Cytogenetics Overview and Prenatal Analysis

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Questions and Answers

What percentage of spontaneous abortions are associated with chromosomal abnormalities?

25%

33%

50% (correct)

66%

Which condition is characterized by eye fusion, often referred to as Cyclops?

Turner Syndrome

Klinefelter Syndrome

Edward's Syndrome

Patau's Syndrome (correct)

What is the most common type of prenatal cytogenetic analysis performed?

Chorionic Villus Biopsy

Alpha Fetoprotein Test

Umbilical Cord Blood Biopsy

Amniocentesis (correct)

What is the rate of biological elimination for Trisomy 21?

65% Signup and view all the answers

Which of the following is NOT considered a sex chromosome aneuploidy?

Trisomy 13 Signup and view all the answers

Which condition typically results in a fetal loss during the first trimester?

Trisomy 16 Signup and view all the answers

What percentage of pregnancies recognized with genetic abnormalities will end in spontaneous fetal loss?

15% Signup and view all the answers

What developmental level do babies with Edward's Syndrome typically reach if they survive?

6 months Signup and view all the answers

What is the purpose of prenatal chromosomal analysis?

To screen for possible genetic alterations Signup and view all the answers

Which type of analysis involves collecting amniotic fluid?

Amniocentesis Signup and view all the answers

Which of the following factors increases the incidence of chromosomal abnormalities?

Advanced maternal age Signup and view all the answers

What is a karyotype?

The number of chromosomes and their size distribution Signup and view all the answers

Which condition is caused by a part of the brain protruding through the occipital sutures?

Encephalocele Signup and view all the answers

What is the role of Alpha-fetoprotein (AFP) in prenatal testing?

Marker for chromosomal abnormalities Signup and view all the answers

Which procedure involves sampling tissue from the placenta?

Chorionic Villus Biopsy Signup and view all the answers

What percentage of spontaneous abortions is attributed to prenatal cytogenetic abnormalities?

50%-60% Signup and view all the answers

What is the primary purpose of venous sampling through the cervix?

To sample fetal blood for genetic analysis Signup and view all the answers

What is a common indication for conducting prenatal chromosomal analysis?

Previous child with a chromosomal abnormality Signup and view all the answers

Which of the following techniques is specifically known as cordocentesis?

Umbilical cord blood biopsy Signup and view all the answers

What chromosomal abnormality occurrence percentage applies to newborns who may require postnatal chromosomal analysis?

0.6% - 1.0% Signup and view all the answers

What type of genetic carrier status might prompt chromosomal analysis in a parent?

Carrier of unbalanced gametes Signup and view all the answers

What anomaly can indicate the need for karyotype analysis in a newborn?

Multiple congenital anomalies Signup and view all the answers

Which abnormality is associated with elevated levels of AFP in prenatal screening?

Spinal bifida Signup and view all the answers

What is a chorionic villi's role in prenatal procedures?

It allows genetic analysis via tissue sampling Signup and view all the answers

Which syndrome is characterized by having three copies of chromosome 21?

Trisomy 21 Signup and view all the answers

What is a common heart defect associated with Trisomy 21?

Ventricular septal defects Signup and view all the answers

Which condition is associated with an increased risk in individuals with Klinefelter Syndrome?

Acute Lymphoblastic Leukemia Signup and view all the answers

What is the incidence rate of Trisomy 13, or Patau Syndrome, in live births?

1:4000 to 1:15000 Signup and view all the answers

Which of the following is a feature of Turner Syndrome?

Hypogonadism Signup and view all the answers

Which chromosomal abnormality is most commonly associated with maternal age?

Trisomy 13 Signup and view all the answers

The majority of cases of Trisomy 21 result from what type of genetic event?

Meiotic nondisjunction Signup and view all the answers

Which genetic pattern describes an individual with 46 chromosomes but an additional chromosome 21?

Mosaic type Signup and view all the answers

What is a significant indication for conducting cytogenetic analysis in suspected Down Syndrome cases?

Unexplained mental retardation or developmental delay Signup and view all the answers

What does an abnormal alpha-fetoprotein (AFP) level not necessarily indicate?

Advanced maternal age Signup and view all the answers

What developmental issues are associated with Prader-Willi Syndrome due to loss of function of genes on chromosome 15?

Insatiable appetite and obesity Signup and view all the answers

What is a common characteristic of individuals with anencephaly?

Undeveloped skull with exposed brain Signup and view all the answers

Which of the following disorders is NOT indicated for cytogenetic analysis?

Childhood obesity Signup and view all the answers

During adulthood, which health issue is commonly associated with Prader-Willi Syndrome?

Diabetes mellitus type 2 Signup and view all the answers

Which chromosomal abnormality is typically assessed in cases of Turner Syndrome?

Monosomy X Signup and view all the answers

Which statement regarding alpha-fetoprotein (AFP) testing is true?

It can detect neural tube defects in a significant number of pregnancies. Signup and view all the answers

Study Notes

Cytogenetics

Cytogenetics studies chromosome structure and abnormalities.
Aneuploidy is an abnormal number of chromosomes; usually used to describe abnormal numbers of chromosomes.
Karyotype is the number of chromosomes in a normal diploid cell and their size distribution.

Prenatal Cytogenetic Analysis

Used to screen for genetic alterations during pregnancy.
Common methods: amniocentesis, chorionic villus biopsy, and umbilical cord blood biopsy.
Amniocentesis: collects amniotic fluid; chorionic villus biopsy: samples placental tissue; umbilical cord blood biopsy: involves extracting fetal blood.
Indications for prenatal testing may include advanced maternal age, multiple pregnancy losses, known family history of genetic disorders, elevated maternal serum screening results, or abnormal ultrasound findings.

Cytogenetic Abnormalities

Autosomal trisomies (extra copy of chromosomes 1-22) are a major cause of spontaneous abortions (52%).
Trisomy 18 (Edwards syndrome): Babies affected often don't survive past 6 months with a high rate of fetal loss in the first trimester.
Trisomy 13 (Patau syndrome): Characterized by striking eye fusion, which is often a critical feature.
Trisomy 21 (Down syndrome): Common chromosomal disorder; major cause of mental retardation; incidence of ~1 in 700 live births.
Sex chromosome aneuploidies: Include 47,XXX females, 47,XXY males, 47,XXX, Klinefelter syndrome, and Turner syndrome.
Klinefelter syndrome (47,XXY): Males with this condition typically have lower than normal levels of testosterone, with possible symptoms such as underdeveloped testes, gynecomastia, and infertility
Turner syndrome (45,X): Females with this condition have only one X chromosome; they usually have short stature, developmental delays, and/or heart defects; may have a higher risk of medical conditions throughout their lifetime.
Microdeletion syndromes: Include Angelman syndrome and Prader-Willi syndrome.

Prenatal Testing

Alpha-fetoprotein (AFP) levels can detect neural tube defects.

Chromosomal Analysis - Postnatal

May be indicated for patients with phenotypic abnormalities or diagnosed genetic disorders, or cases of infertility, or multiple spontaneous abortions.

Childhood and Adult Cytogenetics

Various tests assess for a broad range of possible issues in patients.

Trisomy 13/Patau Syndrome

Incidence of ~1 in 4,000-15,000 live births.
Caused by meiotic nondisjunction; associated with maternal age.
Key characteristics include microcephaly, mental retardation, microphthalmia, cleft lip/palate, polydactyly, cardiac defects, and renal defects.

Trisomy 18/Edwards Syndrome

Incidence of ~1 in 8,000 live births.
Due to meiotic nondisjunction, with an association with maternal age.
Individuals have low birth weight, mental retardation, micrognathia, prominent occiput, malformed ears, heart defects, and renal malformations, which often lead to death within the first year.

Trisomy 21/Down Syndrome

A prevalent chromosomal disorder.
Caused by meiotic nondisjunction; associated with maternal age.
Major characteristics include growth retardation, broad face, upward-slanting eyes, short nose, short stature, many "loops" on the fingertips, a small and arched palate, a broad hand, prominent palmar crease, intellectual disabilities with an associated IQ range from 20-60, delayed puberty/early menopause, and potential for congenital heart disease or intestinal blockages.

Sex Chromosome Aneuploidies

Conditions like Klinefelter syndrome (47,XXY), Turner syndrome (45,X), and XYY syndrome affect both males and females.
These conditions typically include various phenotypic features and complications, notably concerning reproductive and developmental outcomes.

Microdeletion Syndromes

Prader-Willi syndrome and Angelman syndrome are disorders connected to deletions within chromosome 15.
Prader-Willi syndrome is characterized typically by hypotonia, decreased ability to regulate appetite (a major driver of obesity), intellectual disabilities, short stature, other issues.
Angelman syndrome features include severe intellectual disability, seizures, jerky movements (ataxia), unusual laughter, and other characteristics.

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Description

This quiz covers the fundamentals of cytogenetics, including chromosome structure, aneuploidy, and karyotype analysis. It also explores prenatal cytogenetic methods like amniocentesis and chorionic villus biopsy, along with the implications of cytogenetic abnormalities. Test your understanding of these critical concepts in genetics.