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Questions and Answers
What is the primary consequence of unbalanced chromosomal aberrations?
What type of structural aberration involves the loss of a chromosomal segment resulting in a looped structure?
Which type of chromosomal aberration results in two copies of the same gene on a chromosome?
Which of the following describes a Robertsonian translocation?
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What defines a pericentric inversion in structural aberrations?
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In isochromosomes, what is the characteristic feature of the chromatids?
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What is a common result of structural chromosomal aberrations like Cri du chat syndrome?
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In reciprocal translocation, what is a key feature?
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What is the potential risk for a child when a parent carries a translocation involving chromosome 21?
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Study Notes
Chromosomal Aberrations
- Definition: Deviation from normal number or structure of chromosomes
- Common causes: Congenital disorders and developmental problems
- Structural aberrations are mutations
- Balanced aberration: chromosome has normal genetic material
- Unbalanced aberration: chromosome has missing genetic material
Structural Aberrations Types
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1- Break:
- Result of a break in a chromosome, followed by reunion.
- Reunion occurs via sticky ends
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2- Deletion: Loss of fragmented part of a chromosome
- Terminal: Loss of a portion at the end of a chromosome
- Interstitial: Loss of a segment of a chromosome in between two other points
- Examples: Wolf-Hirschhorn syndrome (deletion of short arm of chromosome 4), Cri-du-chat syndrome (deletion of short arm of chromosome 5)
- Ring chromosome: loss + reunion in a ring
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3- Duplication:
- Addition of extra piece of homologous chromosome
- Result of unequal crossing over
- Two copies of the same gene on a chromosome
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4- Inversion:
- Two breaks in a chromosome, followed by reunion in inverted form
- Pericentric: Break on both sides of the centromere
- Paracentric: Break on one side of the centromere
- Two breaks in a chromosome, followed by reunion in inverted form
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5- Translocation:
- Transfer of chromosome segment to a non-homologous chromosome
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Robertsonian translocation (centric fusion): Involves acrocentric chromosomes; fusion of long arms of two acrocentric chromosomes; loss of both short arms (e.g., chromosome 14 and 21, in Down syndrome cases)
- Risk of having a child with Down syndrome, if a parent is a carrier, can be up to 100%
- Reciprocal translocation: Exchange of segments between non-homologous chromosomes; balanced (no genes lost or added) example (chromosome 22 and 9).
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Robertsonian translocation (centric fusion): Involves acrocentric chromosomes; fusion of long arms of two acrocentric chromosomes; loss of both short arms (e.g., chromosome 14 and 21, in Down syndrome cases)
- Transfer of chromosome segment to a non-homologous chromosome
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6- Isochromosomes: Result from a division of a chromosome during anaphase of mitosis.
- Two non-similar chromatids are created
- Two non-similar chromosomes form
- One chromosome will have two long arms and one will have two short arms (e.g., in some cases of submetacentric chromosomes)
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Description
Test your knowledge on chromosomal aberrations and their types. This quiz covers definitions, causes, and specific structural aberrations such as deletions and duplications. Ideal for students studying genetics or molecular biology.
