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These 10 free ELD questions are organized by exam domain, so you can see how each part of the Embryology Laboratory Director blueprint is tested. Reveal the answer and explanation under each question.
During a routine incubator check, an embryologist increases the CO2 set-point from 6.0% to 7.0% while the medium and its bicarbonate concentration stay the same. What is the expected effect on the pH of the bicarbonate-buffered culture medium?
Correct answer: A - The pH falls, becoming more acidic
A laboratory transitions its blastocyst culture from atmospheric oxygen to a tri-gas incubator. Which oxygen concentration is generally recommended to support blastocyst development, and why?
Correct answer: C - About 5%, approximating the oviductal environment and limiting oxidative stress
Before releasing a new lot of embryo culture medium for clinical use, a director wants a bioassay that reflects the medium's actual ability to support development. Which quality-control test is designed for this purpose?
Correct answer: A - The mouse embryo assay (MEA) measuring blastocyst development
An embryo is recorded as a '4AA' blastocyst using the Gardner grading system. What does the numeral '4' specifically describe?
Correct answer: B - The degree of blastocoel expansion
A patient's embryos are placed in extended culture so trophectoderm biopsy for PGT can be performed at the blastocyst stage. On approximately which day of in-vitro development does a human embryo typically reach the full blastocyst stage suitable for biopsy?
Correct answer: D - Day 5 to Day 6, at the expanded blastocyst stage
A patient responds strongly to ovarian stimulation with a very high estradiol level and numerous follicles. The team elects a 'freeze-all' approach, cryopreserving every embryo for a later frozen transfer. What is the PRIMARY clinical rationale for this decision?
Correct answer: A - Deferring transfer lowers the risk of ovarian hyperstimulation syndrome
At the fertilization check after conventional (non-ICSI) insemination, an oocyte displays three distinct pronuclei. How should this observation be interpreted?
Correct answer: D - Abnormal fertilization, most consistent with polyspermy
A laboratory adopts vitrification for blastocyst cryopreservation. Which statement best describes how vitrification differs from conventional slow-rate freezing?
Correct answer: B - It uses ultra-rapid cooling with high cryoprotectant levels to prevent ice crystals
In a vitrification solution, sucrose and trehalose serve a specific protective role. These agents are classified as:
Correct answer: D - Non-permeating cryoprotectants that draw water out osmotically
After denudation, an oocyte shows no germinal vesicle and a clearly extruded first polar body in the perivitelline space. What is the maturation stage of this oocyte?
Correct answer: A - Metaphase II (MII)
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