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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}} {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Physiology
|MainCategory=Physiology
Line 20: Line 20:
|MainCategory=Physiology
|MainCategory=Physiology
|SubCategory=Reproductive
|SubCategory=Reproductive
|Prompt=A researcher studying the process of ovulation in human females recruits 10 female volunteers. He injects subcutaneously human chorionic gonadotropin (HCG) hormone and retrieves the eggs 35 hours later. Using appropriate technique, he visualizes the eggs under fluorescence microscopy. Under fluorescence microscopy, which of the following observations does the researcher most likely make?
|Prompt=A researcher studying the process of ovulation in human females recruits 10 female volunteers. He injects subcutaneously human chorionic gonadotropin (HCG) hormone and retrieves the eggs 35 hours later. Using the appropriate technique, he views the eggs under fluorescence microscopy. Under fluorescence microscopy, which of the following observations does the researcher most likely make?
|Explanation=The process described above is induction of ovulation, whereby patients typically receive subcutaneous injections of HCG (mimicker of LH) followed by egg retrieval 35-40 hours later. In this process, ovulation is most likely to have occurred and retrieval of oocytes is then made possible. Normally in a human female, oocytes are arrested after ovulation at metaphase II before fertilization takes place. Only if fertilization ever happens, the oocyte should presume meiosis II. Under fluorescence microscopy, metaphase II is characterized by the presence of sister chromatids along the equatorial plate. In contrast, metaphase I is characterized by the presence of homologous chromosomes along the equatorial plate. Remarkably, different species have their oocytes at different stages of meiosis.  
|Explanation=The process described above is induction of ovulation, whereby patients typically receive subcutaneous injections of HCG (a mimicker of LH) followed by egg retrieval 35-40 hours later. In this process, ovulation is most likely occurs and retrieval of oocytes is then made possible. Typically in females, following ovulation, oocytes are arrested at metaphase II, before fertilization takes place. Only if fertilization occurs, will the oocyte presume meiosis II. Under fluorescence microscopy, metaphase II is characterized by the presence of sister chromatids along the equatorial plate. In contrast, metaphase I is characterized by the presence of homologous chromosomes along the equatorial plate. Different species produce oocytes at different stages of meiosis.  
 
|EducationalObjectives= Meiosis of human oocytes is arrested at metaphase II following ovulation. Metaphase II is characterized by the presence of sister chromatids along the equatorial plate.
|References= First Aid 2014 page 569


|EducationalObjectives=
Meiosis of human oocytes is arrested at metaphase II after ovulation. Metaphase II is characterized by the presence of sister chromatids along the equatorial plate.
|AnswerA=Beginning of the disappearance of the nuclear envelope
|AnswerA=Beginning of the disappearance of the nuclear envelope
|AnswerAExp=Early prophase I is characterized by the disappearance of the nuclear envelope.
|AnswerAExp=Early prophase I is characterized by the disappearance of the nuclear envelope.
|AnswerB=Alignment of the sister chromatids on the equatorial plate.
|AnswerB=Alignment of the sister chromatids on the equatorial plate.
|AnswerBExp=Alignment of the sister chromatids on the equatorial plate is seen in metaphase II, which is the step that oocyte arrest at after ovulation before fertilization.
|AnswerBExp=Alignment of the sister chromatids on the equatorial plate occurs during metaphase II, the step where oocyte arrest takes place, following ovulation and before fertilization.
|AnswerC=Alignment of the homologous chromosomes on the equatorial plate
|AnswerC=Alignment of the homologous chromosomes on the equatorial plate
|AnswerCExp=Alignment of the homologous chromosomes on the equatorial plate is seen in metaphase I.
|AnswerCExp=Alignment of the homologous chromosomes on the equatorial plate occurs during metaphase I.
|AnswerD=Movement of sister chromatids to opposite poles
|AnswerD=Movement of sister chromatids to opposite poles
|AnswerDExp=Movement of sister chromatids to opposite poles is seen in anaphase II.
|AnswerDExp=Movement of sister chromatids to opposite poles occurs during anaphase II.
|AnswerE=Movement of homologous chromosomes to opposite poles
|AnswerE=Movement of homologous chromosomes to opposite poles
|AnswerEExp=Movement of homologous chromosomes to opposite poles is seen in anaphase I.
|AnswerEExp=Movement of homologous chromosomes to opposite poles occurs during anaphase I.
|RightAnswer=B
|RightAnswer=B
|WBRKeyword=metaphase, I, II, anaphase, prophase, telophase, meiosis, oocyte, egg, HCG, human, chorionic gonadotropin, ovulation, fertilization, fluorescent, fluorescence, microscope, microscopy
|WBRKeyword=metaphase I, metaphase II, anaphase, prophase, telophase, meiosis, oocyte, egg, HCG, human, chorionic gonadotropin, ovulation, fertilization, fluorescence microscopy
|Approved=No
|Approved=Yes
}}
}}

Revision as of 13:09, 15 July 2014
Author [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Physiology
Sub Category SubCategory::Reproductive
Prompt [[Prompt::A researcher studying the process of ovulation in human females recruits 10 female volunteers. He injects subcutaneously human chorionic gonadotropin (HCG) hormone and retrieves the eggs 35 hours later. Using the appropriate technique, he views the eggs under fluorescence microscopy. Under fluorescence microscopy, which of the following observations does the researcher most likely make?]]
Answer A AnswerA::Beginning of the disappearance of the nuclear envelope
Answer A Explanation AnswerAExp::Early prophase I is characterized by the disappearance of the nuclear envelope.
Answer B AnswerB::Alignment of the sister chromatids on the equatorial plate.
Answer B Explanation AnswerBExp::Alignment of the sister chromatids on the equatorial plate occurs during metaphase II, the step where oocyte arrest takes place, following ovulation and before fertilization.
Answer C AnswerC::Alignment of the homologous chromosomes on the equatorial plate
Answer C Explanation AnswerCExp::Alignment of the homologous chromosomes on the equatorial plate occurs during metaphase I.
Answer D AnswerD::Movement of sister chromatids to opposite poles
Answer D Explanation AnswerDExp::Movement of sister chromatids to opposite poles occurs during anaphase II.
Answer E AnswerE::Movement of homologous chromosomes to opposite poles
Answer E Explanation AnswerEExp::Movement of homologous chromosomes to opposite poles occurs during anaphase I.
Right Answer RightAnswer::B
Explanation [[Explanation::The process described above is induction of ovulation, whereby patients typically receive subcutaneous injections of HCG (a mimicker of LH) followed by egg retrieval 35-40 hours later. In this process, ovulation is most likely occurs and retrieval of oocytes is then made possible. Typically in females, following ovulation, oocytes are arrested at metaphase II, before fertilization takes place. Only if fertilization occurs, will the oocyte presume meiosis II. Under fluorescence microscopy, metaphase II is characterized by the presence of sister chromatids along the equatorial plate. In contrast, metaphase I is characterized by the presence of homologous chromosomes along the equatorial plate. Different species produce oocytes at different stages of meiosis.

Educational Objective: Meiosis of human oocytes is arrested at metaphase II following ovulation. Metaphase II is characterized by the presence of sister chromatids along the equatorial plate.
References: First Aid 2014 page 569]]

Approved Approved::Yes
Keyword WBRKeyword::metaphase I, WBRKeyword::metaphase II, WBRKeyword::anaphase, WBRKeyword::prophase, WBRKeyword::telophase, WBRKeyword::meiosis, WBRKeyword::oocyte, WBRKeyword::egg, WBRKeyword::HCG, WBRKeyword::human, WBRKeyword::chorionic gonadotropin, WBRKeyword::ovulation, WBRKeyword::fertilization, WBRKeyword::fluorescence microscopy
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