Chromosomal Aberrations Overview
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Questions and Answers

What is one of the main classifications of chromosomal aberrations?

  • Functional aberrations
  • Physiological aberrations
  • Behavioral aberrations
  • Structural aberrations (correct)

Which condition is an example of aneuploidy?

  • Translocation
  • Tetraploidy
  • Down syndrome (correct)
  • Triploidy

Which maternal factor is associated with an increased risk of chromosomal aberrations?

  • Low vitamin D levels
  • High blood pressure
  • Advanced maternal age (correct)
  • Maternal smoking

What type of structural aberration involves losing a segment of a chromosome?

<p>Deletion (C)</p> Signup and view all the answers

Which infection is known to cause fragmentation of chromosomes?

<p>German measles (B)</p> Signup and view all the answers

Which of the following best describes polyploidy?

<p>Three or more complete sets of chromosomes (A)</p> Signup and view all the answers

What is a common chemical agent that increases the risk of chromosomal aberrations?

<p>Formaldehyde (A)</p> Signup and view all the answers

What is not considered a type of structural chromosomal abnormality?

<p>Trisomy (C)</p> Signup and view all the answers

What is Turner syndrome characterized by at the chromosomal level?

<p>45 chromosomes with a missing X chromosome (C)</p> Signup and view all the answers

Which of the following does NOT occur in polyploidy?

<p>Monosomy (C)</p> Signup and view all the answers

What is the karyotype for Klinefelter syndrome?

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

Which factor can lead to non-disjunction and subsequent chromosomal abnormalities?

<p>Drugs affecting microtubule systems (D)</p> Signup and view all the answers

What is the chromosome composition in individuals with super female syndrome?

<p>47, XXX (A)</p> Signup and view all the answers

In the context of chromosomal abnormalities, what does di-spermy refer to?

<p>Fertilization of an egg by two sperm (D)</p> Signup and view all the answers

Which condition is characterized by cells having three sets of chromosomes?

<p>Triploidy (A)</p> Signup and view all the answers

What is a common feature seen in individuals with Turner syndrome?

<p>Limb edema (D)</p> Signup and view all the answers

What is the result of non-disjunction during meiosis I?

<p>2 normal and 2 abnormal daughter cells (C)</p> Signup and view all the answers

Which syndrome is caused by a trisomy of chromosome 21?

<p>Down syndrome (C)</p> Signup and view all the answers

Which of the following is a characteristic associated with Klinefelter syndrome?

<p>Presence of Barr body (A)</p> Signup and view all the answers

What cellular event leads to the condition of mosaicism?

<p>Non-disjunction during early mitotic divisions (B)</p> Signup and view all the answers

What is the chromosomal make-up of a male with Klinefelter syndrome?

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

What is a potential outcome of anaphase lag during cell division?

<p>Micronucleus formation (C)</p> Signup and view all the answers

What condition is associated with the presence of two Barr bodies?

<p>Multiple X syndrome (B)</p> Signup and view all the answers

What is a feature of Down syndrome's chromosomal makeup?

<p>47 chromosomes total (C)</p> Signup and view all the answers

What is the main characteristic of reciprocal translocation?

<p>It requires breakage and exchange between non-homologous chromosomes. (B)</p> Signup and view all the answers

Which type of translocation is characterized by the loss of short arms from two chromosomes?

<p>Robertsonian translocation (C)</p> Signup and view all the answers

How many chromosomes does a person typically have after a Robertsonian translocation?

<p>45 chromosomes (D)</p> Signup and view all the answers

Which of the following is an example of a disease associated with reciprocal translocation?

<p>Chronic myeloid leukemia (B)</p> Signup and view all the answers

What is meant by para-centric inversion?

<p>It involves two breaks in one arm without involving the centromere. (D)</p> Signup and view all the answers

In the process of insertion, which scenario applies?

<p>A segment of one chromosome is translocated and inserted into a different region of the same chromosome. (C)</p> Signup and view all the answers

What is the primary consequence of inversion on genetic material?

<p>It reverses the position of the segment within the same chromosome. (A)</p> Signup and view all the answers

Which chromosomes are most frequently associated with Robertsonian translocation?

<p>Chromosomes 14 and 21 (C)</p> Signup and view all the answers

What characterizes an iso-chromosome?

<p>It has mirror image arms. (B)</p> Signup and view all the answers

What is the primary feature of a duplication in a chromosome?

<p>It involves the presence of two copies of a segment. (B)</p> Signup and view all the answers

What is a defining characteristic of a dicentric chromosome?

<p>It contains two centromeres. (C)</p> Signup and view all the answers

What causes the fragile X chromosome to be identified?

<p>An unusual narrow site seen under a microscope. (C)</p> Signup and view all the answers

Which prenatal screening method involves extracting amniotic fluid?

<p>Amniocentesis. (D)</p> Signup and view all the answers

What happens to a dicentric chromosome during mitosis?

<p>It is torn apart and its parts are divided. (C)</p> Signup and view all the answers

Which chromosomal abnormality is known to feature both deletion and duplication?

<p>Iso-chromosome. (B)</p> Signup and view all the answers

Which of the following best describes the instability of a dicentric chromosome?

<p>It is unstable and torn apart during mitosis. (B)</p> Signup and view all the answers

What type of diagnostic test involves a small sample of blood taken from the umbilical cord?

<p>Cordocentesis (D)</p> Signup and view all the answers

Which chromosomal alteration involves a segment being reversed end to end?

<p>Inversion (D)</p> Signup and view all the answers

Cri-du-chat syndrome is associated with which type of chromosomal alteration?

<p>Deletion (A)</p> Signup and view all the answers

Which of the following syndromes is a structural chromosomal anomaly?

<p>Wolf-Hirschhorn syndrome (D)</p> Signup and view all the answers

Para-centric inversion involves which of the following?

<p>Two breaks occurring in the same chromosome arm (B)</p> Signup and view all the answers

Which method analyzes the chromosomes for structural changes?

<p>FISH technique (D)</p> Signup and view all the answers

What is the primary purpose of chorionic villus sampling?

<p>To obtain fetal DNA for genetic testing (C)</p> Signup and view all the answers

Which of the following best describes translocation?

<p>The movement of a segment to another chromosome (C)</p> Signup and view all the answers

Flashcards

Chromosomal Aberrations

Disorders involving changes in the number or structure of chromosomes, affecting autosomes, sex chromosomes, or both.

Numerical Aberrations

Changes in the number of chromosomes.

Structural Aberrations

Changes in the structure of chromosomes, meaning the chromosomes are broken or rearranged.

Aneuploidy

An abnormal number of chromosomes (extra or missing).

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Trisomy

A type of aneuploidy with a extra copy of a chromosome.

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Down Syndrome

A genetic disorder caused by trisomy 21 (an extra copy of chromosome 21).

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Klinefelter syndrome

A genetic disorder in males caused by an extra X chromosome (47, XXY).

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Causes of Chromosomal Aberrations

Environmental factors (radiation, chemicals), maternal age, family history, and medical conditions (autoimmune diseases, infections) can increase the risk of chromosomal abnormalities.

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Nondisjunction in Meiosis I

Failure of homologous chromosomes to separate during meiosis I, resulting in gametes with an extra or missing chromosome.

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Nondisjunction in Meiosis II

Failure of sister chromatids to separate during meiosis II, resulting in gametes with an extra or missing chromosome.

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Multiple X Syndrome

A genetic condition in females, characterized by an extra X chromosome (XXX).

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Anaphase Lag

The failure of a chromosome to properly migrate to a pole during anaphase, potentially leading to the loss of a chromosome.

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Mosaicism

A genetic condition where different cells in an individual have different chromosome numbers.

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Trisomy of sex chromosomes

A genetic condition where a person has three copies of one of the sex chromosomes (X or Y) instead of the usual two.

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Super female (47, XXX)

A female with an extra X chromosome, typically experiencing no significant physical abnormalities or symptoms.

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Turner syndrome

A genetic condition in females where one of the X chromosomes is missing or partially missing (45, XO).

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Monosomy

The condition of having only one copy of a particular chromosome, instead of the usual two.

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Polyploidy

A genetic condition where cells have three or more complete sets of chromosomes.

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Triploidy

A type of polyploidy in which cells have three sets of chromosomes.

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Non-disjunction

The failure of chromosomes to separate properly during cell division (meiosis or mitosis).

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Ring chromosome

A chromosome shaped like a ring due to a deletion at both ends and fusion of the broken ends. The affected chromosome lacks telomeres.

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Reciprocal translocation

A structural abnormality where two non-homologous chromosomes exchange genetic material. Both chromosomes break at the same time.

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Philadelphia chromosome

A specific type of reciprocal translocation involving chromosomes 9 and 22. It's associated with chronic myeloid leukemia.

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Robertsonian translocation

A specific type of translocation involving acrocentric chromosomes, characterized by the fusion of long arms and loss of short arms.

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Inversion

A structural abnormality where a segment of a chromosome is inverted.

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Para-centric inversion

A type of inversion where the inverted segment does not include the centromere. Both breaks occur on the same arm.

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Inter-chromosome insertion

A type of insertion where a segment of one chromosome is inserted into another non-homologous chromosome.

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Intra-chromosomal insertion

A type of insertion where a segment of a chromosome is inserted into a different region of the same chromosome.

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Insertional Translocation

A type of chromosomal translocation where a segment of one chromosome breaks off and inserts itself into a different chromosome.

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Isochromosome

An abnormal chromosome formed when a chromosome divides transversely instead of longitudinally, resulting in two identical arms.

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Duplication

The presence of two copies of a segment of a chromosome, leading to a double dose of genes.

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Dicentric Chromosome

A chromosome with two centromeres, formed when two non-homologous chromosomes break and fuse.

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Fragile Site

A narrow, susceptible region on a chromosome, often associated with chromosome breakage.

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Fragile X Syndrome

A genetic disorder caused by a fragile site on the X chromosome, often leading to mental retardation.

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Amniocentesis

A prenatal screening test where amniotic fluid is sampled to diagnose chromosomal abnormalities.

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Chorionic Villus Sampling

A prenatal screening test where a sample of chorionic villi is taken to diagnose chromosomal abnormalities.

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Karyotype Test

A test that analyzes the number and structure of chromosomes in a sample of cells.

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FISH technique

A technique that uses fluorescent probes to detect specific DNA sequences on chromosomes.

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Chromosomal anomaly

Any change in the number or structure of chromosomes.

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Cri-du-chat syndrome

A rare genetic disorder caused by a deletion on chromosome 5.

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Inversion (chromosomal)

A structural chromosomal anomaly where a segment of a chromosome is flipped.

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Translocation (chromosomal)

A structural chromosomal anomaly where a piece of one chromosome breaks off and attaches to another.

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Study Notes

Chromosomal Aberrations (Abnormalities)

  • Definition: Disorder involving morphological or numerical alteration in single or multiple chromosomes. This affects autosomes, sex chromosomes, or both.
  • Numerical aberrations: Abnormality in the number of chromosomes.
  • Structural aberrations: Abnormality in the structure of chromosomes.

Causes Increasing the Risk of Chromosomal Aberrations

  • Environment:
    • Exposure to radiation (X-rays).
    • Chemical agents (formaldehyde, pesticides, food preservatives, tobacco).
    • Cytotoxic drugs (cholchicine, tetracyclines).
    • Maternal age (older pregnancy increases risk of non-disjunction).
    • Presence of chromosomal imbalance in family members (family tendency).
  • Medical conditions:
    • Autoimmune diseases.
    • Hypothyroidism.
    • Infections (e.g., German measles, causing fragmentation).

Numerical Aberrations

  • A- Aneuploidy: An abnormal number of chromosomes (not a multiple of the haploid number).

    • 1- Trisomy (2n+1): Presence of three copies of a particular chromosome instead of two.
      • Most autosomal trisomies are lethal (e.g., Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13) are significant chromosomal disorders characterized by developmental challenges and distinct physical features.).
      • Some sex chromosome trisomies, such as Klinefelter syndrome (47, XXY), and conditions like triple X syndrome (super female) and XYY syndrome (super male), often result in individuals who can lead relatively normal lives despite certain health risks..
    • II- Monosomy (2n-1): Loss of a single chromosome.
      • Most autosomal monosomies are incompatible with life.
      • Sex chromosome monosomies can sometimes be viable (e.g., Turner syndrome)

  • B- Polyploidy: Presence of three or more sets of chromosomes.

    • Triploidy (3n).
    • Tetraploidy (4n).
    • Pentaploidy (5n).
    • Polyploidy in general.

Causes of Aneuploidy

  • Nondisjunction: Failure of homologous chromosomes or sister chromatids to separate properly during cell division (meiosis or mitosis).
    • Primary nondisjunction: Failure in the first meiotic division.
    • Secondary nondisjunction: Failure in the second meiotic division or during mitosis.
    • Mosaicisms: Non-disjunction during mitosis, after multiple normal mitotic divisions.
  • Failure of chromosome duplication (during S phase).
  • Anaphase lag (failure of chromosome to move to a pole during anaphase).

Structural Aberrations

  • Deletion (del): Loss of a portion of a chromosome.
    • Terminal deletion: Loss of the end of a chromosome segment.
    • Interstitial deletion: Loss of an interior segment of a chromosome.
  • Ring chromosome: Two breaks at the ends of a chromosome, with the lost ends joining to form a ring.
  • Inversion: Reversal of a segment of a chromosome.
    • Paracentric: Inversion does not include the centromere.
    • Pericentric: Inversion includes the centromere.
  • Translocation: Transfer of a chromosome segment to a different non-homologous chromosome.
    • Reciprocal translocation: Exchange of segments between two non-homologous chromosomes. (e.g., Philadelphia chromosome).
    • Robertsonian translocation: Fusion of two acrocentric chromosomes at their centromeres, resulting in a single large chromosome and one small chromosome (lost).
  • Insertion: Movement of a part of one chromosome to another (inter- or intra-chromosomal).
  • Isochromosome: Chromosome with mirror image arms (duplication of one arm and deletion of the other).

Chromosomal Aberration Diagnosis

  • Prenatal screening: Blood tests, ultrasound (e.g., Down syndrome signs).
  • Prenatal tests during pregnancy: Amniocentesis, chorionic villus sampling, percutaneous umbilical blood sampling (cordocentesis).
  • Postnatal diagnosis: Physical examination, karyotyping (analysis of chromosomes), FISH (fluorescence in situ hybridization), banding techniques.

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Chromosomal Abnormalities Tutorial Session 2024/2025 (PDF)

Description

This quiz covers the definitions and types of chromosomal aberrations, including both numerical and structural abnormalities. It will also explore various environmental and medical causes that increase the risk of these anomalies. Test your understanding of the factors contributing to chromosomal disorders.

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