Genetics - Fertilisation Flashcards
What is fertilisation?
It involves two haploid cells forming one diploid cell
What is a zygote?
It forms when a sperm penetrates the outer surface of any egg
What does a zygote divide into? When does this occur?
Morula
Day 4
What is a morula?
A solid ball of cells
What process occurs in the morula? What is this?
Compaction
It is the process of cells condensing and becoming less distinctly defined
What does a morula divide into? When does this occur?
Blastocyst
Day 5
What does the blastocyst separate into?
Inner cell mass (embryoblast)
Outer layer of cells (trophoblast)
What does the trophoblast form?
Placenta
What does the embyroblast form?
Embryo
What occurs during gestation week one?
Implantation
In which part of the uterus does implantation occur?
Anterior/superior walls
What occurs during gestation week two?
Formation of bilaminar disk
What three events occur during gestation week three?
Formation of primitive streak
Formation of notochord
Gastrulation
What is gastrulation?
It is a process that converts a ball of cells into a multi-layered organism
What three events occur during gestation week four?
Limb buds begin to form
Neural tube closes
Heart begins to beat
What is neurulation?
It is the process of neural tube formation, which is primarily through folding of the neuroectoderm
What two events occur during gestation week ten?
Genitals are differentiated
Intermittent breathing movements
What determines whether an embryo is male or female?
Whether the sperm contains an X or Y chromosome
What is the karyotype of males?
XY
What is the karyotype of females?
XX
What is X-inactivation?
It is a process that occurs in females during embryonic development resulting in one X chromosome in each cell being inactivated so the cells have a single working copy of the X chromosome genes
Why is X-inactivation important?
It ensures that the females have exactly the same level of gene products as a male
