pass through the Zona Pellucida into the Perivitelline space
-May not cause issues

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3
Q

Supernumerary sperm

A

-Extra sperm which succeed in entering the Vitellus
-Such ova are said to show polyspermy

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4
Q

Know the different types of twins and how they come to be

A

-Monozygotic
-Dizygotic

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5
Q

Monozygotic

A

-A fertilized single egg splits into two developing zygotes
-Very early stage
-Identical twins
-Same sex

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6
Q

Dizygtic

A

-Result from the fertilization by two sperm of two separate ova that have reached maturation at the same time
-Not identical twins
-Can be different sexes
-Incidence increases with age of mother

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7
Q

Know the characteristics of the cumulus cells in the cumulus-oocyte complex.

A

-Embedded in an Extracellular Matrix (ECM)
-Contains hyaluronic acid

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8
Q

Know the purposes/characteristics of ZP-1, ZP-2 and ZP-3

A

-ZP1: Structural support
-ZP2: Helps an acrosome reacted sperm move through the zona
-ZP3: Binds to a receptor on the sperm plasma membrane and induces the acrosome reaction

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9
Q

Know how the acrosome reaction progresses

A
  1. Sperm contacts the Zona Pellucida
  2. Perforations develop on acrosome
  3. Plasma membrane fuses with the outer acrosomal membrane and creates point fusions.
    -Enzymes can escape and enables sperm to penetrate the Zona Pellucida
    ~Modifies equatorial segment so that it can later fuse with plasma membrane of oocyte
  4. The vesicles then slough and leave other structures intact including the Inner acrosomal membrane, Equatorial segment, and Post nuclear cap
  5. Zona Pellucida remains mostly intact
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10
Q

Know steps of fertilization following acrosome reaction

A
  1. Proacrosin converts to acrosin by Acrosin hydrolyzes Zona proteins
  2. Sperm enters Perivitelline space and settle into bed of microvilli
  3. Plasma membrane of oocyte fuses with membrane of equatorial segment and Polyspermy is blocked
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11
Q

Know what happens after sperm is engulfed

A

-2nd meiotic division is completed
-Sperm nucleus de-condenses and disulfide cross-linking is reduced by glutathione
-Male pronucleus forms
-Syngamy occurs

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12
Q

Define/describe syngamy

A

-The fusion of the egg and sperm pronuclei to form a diploid zygote
-Membranes of the pronuclei break down
-Chromosomes condense and arrange themselves for mitotic cell division
-On membrane dissolution there is one diploid (2n) cell
-First cleavage follows shortly and leaves two cells each with 2n chromosomes

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13
Q

Know some examples of how fertilization can go away

A

-Too many sperm
-Infertility
-Bad timing
-Ectopic pregnancy

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14
Q

How does too many sperm cause fertilization to go away?

A

-Dispermy
-Triploidy
-Leads to spontaneous abortion: Most cases

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15
Q

How does bad timing cause fertilization to go away?

A

-Most sperm can only survive 48 hours within the female genital tract
-In vitro studies show the ovulated egg cannot be fertilized after 24 hours

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16
Q

How does cause ectopic pregnancy fertilization to go away?

Study These Flashcards
A

-Fertilization occurs outside the oviduct
-Implantation may occur in the wrong location
-If oviducts are scarred fertilized ovum may implant in the fallopian tube

17
Q

Know what polyspermy is and why it is important to block it.

Study These Flashcards
A

-The fertilization of an egg by multiple sperm.
-Extra sperm entered the vitellus
-These embryos almost always abort

18
Q

How is polyspermy blocked?

Study These Flashcards
A

-Zona block
-Vitelline block

19
Q

Zona Block

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A

-Cortical granule components alter zona receptors
-Other sperm can’t penetrate zona
-Slow block
-Most important in sheep, cows, pigs, and dogs

20
Q

Vitelline block

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A

-Cortical granules fuse to vitelline membrane
-Becomes less penetrable to sperm
-Fast
-Most important in rabbits

21
Q

In what species is zina and vitelline block equally important?

Study These Flashcards
A

In rats and mice

22
Q

Know factors that reduce the effectiveness of the block to polyspermy

Study These Flashcards
A

-Age of ova
-Heat (temp)
-Excessive sperm numbers

23
Q

How does age of ova reduce the effectiveness to block polyspermy

Study These Flashcards
A

-Time of insemination relative to ovulation
-Aged oocyte increases chance of polyspermy

24
Q

How does heat reduce the effectiveness to block polyspermy

Study These Flashcards
A

-Increases metabolism and lifespan of egg
-Fever or Environment effect on body temperature

25
How does excessive sperm numbers reduce the effectiveness to block polyspermy
Previous barriers were ineffective
Animal Repro
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