Gametogenesis I Flashcards
define determination
process by which a cell becomes restricted to a given development pathway
define differentiation
complex of changes involved in progressive specialization of structure and function
hyperplasia
increase in cell number
hypertrophy
increase in cell size
define morphogenesis
generation of form or assumption of new shape
define induction
an effect one embryonic tissue has upon another
such that development course in qualitatively changed from what it would have been w/o the inducer
define integration
process in which dif tissues are brought together to form organs and tissues
define gametogenesis
generation and development of gametes – sperm cells and oocytes
phases of gametogenesis
- migration to gonads
- increase in germ cell # via mitosis
- reduction in chromosomal # via meiosis
- maturation of eggs and spermatozoa
following fertilization, when do the primordial germ cells first appear?
24 days after fertilization
found in endodermal layer of yolk sac
trace the migration route of primordial germ cells into the developing gonads from the yolk sac
yolk sac
hindgut epithelium
thru dorsal mesentery
into developing gonads
define teratoma
growths from misdirected migrating primordial germ cells
contain mixture of dif tissues
mass of cells w/o axis
list the stages of prophase I
leptotene zygotene pachytene diplotene diakinesis
leptotene
chromosomes are threadlike
- consist of 2 chromatids
- begin to coil
zygotene
homologous chromosomes pair = synapsis
forming synaptonemal complex
pachytene
max coiling achieved
tetrads
crossing over begins
diplotene
cross-over continues and chiasmata are well defined
diakinesis
crossing over is completed
terminalization
spindle apparatus is in place
nuclear memb disrupted
metaphase I
tetrads line up along equatorial plate
centromeres do not divide
anaphase I
homologous chromosomes move to opposite poles
not identical due to crossing over
daughters will be haploid
telophase I
cytokinesis occurs
nuclear memb. reforms
spindle apparatus disassembles and chromosomes may uncoil
prophase II
chromosomes recondense
- -nuclear memb disappears
- -spindle apparatus forms
metaphase II
chromosomes line up at equator
anaphase II
centromeres divide
chromosomes move to opposite poles
–each consisting of a single chromatid
telophase II
chromosomes uncoil
cytokinesis complete
nuclear memb formed
end result of meiosis
4 genetically unique haploid daughter cells
major events in meiosis
- pairing of homologous chr = synapsis
- crossing over
- 2 rounds of division but only 1 round of DNA replication
major results of meiosis
- increase in cell #
- daughters are not identical
- daughters are haploid
somatic vs germ cells
nonreproductive body cells
reproductive haploid cells
define aneuploidy
abnormal number of chromosomes
monosomy, trisomy
changes that can occur in parts of chromosomes
translocations
deletions
inversions
duplications
define euploidy
changes in number of complete sets of chromosomes
monoploidy/haploidy = 1 set diploidy = 2 polyploidy = >2 sets
compare total number of oocytes present from embryo to puberty
7 mil - embryonic midterm
2 mil - birth
400k soon after birth
40k puberty
~400-450 actually ovulated thru life
destiny for primary oocytes
~400 will be ovulated
out of 40k
the rest will become atretic and die
follicular structure — fetal period
oogonia not surround by follicular cells
no follicle
1 chr/cell
follicular structure – late fetal period to birth
oocyte arrested at diplotene
primordial follicle formed w/ flat follicle cells
2 chr/cell
follicular structure - birth to puberty
diploid oocyte
primary follicle w/ 1 layer cube follicular cells
-zona pellucida separates oocyte from follicular cells
2 chr/cell
what connects oocytes and follicle cells
microvilli and gap junctions
oocyte during ovulation
proceeds to metaphase II
- -2ndary follicle w/ several layers of cells
- -beginning of antrum formation
2 chr/cell
the membrane granulosa surrounds?
outside of follicle cells
tertiary follicle formation
forms near end of ovulation
multiple layers of cells
corona radiata
large antrum
mural granulosa cells
cells between memb granulosa and antrum
cumulus cells
cells between zona pellucida and antrum
prior to ovulation the haploid secondary oocyte is with ?
corona radiata
thecal cells
polar body
prior to ovulation granulosa cells will develop?
FSH and LH receptors
circulating FSH stims granulosa cells to produce estrogen
why is meiosis arrested at metaphase II in oocytes
due to LH surge
which shuts down gap junctions between granulosa cells and oocyte
cAMP reduced
allows activation of MPF
ended at tertiary follicle slide 33
slide 33
