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
*what phase of mitosis
Here, each group of chromatids has reached one of the poles.
They will eventually form the chromosomes.
The chromosomes will then uncoil and lengthen, and a nuclear envelope re-forms in each of the daughter cells.
Telophase
-This process is where the daughter cells become haploid
-allow for genetic recombination (unique combination of parental genomes.)
-In females, it starts at the fetal stage, which then pauses and starts again during puberty, before ovulation.
-In males, it is not initiated until after puberty but it then becomes a continuous process.
meiosis
In ____, chromosomes separate to produce diploid daughter cells.
In ____, the sister chromatids results to haploid daughter cells.
Meiosis 1
Meiosis 2
in meiosis, what are the subdivisions of prophase
leptotene
zygotene
pachytene
diplotene
diakinesis
it is the pairing of two chromosomes
synapsis
point where chromosomes physically
cross
chiasma / (plural = chiasmata)
In meiosis
During anaphase, it is the ____ that are pulled apart to become grouped at the poles of the spindle during telophase.
homologous chromosomes
In males, at the end of telophase of meiosis I, the primary spermatocyte divides into two ____ by cytokinesis.
secondary spermatocytes
*Meiosis
In females, telophase is associated with a very uneven cytokinesis resulting in one of the two daughter cells being much larger than the other.
The larger daughter cell is now referred to as a ____ while the small daughter cell, which is almost devoid of organelles, is the ____.
secondary oocyte
first polar body
By ____ of meiosis II, the two chromatids of each chromosome have separated, and so each gamete receives only a single chromosome from each homologous pair.
telophase
In meiosis
The secondary spermatocyte divides into two ____.
spermatids
-specialized cell architecture
-forms oocytes from oogonia through oogenesis and spermatozoa from spermatogonia through spermatogenesis.
Cytodifferentiation
*Development of primordial follicles
Once in the female gonad, the primordial germ cells will be surrounded by follicular cells.
The PGCs become ____ and proliferates but does not undergo cytokinesis (they are still clumped).
oogonia
*Development of primordial follicles
They proliferate rapidly (millions) but will be followed by ____.
The surviving oogonia will differentiate into ____.
The remaining oocytes will form the ____.
apoptosis
oocytes
primordial follicles
*Follicle and Oocyte growth
The vast majority of follicles will degenerate through a process called ____
atresia
*Follicle and Oocyte growth
Once activated (around puberty), the follicles will form a cuboidal layer around the oocyte and is now called the ____
The cells surrounding the primary follicle will now be called ____
primary follicle
granulosa cells
*Follicle and Oocyte growth
The granulosa cells will proliferate and create the ____
The follicle will then create glycoproteins to surround the oocyte. The glycoproteins will form the ____
secondary follicle
zona pellucida
*Follicle and Oocyte growth
As development continues, fluid-filled spaces appear between the granulosa cells.
They will then merge into a single cavity, the antrum, characterizing the ____
tertiary follicle
*Follicle and Oocyte maturation
The tertiary follicle continues its development and, if selected for ovulation, enters a final phase.
This is stimulated by the what hormone
luteinizing hormone (LH).
*Spermatogonia and Seminiferous Tubules
The PGCs in the developing gonad become localized in the ____ of the primitive sustentacular cells (future Sertoli cells).
Before puberty, the cell cords will acquire a lumen and become the _____
cell cords
seminiferous tubules
is the process where spermatogonia becomes a spermatozoa.
Spermatogenesis
*Spermatogonia and Seminiferous Tubules
The sustentacular cells gradually assume the characteristics of Sertoli cells.
The PGCs will then develop into ____
spermatogonia
There are three types of spermatogonia:
Type A, intermediate and Type B.
what are the four stages of spermiogenesis
Golgi
Cap
Acrosome
Maturation
*which phase of spermiogenesis?
The acrosomal granule will flatten, and become the acrosome and will spread atop the nucleus.
One of the centriole will form the axoneme (flagellum).
Cap phase
*which phase of spermiogenesis?
The acrosome will cover majority of the elongating nucleus.
The neck and the annulus of the developing sperm emerges.
Note that many mitochondria are found around the cytoplasm.
Acrosome phase
*which phase of spermiogenesis?
The mitochondria will assemble in the middle piece.
The species-specific characteristics of the head and sperm of animals will be developed here.
Maturation phase
*which phase of spermiogenesis?
The Golgi apparatus produces an acrosomal granule that will be adjacent to the nucleus.
The centrioles in the cell will then move towards the opposite side.
Golgi phase
Meiosis
The Type B spermatogonia will become the ____
These cells will undergo meiosis I to become 2 secondary spermatocytes. These secondary spermatocytes will then create 2 spermatids each through meiosis II.
primary spermatocytes
