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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor= {{YD}} (Reviewed by  {{YD}} and  {{AJL}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Physiology
|MainCategory=Physiology
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|MainCategory=Physiology
|MainCategory=Physiology
|SubCategory=Reproductive
|SubCategory=Reproductive
|MainCategory=Physiology
|MainCategory=Physiology
|MainCategory=Physiology
|MainCategory=Physiology
|MainCategory=Physiology
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|MainCategory=Physiology
|MainCategory=Physiology
|SubCategory=Reproductive
|SubCategory=Reproductive
|Prompt=A researcher is studying the process of ovulation in human females. For the purpose of his experiment, he 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. What is the most likely observation under fluorescence microscopy will the researcher find?
|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 findings does the researcher most likely observe?
|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 most likely occurs, and retrieval of oocytes is then made possible. Typically in females, cell division of oocytes is arrested at metaphase II following ovulation and prior to fertilization. Only if fertilization occurs, will the oocyte resume 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. Unlike humans, other species may produce oocytes at different stages of meiosis.<br>


Educational Objective:  
[[Image:Mitosis Meiosis Ovulation Fertilization Cell Cycle Arrest Chromosome Haploid Diploid Oogonium Ovum Oocyte Figure.png|1000px]]
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 along 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 along the equatorial plate occurs during metaphase II, the stage where oocyte arrest takes place following ovulation and prior to fertilization.
|AnswerC=Alignment of the homologous chromosomes on the equatorial plate
|AnswerC=Alignment of the homologous chromosomes along the equatorial plate
|AnswerCExp=Alignment of the homologous chromosomes on the equatorial plate is seen in metaphase I.
|AnswerCExp=Alignment of the homologous chromosomes along the equatorial plate occurs during metaphase I.
|AnswerD=Movement of sister chromatids to opposite poles
|AnswerD=Migration of sister chromatids to opposite poles
|AnswerDExp=Movement of sister chromatids to opposite poles is seen in anaphase II.
|AnswerDExp=Migration of sister chromatids to opposite poles occurs during anaphase II.
|AnswerE=Movement of homologous chromosomes to opposite poles
|AnswerE=Migration of homologous chromosomes to opposite poles
|AnswerEExp=Movement of homologous chromosomes to opposite poles is seen in anaphase I.
|AnswerEExp=Migration of homologous chromosomes to opposite poles occurs during anaphase I.
|EducationalObjectives=Following ovulation, meiosis of human oocytes is arrested at metaphase II, which is a phase of cell division characterized by the presence of sister chromatids along the equatorial plate.
|References=First Aid 2014 page 569
|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, Oocyte, Egg, HCG, Human chorionic gonadotropin, Meiosis, Ovulation, Fertilization, Fluorescence microscopy
|Approved=No
|Approved=Yes
}}
}}

Latest revision as of 00:13, 28 October 2020
Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D. and Alison Leibowitz [1])]]
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 findings does the researcher most likely observe?]]
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 along the equatorial plate.
Answer B Explanation AnswerBExp::Alignment of the sister chromatids along the equatorial plate occurs during metaphase II, the stage where oocyte arrest takes place following ovulation and prior to fertilization.
Answer C AnswerC::Alignment of the homologous chromosomes along the equatorial plate
Answer C Explanation AnswerCExp::Alignment of the homologous chromosomes along the equatorial plate occurs during metaphase I.
Answer D AnswerD::Migration of sister chromatids to opposite poles
Answer D Explanation AnswerDExp::Migration of sister chromatids to opposite poles occurs during anaphase II.
Answer E AnswerE::Migration of homologous chromosomes to opposite poles
Answer E Explanation AnswerEExp::Migration 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 most likely occurs, and retrieval of oocytes is then made possible. Typically in females, cell division of oocytes is arrested at metaphase II following ovulation and prior to fertilization. Only if fertilization occurs, will the oocyte resume 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. Unlike humans, other species may produce oocytes at different stages of meiosis.


Educational Objective: Following ovulation, meiosis of human oocytes is arrested at metaphase II, which is a phase of cell division 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::Oocyte, WBRKeyword::Egg, WBRKeyword::HCG, WBRKeyword::Human chorionic gonadotropin, WBRKeyword::Meiosis, WBRKeyword::Ovulation, WBRKeyword::Fertilization, WBRKeyword::Fluorescence microscopy
Linked Question Linked::
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