lecture 4 germline 1 Flashcards
down syndrome is
trisomy 21
XXY
klinefelter syndrome
turner syndrome
XO
these cells pass genetic information from one generation to the next
germ cells
__ is made from RNA binding proteins involved in translational control
Germ plasm
name two types of RNA binding proteins used by germ plasm
VASA, Tudor
in frogs, germ plasm is found in
the vegetal pole cytoplasm
in flies, germ plasm is characterized by
polar granules in fertilized eggs
in mammals, ___ are released by extra-embryonic tissue into the border of the epiblast and stimulate the change of cells into PCG precursor cells
BMP
BMP stands for
bone morphogenetic protein
common BMP factors in mice
BMP-4 and BMP-86
if germ plasm in frogs is irradiated, what happens to germ cells?
germ cells will not be produced
what are the three steps of PGC specification
- repression of somatic programs
- re-aquisition of potential pluripotency
- genome-wide epigenetic reprogramming
what are expressed by PGCs
Prdm
what does Prdm stand for
PR-domain containing transcription factors
What helps with the last two steps of PGC specifications
- re-aquisition of potential pluripotency
- genome-wide epigenetic reprogramming
Prdm 14
What TF helps with all three steps of PGC specifications
Prdm 1
- repression of somatic programs
- re-aquisition of potential pluripotency
- genome-wide epigenetic reprogramming
what are some non functional markers expressed by PGCs
TNAP- tissue non-specific alkaline phosphate
Fragilis
Stella
what is the migration of PGCs
border of epiblast extra-embryonic mesoderm base of allantois move around hindgut through dorsal mesentery genital ridges
once PGCs express ___ and ___ their fate is ___
Prdm1 and Prdm14
determined- can’t change into other cells
PGCs proliferate from ___ cells to ___ cells. This happens around day ___ in mice
45
20,000
E 11.5
Migration of PGCs are helped by ___ such as ___ produced by ___
chemokine factor
Sdf1
surrounding tissues
Sdf1 is
stromal cell-derived factor 1
___ is a ____ receptor on ___ that attaches to Sdf1
Cxcr4
chemokine
PGC
___ is a receptor for steel factor and is expressed by ____
c-Kit
PGCs
___ is a cell surface molecule on PGCs
beta1 integrin
Steel + W is __ and leads to ___ by interfering with ___
dominant white spotting
sterility, anemia and white coat
PCG survival, proliferation and migration
Steel factor (SI) is the product of the ___ locus and the ligand for ____
steel
c-Kit
___ is a tyrosine kinase receptor and is a product of the ___ locus
c-kit
W
gonad differentiation occurs at day ___ in mice
E12.5
___ is the sex determining gene from Y. Produced day ___
Sry expression
E10.5-11.5
before day ___ germ cells are bipotential meaning ____
12.5
they can become male or female
___ is the enzyme that degrades retinoic acid
CYP26B1
In testes. CYP26B1 is ___ then there is ___ RA and Stra8 is ___ which will ___ meiosis.
on
decreased
off
stop
In ovaries. CYP26B1 is ___ then there is ___ RA and Stra8 is ___ which will ___ meiosis.
off
increased
on
start meiosis
if stra8 is on then ___
meiosis starts
__ are mother cells that help spem production
sertoli cells
what are the 4 stages of prophase
leptotene
zygotene
pachytene
diplotene
meiosis steps
PMAT 1 and PMAT 2 P- homologous pairs (male and female) match up and cross over happens M- homologous pairs line up A- homologous pairs are pulled apart T- two cells are formed by cytokinesis
P- chromosomes condense
M- sister chromatids line up in center
A- sister chromatids are divided
T- 4 haploid (1N, 1 C) unique cells
reciprocal exchange of genetic material between homologous pairs
meiotic recombination
two ways meiosis 1 is different from mitosis
recombination of homologous pairs
segregation of homologous pairs
what happens in leptotene phase and what step is it
chromosomes begin to condense and become visible as long threadlike structures
step 1 of prophase 1
what happens in zygotene phase and what step is it
partial synapsis
SYCP1 only located on synapsed regions but not on unsynapsed regions
step 2 of prophase 1
what happens in pachytene phase and what step is it
cross over between homologous chromosomes, complete synapsis
step 3 of prophase 1
what happens in diplotene phase and what step is it
synapsis starts to break away but held together by chiasmata
step 4 of prophase 1
site of recombination
chiasmata
what stage is the first meiosis stop in females and when does it stop
Diplotene phase (step 4 of prophase 1) stops before fetus is born
when does meiosis restart for females
before ovulation at puberty increase levels of FSH (follicle stimulating hormone) triggers the completion of meiosis 1 creating a polar body and secondary oocyte (daughter cell). Meiosis 2 is stopped at Metaphase 2
when does the 2nd meiosis restart for females
at fertilization. when sperm enters egg, meiosis 2 restarts and creates polar body and daughter cell.
what phase is a dog oocyte in when ovulated and how is it different then humans
dog oocyte at prophase I when ovulated, humans oocyte ovulated at Metaphase II
what are some differences between oogenesis and spermatogenesis
oogenesis
- limited number
- meiosis stops twice
- only 1 gamete(oocyte produced)
- differentiation of gamete occurs before completion of meiosis
Spermatogenesis
- unlimited number due to spermatogonial stem cells
- meiosis starts at puberty and is continuous
- 4 sperm produced
- differentiation while haploid
___ are cells that produce testosterone
interstitial Leydig cells
___ is where spermatogenesis occurs
seminiferous tubules
briefly explain spermatogenesis
PGC + Sry expression CYB26B1 on spermatogonia- mitotic division primary spermatocyte- meiosis I 2- secondary spermatocyte- meiosis II 4- spermatid- (haploid) residual body leaves 4- spermatozoa
briefly explain oogenesis
PGC CYB26B1 off
OOGONIA- enters meiosis I stops at diplotene prophase- follicle cells become granulosa cells
PRIMARY OOCYTE- granulosa cells fatten
PRIMARY FOLLICLE- Puberty hits, FSH stimulates many layers of granulosa
SECONDARY FOLLICLE- antrum , ZP and cumulus oophorus form
TERTIARY FOLLICLE- cell restarts Meiosis I creating daughter and polar body- stops at Metaphase II- cell is ovulated *breaks out of follicle- still within ZP
SECONDARY OOCYTE- stays in Metaphase II until fertilization- completes Meiosis II creates oocyte and polar body. That oocyte then ready to combine with sperm and do mitosis.
mules have an odd number of chromosome which means ___ can’t happen. this is called ___.
meiosis
hybrid sterility
