Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
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...
|
-zygote
|
|
|
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
|
-10^8/day
-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 |
|
|
STUDY SLIDES 15 & 16
|
STUDY SLIDES 15 & 16
|
|
|
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 |
