Podcast
Questions and Answers
Which of the following is NOT a direct result of fertilization?
Which of the following is NOT a direct result of fertilization?
The decidua basalis contributes to which part of the placenta?
The decidua basalis contributes to which part of the placenta?
Failure of the caudal neuropore to close during neurulation results in?
Failure of the caudal neuropore to close during neurulation results in?
Monozygotic twins can result in which of the following?
Monozygotic twins can result in which of the following?
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Complete absence of limbs is referred to as:
Complete absence of limbs is referred to as:
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Which of the following chromosomal abnormalities is characterized by the karyotype 47, XXY?
Which of the following chromosomal abnormalities is characterized by the karyotype 47, XXY?
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A patient presents with short stature, a webbed neck, and the absence of ovaries. Which of the following conditions is most likely?
A patient presents with short stature, a webbed neck, and the absence of ovaries. Which of the following conditions is most likely?
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Which syndrome is associated with a deletion on the maternal chromosome 15?
Which syndrome is associated with a deletion on the maternal chromosome 15?
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Which of the following features is NOT a typical presentation of Klinefelter Syndrome?
Which of the following features is NOT a typical presentation of Klinefelter Syndrome?
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In oogenesis, at which stage do primary oocytes arrest until puberty?
In oogenesis, at which stage do primary oocytes arrest until puberty?
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Which of the following is a characteristic feature of Cri-du-chat Syndrome?
Which of the following is a characteristic feature of Cri-du-chat Syndrome?
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Prader-Willi syndrome is due to a microdeletion on which chromosome?
Prader-Willi syndrome is due to a microdeletion on which chromosome?
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Which of the following genetic conditions is caused by a mutation in the FMR1 gene?
Which of the following genetic conditions is caused by a mutation in the FMR1 gene?
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Study Notes
Chromosomal Abnormalities
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Numerical Abnormalities:
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Autosomal Trisomies:
- Trisomy 21 (Down Syndrome)
- Trisomy 18 (Edwards Syndrome)
- Trisomy 13 (Patau Syndrome)
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Sex Chromosome Trisomies:
- Klinefelter Syndrome (47, XXY)
- Triple X Syndrome (47, XXX)
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Monosomy:
- Turner Syndrome (45, XO)
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Autosomal Trisomies:
Syndromes in Detail
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Klinefelter Syndrome:
- Cause: Extra X chromosome (47, XXY).
- Features: Sterility, testicular atrophy, gynecomastia, long limbs.
- Diagnosis: Often detected through amniocentesis.
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Triple X Syndrome:
- Cause: Extra X chromosome (47, XXX).
- Features: Infertility, scanty menstruation, mild mental retardation; speech and self-esteem problems.
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Turner Syndrome:
- Karyotype: 45, X (only monosomy compatible with life).
- Features: Short stature, absence of ovaries, webbed neck, lymphedema, broad chest, widely spaced nipples.
Structural Chromosome Abnormalities
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Cri-du-chat Syndrome:
- Cause: Partial deletion of the short arm of chromosome 5.
- Features: Cat-like cry, microcephaly, congenital heart disease.
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Microdeletion Syndromes:
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Angelman Syndrome:
- Cause: Microdeletion on maternal chromosome 15.
- Features: Severe mental retardation, poor motor development, unprovoked laughter.
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Prader-Willi Syndrome:
- Cause: Microdeletion on paternal chromosome 15.
- Features: Hypotonia, obesity, mental retardation, hypogonadism.
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Angelman Syndrome:
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Fragile X Syndrome:
- Cause: Mutation in FMR1 gene.
- Features: Mental retardation, large ears, prominent jaw, pale blue irises.
Primordial Germ Cells and Gametogenesis
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Primordial Germ Cells (PGCs): Precursors to sperm and eggs, migrate from yolk sac to genital ridge by week 5.
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Oogenesis: Begins before birth, primary oocytes arrest in prophase I until puberty; 15–20 follicles mature each cycle, only one completes ovulation.
Fertilization
- Fertilization results in a zygote, restoring the diploid chromosome number (46), determining the sex, and initiating zygote cleavage.
Blastocyst Formation and Implantation
- Zygote → Morula → Blastocyst
- Blastocyst structure: Inner cell mass (embryoblast), outer cell mass (trophoblast), fluid-filled cavity (blastocele).
- Implantation occurs after blastocyst hatches from zona pellucida.
Placenta
- Maternal Part: Derived from decidua basalis.
- Fetal Part: Derived from chorion frondosum.
Neurulation
- Formation of neural tube from neural plate.
- Defects: Anencephaly (failure of cranial neuropore closure) and spina bifida (failure of caudal neuropore closure).
Twinning
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Dizygotic Twins: Two eggs, two sperms, two placentas, two amnions.
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Monozygotic Twins: One egg, one sperm, may share placenta, amnion, or both.
Limb Defects
- Amelia: Complete absence of limbs.
- Meromelia: Partial absence of limbs.
- Polydactyly: Extra fingers or toes.
- Syndactyly: Fusion of fingers or toes.
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Description
This quiz covers various chromosomal abnormalities, including numerical anomalies such as trisomies and monosomy. It provides detailed insights into specific syndromes like Klinefelter, Triple X, and Turner syndromes, exploring their causes, features, and diagnoses. Test your knowledge on these genetic conditions and their implications.
