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TAMU ANSC 333 Exam 4 Questions & answers
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TAMU ANSC 333 Exam 4the recombination of the paternal and maternal chromatin. - ANS-Syngamy
syngamy occurs after completion of DNA replication. - ANS-When does syngamy
occur?
Cytoskeletal components - ANS-Syngamy is mediated by?
a single celled embryo that has not underwent syngamy. - ANS-Define: Zygote
oviduct - ANS-Embryonic development begins within the _______.
DNA replication through multiple mitotic divisions, however there is no cytokinesis or
excess cytoplasmic production. The cells undergo capacitation - ANS-What occurs
within the oviduct in early embryonic development?
cells replicate, however the zona pellucida does not grow in size, the cells become
smaller and smaller within the Zona. - ANS-In early embryonic development, what
occurs within the cells within the *zona pellucida* as a cell goes from a single cell
zygote, to 2 cell embryo, 4 cell embryo, etc.
When an embryo has undergone enough mitotic divisions and individual cells can no
longer be counted - ANS-Define: Morula
compacted morula - ANS-An embryo transforms from a 32 cell embryonic stage to a
_________ ________.
totipotent - ANS-Every cell within the embryo is considered _________, *up until the
point of compaction.*
cell that can make any "decision" they want to become anything. They have not made
their functional decisions yet. - ANS-Define: totipotent
Cells in the middle of the embryo form gap junctions between themselves. Their cells on
the outside, form tight junctions with each other. This is the first decision the cells make.
Once they have made their decision, the are now pluripotent. - ANS-Describe what
happens during compaction:
,if the cell forms a tight or gap junction. - ANS-How can one determined what type of cell
function an embryonic cell will have?
fetal cell - ANS-If a totipotent cell forms a *gap* junction, it will become a ? and form the
*inner cell mass*.
placental cell - ANS-If a totipotent cell forms a *tight* junction, it will become a ?
trophoblast cells - ANS-What cells are on the exterior of the tight junctions?
Trophoblast cells, on the exterior of tight junctions, have Na+ transporters. These cause
water to be pumped into the cell and water accumulates. Trophoblasts form the
*blastocoel*, which is a water filled cavity. This means the cell is no longer a morula it a
*blastocyst.* - ANS-Describe trophoblasts and what they do:
day 4-5 of pregnancy - ANS-When does the blastocyst enter the uterus, from the
oviduct?
The rupturing of the Zona pellucida due to the expansion of an *expanded blastocyst*
within the trophoblast layer, which lines the Zona pellucida. The Zona Pellucida is
stretched and ruptures. - ANS-What is hatching?
stage of the embryo
location of the embryo
What time to do the technology - ANS-When incorporating assisted reproductive
technologies, it is important to know what factors?
Day 7 of pregnancy - ANS-When is embryo transfer done is cattle?
Day 6 of pregnancy - ANS-When is embryo transfer done in sheep?
biologically it *is* possible, however it is more invasive given the embryo is still within
the oviduct. A major operation is less practical. - ANS-Why is it *logistically* a poor
decision to do an early embryo transfer before day 7 in cattle?
Waiting for compaction is the most cost efficient method. The cells are in the uterus at
this point and developed enough for flushing. You cannot flush from the oviduct then
implant into the recipient because they must be placed where they were in the donor
female for proper development to continue. - ANS-What is the best way to save money
on recipient females?
, 10 of pregnancy - ANS-*biologically* you can flush on day ?
day 15 of pregnancy - ANS-What day is attachment to the uterus in sheep?
Day 17 of Pregnancy - ANS-What day is attachment to the uterus in cows?
Pregnancy rates decrease by 10% once the embryo has attached to the uterus. This is
*because* of the higher development, and the lack of zona pellucida, which is the
embryos protection. There is risk of physiological damage from pipettes and straws. -
ANS-Pregnancy rates *decrease* by _____%, if you wait for the embryo to be hatched.
Why?
True! - ANS-T/F: There is a window of time where the embryo is in the uterus, still
encased in the zona pellucida, and it is optimally developed to the blastocyst or
compacted morula.
the percentage of cells that are *alive and viable*. - ANS-Embryos are staged and
graded. What is the *grade* based on?
only one cell replicates continually, this means *viability of the embryo is 50%.* -
ANS-What happens if a cell dies before its first division?
It is unethical to remove a human embryo from a woman and assess the developmental
stages. - ANS-Why is early embryonic development less studied in people? (and rats
are used)
development continues, and implantation is initiated. - ANS-What occurs *after
hatching* of the fetus?
the act of actual and physical *attachment* of the embryo to the uterus - ANS-define:
implantation
livestock species attach to the lumen, while primates penetrate and burrow into the
endometrium. - ANS-How does attachment differ between livestock species and
primates?
all embryos are developing at different stages - ANS-Why is super-ovulation difficult to
study?
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