3B Gametes and Fertilisation Flashcards
1
Q
gametes
A
male and female sex cells found in all organisms that reproduce sexually
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
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
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
5
Q
what is the acrosome reaction?
A
- sperm hits zona pellucida
- chemicals released from follicle cells
- acrosome swells and fuses with sperm cell membrane
- dig enzymes released and digest through follicle cells and zona pellucida
6
Q
describe cortical reaction
A
- egg releases cortical granules from vesicles
- makes zona pellucida harden -> other sperm cannot get through -> so only one sperm fertilises egg
7
Q
fertilisation
A
when nuclei of egg and sperm cell fuse -> forming ZYGOTE!!
8
Q
explain why exposing pregnant mice to cig smoke affects fertility of MALE OFFSPRING
A
- fewer stem cells producing sperm = fewer sperm made
- less mobile sperm = less sperm reaching egg
- poor ability to cross zona pellucida
- LESS CHANCE FERTILISATION
9
Q
describe the process of fertilisation
(4 marks)
A
- sperm swim towards egg in oviduct
- acrosome reaction occurs when sperm reaches zona pellucida -> dig enzymes released
- enzymes digest through zona pellucida so sperm can enter egg cell
- sperm head fuses with cell membrane of egg cell -> triggers cortical reaction
- chemicals released from cortical granules make zona pellucida harden -> prevents polyspermy
- only sperm nucleus enters egg - tail discarded
- nucleus of sperm fuses with nucleus of egg cell
