Random chromosome segregation generate the diversity in gametes as well as chromosomes paring up. This happens 2-3 times per chromosome. Combinations of maternal and paternal genes.
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XO Karyotype
The only case where missing a chromosome is tolerated.
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Trisomy
3 copies of a chromosome e.g Downs Syndrome. Mostly fatal. 16 is a common cause of miscarriages.
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Spermagtogensis
Sperm develop in testicles in coiled tubes called seminiferous tubules.
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Oogenesis
An ovum develops in the ovary. The secondary oocyte is the stage released by the ovary during ovulation.
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Zona pellucida
Glycoprotein coat surrounding the oocytes plasma membrane. Docking proteins allow sperm to bind here, which triggers an acrosome reaction.
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Acrosome Reaction
Releases enzymes from the sperm head which breaks the ZP. Sperm can enter the plasma membrane and fuse to the egg.
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Cortical Reaction
Granules under the egg membrane are released, destroy the sperm docking proteins, preventing more sperm binding. Prevents polyspermy (fatal).
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Post-Fertilisation
Polar body of the oocyte can maintain its size. DNA is replicated beginning the first mitosis. All paternal mitochondria will be destroyed, leaving only maternal mitochondria.
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Compaction
First division the zygote will divide but not increase in size.
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Cleavage
Cells undergo mitosis without growth. Creates cells called blastomeres
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Morula
16 cell stage, compact ball of cells.
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Inner Cell Mass
Cells in the middle are fated to become the embryo.
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Trophoblasts
Cells on the outside are fated to become supporting structures.
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Day 4
Trophoblast cells pump Na+ into the centre of mourla drawing in water, creates a hollow ball of cells and central fluid filled cavity, known as blastocyst cavity.
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Day 5
Blastocyst hatches out of the ZP
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Implantation
Blastocyst needs nutrient and must excrete waste, cell must implant and link itself to the maternal blood supply. Hatching -> Apposition -> Adhesion -> Invasion.
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Trophoblasts
Two types cytotrophoblasts (retain their membranes) and syncytiotrophoblats (multinuclear cells).
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Bilaminar Disc
Inner cell mass differentiates into the epiblast (dorsal) and hypoblast (ventral)
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Ectopic Pregnancy
Fertilised egg implants itself outside of the womb, normally in the fallopian tubes. Impossible to save the pregnancy. Treatment: monitoring-> medication (methotrexate) -> surgery (keyhole surgery)
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Twinning
More structures shared between the embryos means a higher risk. Splitting can also be incomplete leading to conjoined twins.
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Epiblast
Derived from inner cell mass and lies above the hypoblast. Gives rise to three primary germ layers (ectoderm, definitive endoderm and mesoderm).
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Hypoblast
Tissue type forms from the inner cell mass. beneath the epiblast and consists of small cuboidal cells.
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Other cards in this set
Card 2
Front
The only case where missing a chromosome is tolerated.
Back
XO Karyotype
Card 3
Front
3 copies of a chromosome e.g Downs Syndrome. Mostly fatal. 16 is a common cause of miscarriages.
Back
Card 4
Front
Sperm develop in testicles in coiled tubes called seminiferous tubules.
Back
Card 5
Front
An ovum develops in the ovary. The secondary oocyte is the stage released by the ovary during ovulation.
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