What is the first stage of fetilisation in mammals?
Acrosome reaction
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What is the description of the acrosome reaction?
The acrosome releases digestive enzymes when sperm head meets the zona pellucida of the egg, enzymes digest a channel in the zona pellucida for sperm to burrow through to the cell surface membrane of egg cells
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What happens after the acrosome reaction?
Membranes fuse
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What happens when the membranes fuse?
Cell surface membrane of sperm and egg fuse enabling haploid nucleus from sperm tow inter cytoplasm of egg cell
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What happens after the membranes fuse?
Egg cell response
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What happens in the Egg cell response?
Special vesicles move towards and fuse with the cell surface membrane
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What is another name for the vesicles?
Cortical granuales
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What do these Granules do?
They release their contents which causes a change in surface layers of egg that stop other sperm from entering the cell
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How do they release their content?
through exocytosis
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What happens after the egg cell response?
Meiosis restarted
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What does this mean?
The presence of the sperm nucleus in the cytoplasm of the egg cell causes the second division of meiosis to occur
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What happens in fertilisation?
A diploid number is formed
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What nucleus under goes mitosis?
Generative nucleus
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What is produced?
Two male gamete nuclei
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What happens after pollen lands of the stigma?
The pollen tube begins to grow toward embryo sac
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Where does the pollen tube go down?
It goes down the style
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What does it do?
It produces enzymes and digests style tissue and uses the products to continue tube growth
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Where are the haploid nuclei?
Near the tube tip
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What does the pollen tube nucleus control?
growth
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What happens in the ovule?
It fuses and the pollen tube nucleus breaks down
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What does the Generative nucleus do?
produces two male gametes
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What does the first male gamete do?
fuses with female gamete nucleus and produces a diploid zygote
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What does the second male gamete do?
fuses with two polar nuclei
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producing what?
triploid primary endosperm nucleus
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What are the two ways genetic variation is achieved?
Crossing over and independent assortment
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What happens in crossing over?
During the first division in meiosis, pairs of chromosomes, known as homologous chromosomes, line up and may swap part of their genetic information
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What happens in independent assortment?
During the first division of meiosis, each homologous pair of chromosomes can line up
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Other cards in this set
Card 2
Front
What is the description of the acrosome reaction?
Back
The acrosome releases digestive enzymes when sperm head meets the zona pellucida of the egg, enzymes digest a channel in the zona pellucida for sperm to burrow through to the cell surface membrane of egg cells
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