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BIOL 411 - Medical Embryology > Exam #2 - Worksheet 1 and 2 > Flashcards

Exam #2 - Worksheet 1 and 2 Flashcards

Cloning, Evolution, and Blastulation and Nontraditional fertility Methods

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USMLE® Step 1 flashcards
1
Q

What are the six steps that take place during fertilization?

A
  1. Initial contact between egg and sperm
  2. Entry of sperm into egg
  3. Prevention of polyspermy
  4. Metabolic activation of the egg
  5. Completion of meiosis by the egg
  6. Formation of pronuclei and pronuclei fusion
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2
Q

What are the male considerations in the first step in fertilization?

A
  1. initial contact between egg and sperm

-Need 60-100 million sperm/mL
Sperm Capacitation: Incubation within the female reproductive tract (5-6 hours in primates, 1 hour in mouse)
-Necessary for acrosome reaction and coagulation/liquification reaction
-Sperm swims for 72 hr, capable of fertilizing for 48hr (Positive rheotaxic response= swims against flow)
-Sperm agglutination: sperm stick together making it difficult for them to swim

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3
Q

What are the female considerations in the first step in fertilization?

A

-Vaginal contractions help propel sperm (there are prostaglandins in semen that can cause this)
-Low viscosity cervicle mucous midcycle
-If no chemoattractant from egg 50/50 chance of reaching the right tube
-Egg delivered into fallopian tube by cilliary beating
-Fertilizationg takes place in upper 1/3 of tube and egg is only “ripe” for 24 hr

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4
Q

What happens in the second stage of fertilization?

A
  1. Entry of sperm into egg

Sperm penetrate between cells of Corona Radiata
-noncapacitated sperm or sperm where acrosome reaction occured prematurely can not pass

Acrosome Reaction: Allows sperm to dissolve through Corona Radiata and Zona Pellucida (involves hyaluronidase and acrosin enzymes)

Sperm bind to the Zona Pellucida
ZP3 is one of three glycoproteins that make up the membrane surrounding the oocyte and it ensures that sperm of a dissimilar species do not penetrate the zona pellucida

Fusion of Sperm and Egg Plasma Membrane

TCTE-1 receptor: species specific binding of sperm with egg

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5
Q

What happens in the third stage of fertilization?

A
  1. Blocks to polyspermy

Fast Block
-2-3 sec, lasts for 60 seconds
-Influx of Na+
-Depolarization from -70mv to +10mv
-Helps repell sperm from attaching to Zona

Slow Block
-Ca2+ release by egg
-Causes rupture of cortical granuoles
-Causes conformational change of ZP3 receptors so sperm detach
-Plasma membrane hardens

Embryos that have dispermy usually abort

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6
Q

What happen in the fourth stage of fertilization?

A
  1. Metabolic activation of egg

-ZP3 receptor binding
-Na+ influx
-H+ efflux (increase in pH- becoming more basic)
-Acrosome rxn triggers membrane G proteins

~Second messenger systems:
-Protein Kinase C
-Inositol Tri Phosphate
^These cause Ca2+ release from E.R. and an increase in protein synthesis

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7
Q

What happen in the fifth stage of fertilization?

A
  1. 2nd Meiotic division complete

In this stage Meiosis II is finally completed in the egg.

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8
Q

What happen in the sixth stage of fertilization?

A
  1. “Fusion” of Pronuclei

-12 Hr in mammals
-Decondensation of egg and sperm chromatin
-Replication of DNA (anticipation of mitosis)
-Dissolution of both pronuclear membrane
-Formation of spindle fibers
-Mitosis “cleavage” resulting in 2 cells

First diploid nucleus is not seen in zygote stage… it’s seen in the two cell stage

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9
Q

What is Procardia and what does it do?

A

Procardia is a drug used as a male contraception
its a heart calcium blocker
-men on the drug have fertility problems
-prevents sperm acrosome reaction
-blocks penetration of zona pellucida

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10
Q

What are the fertility statistics for 1 year? 1 month? 3 months? 9 months?

A

90% conceive in 1 year
20% in 1 month
50% in 3 months
75% in 9 months

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11
Q

What 3 methods induce superovulation?

A
  1. GnRH Agonists (enhancers), “Lupron”
  2. Clomiphene Citrate “Clomid”
  3. HMG
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12
Q

What is GnRH Agonists, “Lupron” and what is used for? How does it work?

A

its an enhancer and it is used to induce superovulation
-Powerful, directly stimulate LH, FSH output
-Can overstimulate ovary to produce too many eggs per cycle (10-20)
-Ovarian Hyperstimulation Syndrome (OHSS): excessive fluid into abdomen tends to thicken blood, risk of stroke

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13
Q

What is Clomphene Citrate “Clomid” and what is used for? How does it work?

A

Used to induce superovulation
-Milder stimulation, oral medication that competes with estrogen at Ant. Pit. suppressing its negative feedback
-Increases output of LH, FSH
-Multiple ovulation (6-8 eggs/cycle)

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14
Q

What is GnRH Agonists, “Lupron” and what is used for? How does it work?

A

used to induce superovulation
-LH, FSH from menopausal urine
-Not really used anymore
-hCG given on last day triggers ovulation

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15
Q

What are the 4 techniques used for mammalian cloning?

A
  1. Cleavage separation (Embryo Twinning)
  2. Nuclear transfer (Wilmut Method “Dolly the Sheep”)
  3. “Therapeutic” Cloning
  4. Parthenogenesis
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16
Q

What is Cleavage Separation? How does it work?

A

a mammalian cloning technique
also known as embryo twinning

  • strip zona off at 2 cell stage
  • separate blastomeres
  • add artificial zona
  • culture new embryos
17
Q

What is Nuclear Transfer Technique? How does it work?

A

a mammalian cloning technique
also known as the Wilmut Method “Dolly the Sheep”

  • culture mammary tissue on minimal media
  • starve cells into quiescent state
  • irradiate nucleus into egg
  • stimulates w electricity
  • culture or implant in uterus of surrogate mother
18
Q

What is “Therapeutic” cloning? How does it work?

A

a mammalian cloning technique

  • same as nuclear transfer technique
  • Rather than growing infant, embryo is separated into blastomeres
  • Blastomeres used to grow embryonic stem cell lines
  • Could be used for growing organs for transplant
19
Q

What does Parthenogenesis mean? what is it and how does it work?

A

It means an egg is hatched without ever being fertilized, think of the komodo dragons.

a mammalian cloning technique

  • can use chemicals, electricity, or other stimulants to make egg act as though it is fertilized
20
Q

20% of infertility problems are due to issues with:

A
  • Varicocele
  • cervical mucous
  • infection
  • male or female antisperm antibodies
21
Q

What are the 3 egg classifications by their yolk amounts? Examples?

A

Microlecithal: Small amount of yolk
-amphioxus and mammals

Mesolecithal: Moderate amount of yolk
-amphibians, cyclostomes(lamprey), lung fish

Macrolecithal: Large amount of yolk
most fish, reptiles, aves, and monotremes

22
Q

What are the 3 egg classifications by their yolk distribution? Examples?

A

Oligolecithal (isolecithal): even yolk distribution
-Most microlecithal eggs

Telolecithal: Uneven yolk distribution
-Most mesolecithal and macrolecithal eggs

Centrolecithal: Central yolk distribution
-Insects and Arthropods

23
Q

How many days prior to ovulation is yolk produced?

A

7 - 8 days prior

24
Q

What triggers yolk production?

A

estrogen from follicular cells

25
Q

How is Yolk produced?

A
  • Estrogen acts on liver
  • Liver produces Vitellogenin
  • Vitellogenin transferred via blood to follicular cells
  • Vitellogenin added to oocyte to form yolk platelets
26
Q

What are the two types of egg retention? What do they mean?

A
  1. Oviparity
  2. Viviparity
27
Q

What are the two types of Viviparity? What do they mean?

A
  1. Ovoviviparity
  2. Euviviparity
28
Q

What are the arrangements of the cell during cleavage?

A

Long axis of mitotic spindle tends to parallel long axis of cell

Mitotic spindles tend to swing at right angles to previous division

Plane of cytokinese is perpendicular to long axis of spindle

29
Q

What are the results of cleavage

A

In Morula: mass of cells, usually 32-64 cell stage
In Blastula: mass of cells w hollow center, 128 cell stage

30
Q

What are the results of cleavage

A

In Morula: mass of cells, usually 32-64 cell stage
In Blastula: mass of cells w hollow center, 128 cell stage

BIOL 411 - Medical Embryology (5 decks)

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