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Which of the following is NOT a potential cause of clubfoot?
Which of the following is NOT a potential cause of clubfoot?
What is the primary characteristic of preeclampsia?
What is the primary characteristic of preeclampsia?
What is the potential origin of amniotic bands?
What is the potential origin of amniotic bands?
What is the potential consequence of amniotic bands?
What is the potential consequence of amniotic bands?
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What is the term for seizures that can develop as a complication of preeclampsia?
What is the term for seizures that can develop as a complication of preeclampsia?
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Which of the following is a trisomy of autosomes?
Which of the following is a trisomy of autosomes?
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Which of the following chromosomal abnormalities is characterized by a 47,XXY karyotype?
Which of the following chromosomal abnormalities is characterized by a 47,XXY karyotype?
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What is a common clinical feature associated with Klinefelter syndrome?
What is a common clinical feature associated with Klinefelter syndrome?
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An individual with a 47,XXX karyotype is most likely to have which condition?
An individual with a 47,XXX karyotype is most likely to have which condition?
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Which of the following is a monosomy compatible with life?
Which of the following is a monosomy compatible with life?
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Which syndrome is often associated with speech problems and low self-esteem in females?
Which syndrome is often associated with speech problems and low self-esteem in females?
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What is the most common cause of Triple X syndrome?
What is the most common cause of Triple X syndrome?
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Which of the following is a characteristic of Turner syndrome?
Which of the following is a characteristic of Turner syndrome?
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What is the immediate precursor to primordial germ cells?
What is the immediate precursor to primordial germ cells?
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During which week of development do primordial germ cells migrate from the yolk sac to the genital ridge?
During which week of development do primordial germ cells migrate from the yolk sac to the genital ridge?
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What is the ploidy of primordial germ cells upon their arrival at the genital ridge?
What is the ploidy of primordial germ cells upon their arrival at the genital ridge?
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What process do oogonia undergo to differentiate into mature oocytes?
What process do oogonia undergo to differentiate into mature oocytes?
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At which stage of meiosis are primary oocytes arrested before puberty?
At which stage of meiosis are primary oocytes arrested before puberty?
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What is the approximate range of primary oocytes present at birth?
What is the approximate range of primary oocytes present at birth?
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What happens to the majority of oogonia by the seventh month of development?
What happens to the majority of oogonia by the seventh month of development?
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What is the function of the flat follicular epithelial cells surrounding the primary oocyte?
What is the function of the flat follicular epithelial cells surrounding the primary oocyte?
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Which of the following cell types are directly adjacent to the cytotrophoblast and known as amnioblasts?
Which of the following cell types are directly adjacent to the cytotrophoblast and known as amnioblasts?
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What structure is formed by the migration of hypoblast cells, lining the blastocyst cavity?
What structure is formed by the migration of hypoblast cells, lining the blastocyst cavity?
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What is the name of the cavity formed after the blastocyst is lined by the exocoelomic membrane?
What is the name of the cavity formed after the blastocyst is lined by the exocoelomic membrane?
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Which of these is a glycoprotein produced by the syncytiotrophoblast?
Which of these is a glycoprotein produced by the syncytiotrophoblast?
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A low level of hCG in maternal blood may be an indicator of which of the following?
A low level of hCG in maternal blood may be an indicator of which of the following?
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What is a hydatidiform mole characterized by?
What is a hydatidiform mole characterized by?
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What is the term for malignant tumors of the trophoblast that can occur after pregnancy?
What is the term for malignant tumors of the trophoblast that can occur after pregnancy?
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Which of the following is an example of an oncofetal antigen?
Which of the following is an example of an oncofetal antigen?
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What is the condition called when the positioning of all organs is reversed in a mirror image arrangement?
What is the condition called when the positioning of all organs is reversed in a mirror image arrangement?
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During which week of development does gastrulation begin, making it a sensitive stage for teratogenic insults?
During which week of development does gastrulation begin, making it a sensitive stage for teratogenic insults?
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What condition can result from teratogenic insults during the third week of development, characterized by a small forebrain and merged lateral ventricles?
What condition can result from teratogenic insults during the third week of development, characterized by a small forebrain and merged lateral ventricles?
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Which cells are programmed to become primordial germ cells and migrate toward the yolk sac during the second week of development?
Which cells are programmed to become primordial germ cells and migrate toward the yolk sac during the second week of development?
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Which structure is primarily formed during neurulation from the lateral edges of the neural plate?
Which structure is primarily formed during neurulation from the lateral edges of the neural plate?
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In which region does fusion of the neural tube begin during the process of neurulation?
In which region does fusion of the neural tube begin during the process of neurulation?
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What type of cells do primordial germ cells become after migrating to the genital ridge during the fifth week?
What type of cells do primordial germ cells become after migrating to the genital ridge during the fifth week?
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What phase does the formation of the neural plate precede in embryonic development?
What phase does the formation of the neural plate precede in embryonic development?
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What is the functional unit of the placenta called?
What is the functional unit of the placenta called?
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Which statement about dizygotic twins is accurate?
Which statement about dizygotic twins is accurate?
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What happens during the splitting of the zygote at the bilaminar germ disc stage?
What happens during the splitting of the zygote at the bilaminar germ disc stage?
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What is a potential cause of vanishing twins?
What is a potential cause of vanishing twins?
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In monozygotic twins, what is a key characteristic?
In monozygotic twins, what is a key characteristic?
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Which of the following describes chorion laeve?
Which of the following describes chorion laeve?
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How do monozygotic twins develop when the zygote splits at the early blastocyst stage?
How do monozygotic twins develop when the zygote splits at the early blastocyst stage?
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What percentage of monozygotic twin cases involve splitting at the two-cell stage?
What percentage of monozygotic twin cases involve splitting at the two-cell stage?
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Study Notes
Review Block-1 Lectures, Fall Semester 2024
- Presented by Dr. Ismail Memon, MBBS, PhD, Saba University School of Medicine
- Topics covered include syndromes due to numerical chromosomal abnormalities, structural chromosome abnormalities, microdeletion syndromes, fragile X syndrome, primordial germ cells, gametogenesis, oogenesis, ovulation, zygote formation, cleavage and blastocyst formation, stages of human embryo development, blastocyst formation, end of 1st week, further development of the embryoblast, clinical considerations, oncofetal antigens, gastrulation, formation of the trilaminar embryonic disc, formation of primitive streak, functions of primitive streak, clinical correlates, limb defects, polydactyly, cleft hand and foot, arthrogryposis, amniotic bands, and preeclampsia.
Important Syndromes due to Numerical Chromosomal Abnormalities
-
Trisomy of Autosomes:
- Down Syndrome (Trisomy 21)
- Edwards Syndrome (Trisomy 18)
- Patau Syndrome (Trisomy 13)
-
Trisomy of Sex Chromosome:
- Klinefelter Syndrome (47, XXY)
- Triple X Syndrome (47, XXX)
-
Monosomy:
- Turner Syndrome (45, XO)
Klinefelter Syndrome
- Genetic condition in males
- Caused by an extra X chromosome
- Often diagnosed in adulthood
- Characterized by:
- Sterility
- Testicular atrophy
- Hyalinization of seminiferous tubules
- Long limbs
- Gynecomastia
Triple X Syndrome
- Affects about 1 in 1000 females
- Caused by an extra X chromosome
- Often asymptomatic or with mild symptoms
- May include:
- Scanty menses
- Mental retardation
Turner Syndrome
- Only monosomy compatible with life
- Characterized by:
- Absence of ovaries
- Short stature
- Other associated abnormalities (e.g., webbed neck, lymphedema)
- 98% of fetuses with this syndrome are spontaneously aborted
Cri-du-chat Syndrome
- Caused by partial deletion of the short arm of chromosome 5
- Characterized by:
- Cat-like cry
- Microcephaly
- Mental retardation
- Congenital heart disease
Microdeletion Syndromes
-
Angelman Syndrome:
- Deletion on the maternal chromosome 15
- Mental retardation, inability to speak, poor motor development, and unprovoked laughter.
-
Prader-Willi Syndrome:
- Deletion on the paternal chromosome 15
- Hypotonia, obesity, and mental retardation.
Fragile X Syndrome
- Caused by mutation in the FMR1 gene
- Characterized by:
- Mental retardation
- Large ears
- Prominent jaw
- Pale blue irises
- More severe in males due to having only one X chromosome
Primordial Germ Cells (PGCs)
- Precursors to sperm and eggs
- Generate new generations
- Mature into male or female germ cells
- Migrate to the genital ridge in the 5th week of development.
Gametogenesis and Oogenesis
- Sperm fertilizes egg to form Zygote
- Zygote develops into blastocyst
- Blastocyst implants in the endometrium of uterus
- Oogenesis starts before birth, then halts until puberty
- Oogonia develop into primary oocytes in the ovaries, arresting in prophase
- At puberty, oocytes resume and complete meiosis
- Primary oocytes remain arrested in Prophase 1 until ovulation
- The majority of oogonia degenerate by the 7th month of gestation
Ovulation
- At puberty, 15-20 follicles mature each month.
- These follicles contain oocytes in various development stages (primordial, primary, secondary, vesicular)
- These follicles are stimulated to grow under the influence of FSH.
- Oocyte maturation is regulated by the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
Clinical Considerations
-
Human Chorionic Gonadotropin (hCG):
- Glycoprotein produced by syncytiotrophoblast
- Stimulates progesterone production by corpus luteum
- Basis for pregnancy testing
- Low levels can suggest spontaneous abortion or ectopic pregnancy, high levels may suggest multiple pregnancy, hydatidiform mole, or gestational trophoblastic neoplasia.
-
Gestational Trophoblastic Disease:
- Hydatidiform mole: benign, grape-like vesicles in uterus.
- Choriocarcinoma: malignant tumor of trophoblast, may occur after an aborted pregnancy or normal pregnancy
- Oncofetal antigens: Cell surface antigens that are elevated in certain cancers
Gastrulation
- Conversion of bilaminar disc into trilaminar embryonic disc (ectoderm, mesoderm, endoderm)
- Formation of the primitive streak
- Epiblast cells differentiate and migrate to form endoderm and mesoderm
Neural Tube Formation
- Neural plate forms the neural tube
- Completion of neurulation involves the fusion of neural folds
- Neural tube defects result when neural tube closure fails leading to defects like spina bifida and anencephaly
Placenta
- Temporary pregnancy organ that provides nutrients and oxygen to the fetus through the umbilical cord
- Has maternal (decidua) and fetal (chorion frondosum) parts
- Formed by the proliferation of chorionic villi
Twinning
- Dizygotic (fraternal): Fertilization of two different secondary oocytes by two different sperms (usually 90% of twins).
- Monozygotic (identical): Zygote splits at various stages of development (usually 10% of twins).
Limb Defects
- Amelia: Absence of one or more limbs
- Meromelia: Partial absence of limbs
- Micromelism: Abnormally short limbs
- Brachydactyly: Shortened digits
- Syndactyly: Fused digits
- Cleft hand/foot: Cleft between the second and fourth metacarpal or metatarsal bones
- Arthrogryposis: Congenital joint contractures
- Amniotic Bands: Ring constrictions and amputations of limbs
Preeclampsia
- Leading cause of maternal mortality
- Condition characterized by maternal hypertension and proteinuria
- Occurs in approximately 5% of pregnancies
- Can have various complications such as reduced organ perfusion
Other
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Description
Test your knowledge on medical genetics with this quiz focusing on chromosomal disorders such as trisomy and monosomy, as well as the associated syndromes. Explore key concepts related to clubfoot, preeclampsia, and Turner syndrome among others. Perfect for those studying genetics or preparing for medical exams.
