Gametogenesis Flashcards
Generally, what determines sex?
Which chromosome is inherited from the father
How did mapping of SRY occur?
By analyzing DNA of XX men and XY women
What conclusions were made in mice regarding SR Y function
It is necessary, sufficient, and expressed
True or false germ cell migration is identical in males and females
True
Describe primordial germ cells
Bipotential stem cells that divide while migrating
What determines whether PGC’s develop as eggs or sperm?
The gonad
True or false PGC‘s have their own migrating niche
True
Why is it important that PGC migrating niches have SCF secreting cells?
SCF is necessary for PGC motility and survival
Describe the migration of PGC’s
Originate in the hindgut and migrate through the dorsal mesentery into the gonad
When does spermatogenesis begin?
At puberty
How many sperm can be produced per second?
Over 1000
Outline the three phases of spermatogenesis.
Mitotic proliferation
Meiotic division
Differentiation
What are the cells called in spermatogenesis that undergo?Mitotic proliferation.
Spermatogonia
What type of cells undergo meiotic division
Spermatocytes
What cells undergo differentiation in spermatogenesis?
Spermatids
Outline the two ways in which meiosis differs from mitosis
Meiosis reduces chromosome number by half
And meiosis involves the recombination of maternal and paternal genetic material
Where does spermatogenesis take place?
In the seminiferous tubules
Outline the process of spermatogenesis
- Spermatogonia undergo Mitotic proliferation.
- Primary spermatocytes undergo the first meiotic division
- Secondary spermatocytes undergo the second meiotic division
- Spermatids differentiate into sperm.
How many spermatids are produced from one spermatogonium?
4
Describe the chromosome complement of spermatogonium
2n, 4c
Describe the chromosome complement of a primary spermatocyte.
2n, 4c
Describe the chromosome complement of the secondary spermatocyte
1n, 2c
Describe the chromosome complement of spermatids
1n, 1c
Describe the chromosomal complement of spermatozoa
1n, 1c
What are spermatids?
Immature haploid gametes
What are spermatozoa?
Haploid gametes
What is spermiogenesis?
Differentiation of sperm
List the five main events of spermiogenesis
Nuclear shaping and condensation
Formation of flagellum
Formation of the acrosome
Rearrangement of organelles
And shedding of the residual body
Describe the nuclear shaping and condensation phase of spermiogenesis
Changes in chromatin packaging from somatic histones to sperm specific protamines
Describe how the flagella is formed in spermiogenesis
Elongation of microtubules from the centriole at the base of the nucleus
Why is the acrosome important?
Contains enzymes needed for fertilization
Describe organelle rearrangement in spermiogenesis
Mitochondria form a ring at the base of the flagellum that will then fuel beating
Describe the shedding of the residual body in spermiogenesis
Most of the cytoplasm is absorbed by sertoli cells
Why is shedding of the residual body in spermiogenesis important
It makes sperm as aerodynamic as possible
How long does a spermatogenesis cycle take?
About 64 days
How long does spermatogonia mitosis take?
16 days
How long does the first meiotic division of spermatogenesis take?
24 days
How long does the second meiotic division of spermatogenesis take?
A few hours
How long does spermiogenesis take?
24 days
How many sperm are made in each testicle daily?
100 million
How many sperm are released in one ejaculation?
200 million
What happens to unused sperm?
It is re-absorbed or eliminated through urine
How much sperm can a human male produce in his lifetime?
10^13
What meiotic events occur in the oval during the foetal period?
The oogonium undergoes mitosis
What is the chromosome complement of the oogonium?
2n, 2c
What does Mitotic division of the oogonium produce
A primary oocyte
What is the chromosome complement of the primary oocyte?
2n, 4c
When does meiosis begin on the primary oocyte?
Before or at birth
What is the state of the primary oocyte after birth? Including chromosome complement.
Arrested in the diplotene stage of the first meiotic division, 2n, 4c
When does the primary oocyte complete the first meiotic division and begin the second?
After puberty
What is produced after the first meiotic division of the primary oocyte is complete?
Second oocyte and the first polar body
What is the chromosome complement of the secondary oocyte?
1n, 2c
In which stage of meiosis two is the secondary oocyte arrested in following ovulation?
Metaphase two
What does fertilization produce?
A fertilized ovum in the second polar body
When does the second meiotic division of the ovum take place?
After fertilization
What is the chromosome complement of the fertilized ovum?
1n, 1c from ovum and sperm
What is oogenesis?
The unequal meiotic divisions that release polar bodies without diminishing egg cytoplasm
What do follicle cells surround?
The differentiated egg
Why are follicle cells important
Critical for cell survival and fertilization
What are polar bodies?
Non-germ, daughter cells that receive DNA and not much else
What is the developmental role of polar bodies?
To reduce the genetic complement of the egg
What ends up happening to the polar bodies?
They may die off or be re-absorbed by the egg or embryo
What happens to unused oogonium?
They undergo atresia
What happens to oogonium between the second and fifth month of pregnancy?
Their numbers increase from a few thousand to 7,000,000, representing the maximum number of germ cells ever found in the ovaries
How is initiation of oogenesis different from initiation of spermatogenesis?
00, Genesis is initiated once in a finite cell population
Spermatogenesis is initiated continuously in a mitotically dividing stem cell population
How many gametes are formed in male and female gametogenesis per meiosis?
One in females 4 in males
How is completion of oogenesis different from completion of spermatogenesis?
Completion of OO Genesis is delayed for months or years
Completion of spermatogenesis is completed in days or weeks
How is gamete differentiation different in males and females?
Males: differentiation occurs while haploid, after meiosis ends
Female : differentiation occurs while diploid, in the first meiotic prophase
How was the first meiotic prophase different between males and females
In females, all chromosomes exhibit, equivalent, transcription, and recombination
In males, sex chromosomes are excluded from recombination and transcription
How many conceptions are estimated to abort spontaneously
1/3
About how many spontaneous abortions occur before pregnancy detection
1/4
How much of spontaneous abortions do chromosome abnormalities count for?
40 to 50%
Describe gamete’s resulting from non-disjunction
Have missing or extra chromosomes, or chromosomes with duplicated,, deleted, or rearranged segments
Define monosomy
Absence of a chromosome in a gamete
What is trisomy?
Two of the same chromosome in a gamete
What four things happen after gametogenesis
Final changes to sperm occur in the female body
Transport of gametes within the reproductive tract
Sperm and egg communicate to determine compatibility
Fertilization and zygote formation
