Lec.4 GAMETOGENESIS Flashcards
At fertilization, the maternal and paternal genomes are united in the one-cell fertilized ovum, forming the ____.
In order for fertilization to occur, specialized cells have been developed by the body, known as ____.
zygote
gametes
-These cells are the predecessors of the female and male gametes.
-remains pluripotent, even When the embryo differentiates into the somatic germ layers,
-During gastrulation, they will emerge at the posterior rim of the embryonic disc.
-They will then migrate to the the yolk sac and allantois, outside the embryo.
-After a while, they will then populate the developing gonad.
-During and after their migration, the these proliferate by mitosis.
primordial germ cells
this provides nutrients and oxygen
to the developing embryo.
Yolk sac
what is responsible for gas exchange and storage of liquid waste.
Allantois
what makes up the chromosomes
DNA and proteins
what determines the trait of the developing embryo.
chromosome
One pair of chromosomes comprises the sex chromosomes, while the others are referred to as ____.
autosomes
Divisions of cells occur through mitosis which transfers a _____ copy of the chromosome to each of the daughter cells.
During gametogenesis, however, meiosis becomes responsible for producing the ____ copies in the germ cells.
diploid
haploid
Interphase is subdivided into:
gap phase 1 (G1)
DNA-synthesis phase (S)
gap phase 2 (G2)
*which phase of interphase?
The cell undergoes rapid growth and is metabolically active.
Amino acids and proteins needed for DNA replication are synthesized during this phase.
This is the longest phase.
G1 phase
*which subdivision of interphase?
Sometimes cells will go to this phase.
Cells may remain in this phase for long periods of time, even indefinitely.
Cells that are highly differentiated may also enter here such as the neurons (unable to replace damaged ones).
G0 phase
*what phase of interphase
DNA replication occurs for the two genetically identical daughter cells.
Here, each chromosome produces two chromatids.
When the DNA is replicated, both strands of the double helix are used as templates to produce two new complementary strands.
S phase
*which subdivision of interphase?
This is a shortened growth period in which many organelles are reproduced or manufactured.
Parts necessary for mitosis and cell division are made here.
After this phase, the mitotic phase begins (karyokinesis + cytokinesis).
G2 phase
This process divides the diploid chromosome of a cell evenly between its daughter cells.
mitosis
it is the division of cytoplasm
cytokinesis
it is the process where the nucleus of a cell gives rise to a nucleus in each of its daughter cells.
karyokinesis
*what phase of mitosis
the chromosomes coil, contract, condense and thicken.
The centrioles present in the cell duplicates in the cytoplasm, the resultant two pairs become arranged at opposite poles of the nucleus.
The microtubules starts to form from the two pairs of centrioles and the nuclear envelope begins to dismantle.
Some microtubules will then attach to the kinetochores of the chromatids which will create the mitotic spindle.
This part is often called the prometaphase.
Prophase
At this phase of mitosis, chromatids align at the equatorial plane, or center of the cell.
The microtubules that did not attach to the kinetochores attach to each other and elongate the cell.
Metaphase
*what phase of mitosis
The centromeres present in the chromosomes divide.
The chromatids separate and, pulled by the microtubules, start to migrate towards the spindle poles.
Anaphase