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Chromosome Abnormality Disorders
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Chromosome Abnormality Disorders

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Questions and Answers

What is the main characteristic of a child with Patau syndrome?

  • Severe cleft lip/palate (correct)
  • Micrognathia
  • Short neck
  • Rocker-bottom feet

    • Which of the following features is NOT commonly associated with Edwards syndrome?

  • Microcephaly
  • Polydactyly (correct)
  • Prominent occiput
  • Limited hip abduction

    • In cases of translocation Down syndrome, what is essential to determine the genetic status of the parents?

  • Family history analysis
  • Karyotyping (correct)
  • Physical examination
  • Blood type testing

    • What is the median survival time for infants diagnosed with Edwards syndrome?

    <p>14.5 days</p> Signup and view all the answers

    Which statement about trisomy of chromosome 21 is true?

    <p>It is often a result of maternal age.</p> Signup and view all the answers

    Which of the following features is characteristic of Cri-du-chat Syndrome?

    <p>Cat-like cry</p> Signup and view all the answers

    What is the primary cause of Trisomy 21?

    <p>Chromosomal nondisjunction</p> Signup and view all the answers

    Which of the following statements about microdeletion syndromes is accurate?

    <p>They require molecular diagnostics for detection.</p> Signup and view all the answers

    Which of the following is a major characteristic of Turner Syndrome?

    <p>Short stature and loss of ovarian function</p> Signup and view all the answers

    What is a significant risk factor for trisomies, particularly Trisomy 21?

    <p>Increased maternal age</p> Signup and view all the answers

    Which of the following describes a presentation of Patau Syndrome caused by Trisomy 13?

    <p>Severe facial clefting</p> Signup and view all the answers

    Which syndrome is primarily recognized by a karyotype showing 5p-?

    <p>Cri-du-chat Syndrome</p> Signup and view all the answers

    For a patient with Wolf-Hirschhorn Syndrome, which clinical feature is most expected?

    <p>Microcephaly</p> Signup and view all the answers

    What is a major clinical presentation of Cri-du-chat syndrome?

    <p>Mewing cry</p> Signup and view all the answers

    Which genetic abnormality is most commonly associated with Turner Syndrome?

    <p>45,X</p> Signup and view all the answers

    Which of the following is NOT typically associated with Klinefelter Syndrome?

    <p>Webbing of the neck</p> Signup and view all the answers

    What is the expected life expectancy for individuals diagnosed with Turner Syndrome?

    <p>Normal</p> Signup and view all the answers

    What type of chromosomal abnormality does Wolf-Hirschhorn Syndrome result from?

    <p>Deletion</p> Signup and view all the answers

    What is the chromosomal composition of Klinefelter Syndrome?

    <p>47,XXY</p> Signup and view all the answers

    Which presentation is most likely seen in individuals with 45,X/46,XX mosaics compared to those with 45,X Turner Syndrome?

    <p>Normal life expectancy</p> Signup and view all the answers

    What is the likelihood of a child having translocation Down Syndrome from a parent with a Robertsonian translocation of 45 chromosomes involving chromosome 21?

    <p>100%</p> Signup and view all the answers

    What are Down Syndrome clinical presentations? TRISOMY 21 (aneuploidy)

    <ul> <li>upward slopping palpebral fissure</li> <li>short stature</li> <li>over folded helix single palmar (simian crease)</li> <li>nuchal skin in excess</li> <li>brachycephaly</li> </ul> Signup and view all the answers

    what is clinical presentation of Patau Syndrome? TRISOMY 13

    <ul> <li>cleft slip</li> <li>microcephaly</li> <li>cardiac defect</li> <li>polydactyl</li> <li>survive 7 days mean</li> </ul> Signup and view all the answers

    What is clinical presentation of Edwards Syndrome? TRISOMY 18

    <ul> <li>microcephaly</li> <li>CNS and cardiac malformations</li> <li>prominent occiput</li> <li>micrognathia</li> <li>overlapping fingers</li> <li>rocker bottom beet</li> <li>survival 14 days</li> </ul> Signup and view all the answers

    What is monosomy of sex chromosome X called? (one X and no Y or second X)

    <p>TURNER SYNDROME</p> Signup and view all the answers

    What are signs of Turner Syndrome?

    <ul> <li>classic genotype is 45X but defective second X chromosomes can also cause it</li> <li>short stature</li> <li>delayed puberty</li> <li>amenorrhea</li> <li>gonadal dysgenesis</li> <li>more common in miscarriages</li> <li>75% of live birth cases are 45X/46XX mosaic -- believed all live births are mosaic to some degree (75% MOSAIC)</li> </ul> Signup and view all the answers

    What is Trisomy of sex chromosomes where there is XX and Y (XXY)?

    <p>KLINEFELTER SYNDROME</p> Signup and view all the answers

    What is clinical presentation of Klinifelter syndrome? (XXY)

    <ul> <li>breast development (Secondary sex characteristic)</li> <li>hypogonadism</li> <li>long limbs</li> <li>tall, thin stature</li> <li>supplement testosterone</li> </ul> Signup and view all the answers

    What is SHOX GENE?

    <ul> <li>SHOX gene is on the X and Y chromosome</li> <li>it is associated with TALL stature</li> <li>all sex chromosomal TRISOMIES have 3 copies of the SHOX gene = tall stature</li> <li>Turner syndrome (sex chromosome monosomy (X)) has only ONE copy of the SHOX gene = short stature</li> </ul> Signup and view all the answers

    Difference between sex chromosome trisomy 47 XXX and 47 XYY (remember XXY is klinfelter syndrome)

    <p>The different impacts on fertility between 47,XXX and 47,XYY individuals are due to the specific roles and effects of the X and Y chromosomes in reproductive development. While an extra X chromosome in females can sometimes lead to ovarian dysfunction, an extra Y chromosome in males generally does not interfere with fertility.</p> <p>The presence of an extra X chromosome can sometimes lead to irregularities in ovarian function. The extra Y chromosome generally does not interfere with the development and function of the testes or sperm production.</p> Signup and view all the answers

    What are Barr Bodies in sex chromosome trisomy?

    <ul> <li>when you have more than 1 X chromosome it is inactivated and forms Barr Body</li> <li>most genes on the inactive X are silenced so the extra X chromosomes dont cause any major effects</li> <li>trisomies of sex chromosomes have in common relative normalcy (mental and behaviour deficit is rare)</li> </ul> Signup and view all the answers

    What does 46,XX,t(1:22)(q25:q13) indicate?

    <ul> <li>the karyotype &quot;46,XX,t(1:22)(q25:q13)&quot; describes a female with a balanced reciprocal translocation between chromosomes 1 and 22. While this typically does not affect the individual's health, it can have implications for fertility and the genetic health of future children.</li> <li>In a balanced translocation, there is no loss or gain of genetic material; the genetic material is rearranged but remains complete</li> <li>While the individual may be healthy, balanced translocations can lead to reproductive challenges. This is because during the formation of eggs or sperm, the chromosomes may not segregate properly, leading to unbalanced gametes.</li> </ul> Signup and view all the answers

    Describe what happens in Robertsonian Translocation

    Signup and view all the answers

    What does 45,XY,rob(14q21q) mean?

    <ul> <li>short arms are lost and the q arms of 14 and 21 are fused</li> <li>RT can happen at 2 different acrocentric chromosomes (like this example, 14 and 21) or it can happen at the same acrocentric chromosomes (both on 21 for example)</li> <li>RT chromosomes are 13,14,15,21.22</li> </ul> Signup and view all the answers

    What is clinical presentation of Wolf-Hirschhorn Syndrome?

    <ul> <li>broad, flat nasal bridge and high forehead</li> <li>severe mental deficiency</li> <li>karytope (4p6 critical region)</li> <li>interstitial deletions and translocations in 4p. All cases involve loss of 4p16</li> </ul> Signup and view all the answers

    What is Cri-du-chat syndrome characteristic?

    <ul> <li>cat like cry</li> <li>wide spaced eyes (hypertelorism)</li> <li>microcephaly</li> <li>mental defects</li> <li>karyotype is 5p loss. (10-20% of distal p arm is lost)</li> </ul> Signup and view all the answers

    Names of other Microdeletion syndromes (acronym and chromosomes)

    <h2>W= 7 A= 15 P= 15</h2> <p>R= 16 (microdeletions are caused by chromosomal deletions less than 5 Mbp) Wolf Hirschhorn is a microdeletion since it can only be caused by 4p16 deletion</p> Signup and view all the answers

    Study Notes

    Chromosome Abnormality Disorders

    • Trisomy 13 (Patau Syndrome): Characterized by severe cleft lip/palate, microcephaly, cardiac defects, genitourinary & renal defects and polydactyly. Most infants don't survive beyond 7 days.
    • Trisomy 18 (Edwards Syndrome): Characterized by microcephaly, CNS & cardiac malformations, prominent occiput, micrognathia, low-set ears, short neck, overlapping fingers, renal malformations, limited hip abduction, and rocker-bottom feet. Median survival is 14.5 days.
    • Trisomy 21 (Down Syndrome): Most common cause of Down Syndrome, caused by an extra copy of chromosome 21. Characterized by intellectual disability, hypotonia, specific facial features, single palmar crease, congenital heart defects, leukemia, and Alzheimer's disease.
    • Risk of Trisomy Increases with Maternal Age: The likelihood of having a child with Down Syndrome increases with the mother's age.
    • Monosomy X (Turner Syndrome): Affects females, caused by absence of one X chromosome. Most 45,X embryos are miscarried. Survivable cases often involve mosaicism, with varying presentations depending on the degree of mosaicism.
    • Turner Syndrome Presentation: Short stature, delayed puberty, amenorrhea, gonadal dysgenesis, and webbing of the neck. Life expectancy and IQ are normal.
    • Klinefelter Syndrome: Affects males, caused by an extra X chromosome (47, XXY). Characterized by tall stature, feminization of secondary sex characteristics. Life expectancy and IQ slightly below average.
    • Balanced Translocations: Individuals with balanced translocations are phenotypically normal, however they are at risk of passing an unbalanced chromosome compliment onto their offspring, increasing risk for congenital anomalies.
    • Robertsonian Translocations: 45 chromosomes in individuals with Robertsonian translocations. Balanced individuals have a high risk of having unbalanced children with congenital anomalies.
    • Down Syndrome Translocations: If a child is born with translocation Down Syndrome, it's important to karyotype the parents as there is a 1/3 chance that one parent, usually the mother, is a balanced carrier. This means they are at risk of having further children with Down Syndrome.
    • Wolf-Hirschhorn Syndrome: Caused by deletion of the p arm of chromosome 4 (4p-). Features include intellectual disability, growth retardation and the characteristic "Greek Warrior Helmet" facies.
    • Cri-du-Chat Syndrome: Caused by deletion of the p arm of chromosome 5 (5p-). Features include intellectual disability, microcephaly, and a cat-like, mewing cry.
    • Microdeletion Syndromes: Caused by chromosomal deletions less than 5 Mbp, often only detected by molecular diagnostics using DNA probes.

    Chromosome Abnormality Disorders: Summary

    • Karyotypes can be used to detect numerical chromosome abnormalities as well as large-scale autosomal deletion syndromes.
    • Trisomy 21 is the most common cause of Down Syndrome. Major presentations are intellectual disability, hypotonia, characteristic facies, single palmar crease, congenital heart defects, leukemia, and Alzheimer disease.
    • The risk of trisomies increases with advancing maternal age.
    • Trisomy 13 causes Patau Syndrome. Major presentations are severe facial clefting, cardiac, genitourinary, and renal defects. Mean survival is 7 days.
    • Trisomy 18 causes Edwards Syndrome. Major presentations are microcephaly, CNS and cardiac malformations, overlapping fingers, rocker-bottom feet. Mean survival is 14 days.
    • Monosomy for X (45, X) causes Turner Syndrome. 99% of 45, X embryos are miscarried. Most cases are 45, X/46, XX or 45, X/46, XY mosaics. Mosaics are more likely to survive to birth and may have variable presentations depending on the degree of mosaicism.
    • Major presentations of Turner Syndrome are short stature, delayed puberty, amenorrhea, gonadal dysgenesis, webbing of the neck. Life expectancy and IQ are normal.
    • Klinefelter Syndrome occurs with 47, XXY karyotypes. Major presentations are tall stature and feminization of secondary sex characteristics. Life expectancy and IQ slightly below average.
    • Individuals with balanced translocations are usually phenotypically normal but are at risk of passing an unbalanced compliment of chromosome onto their offspring and having children with congenital anomalies.
    • Carriers of Robertsonian Translocations with 45 chromosomes are balanced but have a high risk of having unbalanced children with congenital anomalies.
    • A live-born child of a 45, XX (or XY), rob(14q21q) individual has a 33% chance of having translocation Down Syndrome.
    • A live-born child of a 45, XX (or XY), rob(21q21q) individual has a 100% chance of having translocation Down Syndrome.
    • Deletion of the p arm of chromosome 4 (4p‐) causes Wolf‐Hirschhorn Syndrome. Major clinical presentations are intellectual disability and ‘Greek Warrior Helmet’ facies.
    • Deletion of the p arm of chromosome 5 (5p‐) causes Cri‐du‐Chat syndrome. Major clinical presentations are intellectual disability, microcephaly and a ‘Cat‐like’, mewing cry.

    Chromosome Abnormality Disorders: Learning Objectives

    • Use a karyotype to diagnose a disorder caused by a numerical chromosome abnormality.
    • Describe the major clinical aspects of the autosomal trisomies, aneuploidies of the sex chromosomes, and autosomal deletion syndromes (4p‐ and 5p‐).
    • Evaluate the risk to parents of having a child affected by Down Syndrome due to Trisomy 21 or Robertsonian translocations.
    • Compare the risk of miscarriage and clinical presentation of 45, X Turner Syndrome with 45, X/46, XX (or XY) mosaics.

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    Chromosome Abnormality Disorders - PDF Notes

    Description

    This quiz covers various chromosome abnormality disorders including Trisomy 13, Trisomy 18, Trisomy 21, and Turner Syndrome. Learn about their characteristics, associated risks, and how maternal age can influence the likelihood of these disorders. Test your knowledge on these critical genetic conditions.

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