3B Gametes and Fertilisation Flashcards

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1
Q

gametes

A

male and female sex cells found in all organisms that reproduce sexually

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2
Q

why is it important that gametes only have 1 set of chromosomes?

A

during fertilisation ZYGOTE is created with FULL NO. of chromosomes

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3
Q

adaptions of egg cell?

A
  • zona pellucida -> protective glycoprotein layer that sperm have to penetrate
  • follicle cells -> form protective coating
  • lipid droplets -> huge food store to nourish developing embryo
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4
Q

adaptions of sperm cell?

A
  • lots of mitochondria -> provide energy for tail movement
  • acrosome -> contains dig. enzymes used to break down zone pellucida so sperm can penetrate egg
  • flagellum -> allows sperm to swim towards egg cell
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5
Q

what is the acrosome reaction?

A
  1. sperm hits zona pellucida
  2. chemicals released from follicle cells
  3. acrosome swells and fuses with sperm cell membrane
  4. dig enzymes released and digest through follicle cells and zona pellucida
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6
Q

describe cortical reaction

A
  1. egg releases cortical granules from vesicles
  2. makes zona pellucida harden -> other sperm cannot get through -> so only one sperm fertilises egg
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7
Q

fertilisation

A

when nuclei of egg and sperm cell fuse -> forming ZYGOTE!!

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8
Q

explain why exposing pregnant mice to cig smoke affects fertility of MALE OFFSPRING

A
  1. fewer stem cells producing sperm = fewer sperm made
  2. less mobile sperm = less sperm reaching egg
  3. poor ability to cross zona pellucida
  4. LESS CHANCE FERTILISATION
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9
Q

describe the process of fertilisation
(4 marks)

A
  1. sperm swim towards egg in oviduct
  2. acrosome reaction occurs when sperm reaches zona pellucida -> dig enzymes released
  3. enzymes digest through zona pellucida so sperm can enter egg cell
  4. sperm head fuses with cell membrane of egg cell -> triggers cortical reaction
  5. chemicals released from cortical granules make zona pellucida harden -> prevents polyspermy
  6. only sperm nucleus enters egg - tail discarded
  7. nucleus of sperm fuses with nucleus of egg cell
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