Following fertilization, when do the primordial germ cells first appear?
Endodermal layer of yolk sac
24 hrs after fertilization
Trace the migration route of the primordial germ cells into the developing gonads from the yolk sac
Endodermal yolk sac ---> hind gut epithelium via dorsal mesentery ---> developing gonads
What are the stages of meiosis? List substages of prophase with what occurs at each stage
(Little Zebras Play Dirty Deeds)
Leptotene - chrom begin to coil, each chrom = 2 chromatids
Zygotene - homologous chrom pair (synapsis), synaptonemal complex forms
Pachytene - tetrads, start of crossing-over
Diplotene - crossing-over, chiasmata well defined
Diakinesis - finish crossing-over, nuclear membrane disrupted, spindle apparatus
What are the major events in meiosis?
List the major results of meiosis?
- Synapsis (pairing of homo. chrom.), crossing-over, two cell divisions w/ 1 DNA replication cycle (n)
- Non-identical and haploid daughter cells, increase in cell number
Define aneuploidy and euploidy, what are the types?
Euploidy - changes in complete set # of chromosomes
- Monoploidy, Diploidy (normal), Polyploidy
Aneuploidy - abnormal chrom. number (via nondisjunction)
- Monosomy, Trisomy
Compare the total number of oocytes that are present early in embryonic development to the number present at birth and prior to puberty.
Embryonic midterm - 7 million
Birth - 2 million
Puberty - 400,000 (arrested in diplotene)
Post-puberty - 400
Most become atretic
Describe the structure/layers of the mature follicle
external ---> internal
Theca externa - produce angiogenesis factor
Theca interna - LH receptors, secrete testosterone
Mural granulosa cells - FSH receptors
Cumulus/Oophorus cells - facilitates release of ovum at ovulation
Describe the meiotic state of the oocyte at puberty and prior to ovulation
Until puberty - diplotene of prophase I (primary oocyte)
Pre-Ovulation - metaphase II (until fertilization)
What is the role of LH in ovulation?
LH surge occurs causes ovulation; resuming of meiosis to arrest in Metaphase II - shuts down gap junctions b/w granulosa cells and oocyte, reducing [cAMP], allowing MPF activation
What are the factors that lead to meiotic arrest at the diplotene stage of meiosis
Hight [cAMP] from oocyte and follicular cells (inactivating MPF)
cGMP from follicular cells that inactivate phosphodiesterase 3A in oocyte (preventing the conversion of cAMP to 5'AMP, maintains high [cAMP]
What are the fates of the follicle after ovulation occurs?
Becomes the corpus luteum and secretes progesterone
Define, compare, and contrast spermatogenesis and spermiogenesis
Spermatogenesis - Development of mature sperm
Spermiogenesis - maturation of spermatids to motile spermatozoa
List the stages of spermatogenesis (5)
Primordial germ cells (2N); developing yolk sac
Spermatogonia (2N); Type A stem cells, Type B
Primary Spermatocytes (2N, 4c); meiosis I
Secondary Spermatocytes (N, 2c); meiosis II
Spermatids (N, 1c); x4 cells
List the two major differences between one cycle of oogenesis and once cycle of spermatogenesis
Two secondary spermatocytes (1n, 2c)
1 secondary oocyte + polar body
What is the location and function of the cells of Leydig?
Interstitial cells inside the testis
List the four stages of spermiogenesis and the major events that occur during each of the four stages
GCAM - Girls Call Abnormal Men
- Golgi phase - proacrosomal vesicles, acrosomal vesicles
- Cap phase - mature acrosome forms a cap over nucleus
- Acrosomal phase - sperm rotates so that acrosomal pole faces wall of seminiferous tubule, cytoplasm eliminated from tail for motility
- Maturation phase - completion of flagellum and nuclear condensation
Where are sertoli cells located?
Seminiferous tubules of the testes
What are the functions of the sertoli cells? (6)
- Physical support and maintenance
- Maintain and coordinate spermatogenesis
- Secrete estrogen, inhibin, and anti-Mullerian factor
- Maintain the blood-testes-barrier
- Secrete tubular fluid
- Phagocytize residual bodies of sperm cells
What is the role of testosterone in the blood testes barrier?
Stimulates the formation of a new BTB closer to the basal lamina
What is the action of LH on interstitial cells and Sertoli cells in regards to sperm cell production?
LH - activates LH receptors on interstitial cells of Leydig, causing cholesterol synthesis
Sertoli cells receive the testosterone and to secondary sex tissues
Based on your knowledge of paralogous groups, which gene would be expressed most anteriorly in the embryo?
Which of the following produces testosterone in the testis?
Cells of Leydig
What forms the corpus luteum?
Thecal and granulosa
What the the site of fertilization?
In mammalian embryo, unlike non-mammalian and invertebrates, most transcription via the embryonic genome as opposed to maternal genome, occurs as early as which...
In drosophila, from which of the following categories are mRNAs derived from maternal genome rather than embryonic?
Pair rule genes
Which of the following is a TF
Zinc fingers or helix loop helix arrangements are characteristic of members of which class of molecules?
None of the above
Shh is produced in which signaling centers
Floor plate of the neural tube
Zone of polarizing activity in limb bud
All of the above
All of the above
The principal energy source for ejaculated spermatozoa is
Prostatic acid phosphatase
Prostatic citric acid
Fructose seminal vesicle fluid
Fructose seminal vesicle fluid