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22 Cards in this Set

  • Front
  • Back
Primordial Germ Cells (PGCs) - where do they arise, where to they migrate, and what types of cells do they develop into
-Arise in wall of Yolk Sac
-Migrate to developing Gonad
-This special population of somatic cells set aside early in development to become gametogenic cells (gametes) lines in ovary (Oogonia) and testis (Spermatogonia)
How do PGCs, Oogonia, and Spermatogonia proliferate?
-PGCs proliferate by Mitosis (46 --> 46)
-Oogonia and spermatogonia (diploids) also mitotically active but then enter Meiosis (46 --> 23)
Gametogenesis - when haploid (23) gametes recombine, diploidy is reestablished in the...
Basics of Mitosis
-Mitosis involves 1 cell turning into 2 cells, each with 46 cells
Basics of Meiosis (Steps) (5)
-Diploid Oogonia and Spermatogonia are mitotic cells. They divide and make more of each other but eventually make diploid primary 'cytes.
-Diploid primary 'cyte has chromosome duplication, which turns it into a tetraploid cell (4N) temporarily b/c centrioles don't divide until later.
-Then Meiosis I occurs in which the primary 'cyte turns into a secondary 'cyte. -Secondary 'cytes turn into diploid cells(2N) (secondary 'cytes are haploids but with 2 chromatids, so 2x the amount of chromatids, so are technically diploids)
-Then the diploid cell undergoes Meiosis II where centromeres divide producing 2 haploid gametes (1N DNA) per every 1 secondary 'cyte (so total of 4 haploid cells)
Changes from PGC to Gametes (5)
-One PGC becomes one 1° ‘Cyte
-Homologous chromosomes pair (crossing over = variability) and then DNA duplicates
-One 1° ‘Cyte divides to produce two 2° ‘Cytes- homologs separate without centromere division
-Two 2° ‘Cytes each divide to produce two haploid gametes-centromeres divide to separate duplicated DNA strands
-Thus, one 1° ‘Cyte yields four gametes
STUDY Ploidy Changes in Meiosis slide chart (#11)
STUDY Ploidy Changes in Meiosis slide chart (#11)
Oogenesis - how many gametes produced, what type of divisions, how long does process last in human, what other types of cells does it produce
-1 gamete/month
-Unequal divisions - 1 large oocyte turns into 1 large ovum and 3 small polar bodies
-Menarch to menopause - start of menstruation at age 12, menopause at 52 (about 40 yrs)
-Produces few food/developmental information-rich cells
Spermatogenesis - how many gametes produced, what type of divisions, how long does process last in human, what other types of cells does it produce
-Equal divisions
-Puberty to death
-Produces many mobile cells to penetrate eggs
First and Second Maturations of Oocytes
-Primary oocyte contain 46 double-structured chromosomes
-After first maturation, secondary oocyte (has 23 double-structured chromosomes) and one polar body is produced (unequal division)
-After second maturation division, mature oocyte is produced that has 23 single chromosomes (22 + X) plus 3 polar bodies (unequal division)
First and Second Maturations of Spermatocyte
-Primary spermatocyte after DNA replication has 46 double-structured chromosomes
-After first maturation division, 2 secondary spermatocytes (equal division) are produced, each with 23 double-structured chromosomes
-After second maturation division, 4 spermatids (equal division) are produced, each with 23 single chromosomes (22 + Y) and (22+X)
Oogenesis - where does it occur, what drives it (2), what else drives cyclic changes in rest of female reproductive system
-Occurs in ovary
-Driven by pituitary secretions LH/FSH
-Estrogens and Progesterone (steroid hormones), produced in ovary, drive cyclic changes in rest of female reproductive system
Oogenesis - What does PGC turn into, when do the first and second meiotic divisions occur, what does that mean for primary oocytes and trisomy
-PGC -> Oogonium -> Primary Oocyte (these form Prenatally, not postnatally)
-First meiotic division just prior to ovulation (doesn't end until immediately before ovulation occurs)
-Second meitoic division only after Fertilization
-Thus, many primary oocytes arrested for long periods in Synapsis Of Meiosis I (so could be up to 40 years)
-Thus, increasing frequency of trisomy with Maternal Age
Ovulation Steps (6)
-Occurs at Mid-Cycle
-Secondary oocyte bursts through surface of ovary
-Secondary Oocyte (and 1st polar body)
-Surrounded by Zona Pellucida
-Granulosa Cells attached to zona pellucida as corona radiata
-Some mucoid Liquor Folliculi attached to corona radiata
Spermatogenesis - newborn seminiferous epithelium has what two types of cells, prepubertal seminiferous has what two types of cells, what triggers spermatogenesis and when
-Newborn seminiferous epithelium has Sertoli Cells and PGCs
-Prepubertal seminferous epithelium has Sertoli cells and Spermatogonia
-At Puberty, testosterone secretion triggers spermatogenesis (only at puberty do the spermatogonia receive proper amounts of hormone to develop/mature)
-Now seminifierous epithelium has all stages
Cytoplasmic Bridges
When spermatogonia are dividing, up through spermatids, until they become spermatozoa, cytoplasmic bridges join the clones of cells in each succeeding division. This allows for coordination of developmental stages.
Spermatogenesis - Once Spermatids are formed, Spermiogenesis leads to the formation of what, what happens to cell organelles and what do they produce (4)
-Once Spermatids are formed, Spermiogenesis results in formation of Spermatozoa
-Nuclear Condensation and streamlining
Golgi apparatus gives rise to Acrosome, which is the covering of the head of the spermatozoa - contains enzymes to break through pellucid zone of the oocyte
-Centrioles give rise to Flagellum
-Mitochondria give rise to Midpiece - midpiece of the flagella is a ring of mitochondria which powers the flagella
Nondisjunction - whta happens, what is trisomy, what is monosomy
-Unequal Distribution of chromosomes in gametes because of failure of separation in first meiotic metaphase
-Gametes end up (typically) with two copies of chromosome instead of one, or no copies of chromosome
-When two chromosome gamete combines with one chromosome gamete, Trisomy results
-When no chromosome gamete combines with one chromosome gamete, Monosomy results
Down Syndrome - symptoms, % distribution of nondisjunction cases, what is the recurrence rate of trisomy 21 related to, what recurrence rate of translocation
-Short stature, characteristic facial features, mental retardation, hypotonia, CV defects, leukemia, Alzheimer disease, premature death
-95% of cases-Trisomy 21- 4% Translocation-1% mosaicism
-Recurrence rate of trisomy 21 related to maternal age
-Recurrence Rate Of -Translocation Variant Much Higher ~1/3
-Trisomy 21 is a type of translocation
Down Syndrome vs. Maternal Age
-Less than 25 yrs = 1/2000 Incidence Rate
-35 yrs = 1/300
40 = 1/100
Doctor, what are the chances that we will have another child with Down syndrome?
-If Trisomy 21 (95%)
-Related to maternal age
-Definitive answer requires cytogenetics

-If Translocation Type (4%)
-About 1/3 if one parent is carrier (and father or mother)
-Definitive answer requires cytogenetics