5-Chromosomal_Abnormalities_Flashcards
How many chromosomes do humans typically have?
46 chromosomes (23 pairs).
What are the two types of chromosomes in humans?
Autosomes (22 pairs) and sex chromosomes (1 pair: XX or XY).
What are chromosomal abnormalities?
Errors in the number or structure of chromosomes leading to health problems.
What are some effects of chromosomal abnormalities?
Miscarriages, stillbirths, malformations, intellectual disabilities, and identifiable syndromes.
What are the two main categories of chromosomal abnormalities?
Numerical and structural disorders.
What is aneuploidy?
A deviation from the normal diploid number of chromosomes.
Give an example of aneuploidy.
Trisomy (2n+1) or monosomy (2n-1).
What is polyploidy?
A change involving multiples of the haploid set of chromosomes (e.g., triploidy, tetraploidy).
What is a deletion?
Loss of a chromosome segment.
What is a translocation?
Exchange of segments between chromosomes.
What is an inversion?
Reversal of a chromosome segment.
What is a ring chromosome?
A chromosome forms a circular structure due to end fusion.
What are the two types of cell division where errors can occur?
Mitosis and meiosis.
What is nondisjunction?
Failure of chromosomes to separate properly during cell division.
What is mosaicism?
Presence of two or more cell populations with different genotypes from one zygote.
What causes Down syndrome (Trisomy 21)?
An extra copy of chromosome 21.
What are some characteristics of Down syndrome?
Intellectual disability, distinct facial features, and heart defects.
What causes Patau syndrome (Trisomy 13)?
An extra copy of chromosome 13.
What is the prognosis for Patau syndrome?
Most affected individuals die within the first year of life.
What causes Edwards syndrome (Trisomy 18)?
An extra copy of chromosome 18.
What is the prognosis for Edwards syndrome?
Most affected individuals die within the first year of life.
What causes Turner syndrome (XO)?
Missing one X chromosome in females (45, XO).
What are some features of Turner syndrome?
Short stature, webbed neck, and infertility.
What causes Klinefelter syndrome (XXY)?
An extra X chromosome in males (47, XXY).
What are characteristics of Klinefelter syndrome?
Infertility, reduced body hair, and learning difficulties.
What is Triple X syndrome (XXX)?
Females with an extra X chromosome (47, XXX).
What is Double Y syndrome (XYY)?
Males with an extra Y chromosome (47, XYY).
What is Cri-du-chat syndrome?
Deletion on the short arm of chromosome 5.
What causes DiGeorge syndrome?
Microdeletion on chromosome 22q11.2.
What is Angelman syndrome?
Deletion on chromosome 15 inherited from the mother.
What is Prader-Willi syndrome?
Deletion on chromosome 15 inherited from the father.
What is a Robertsonian translocation?
Fusion of long arms of two acrocentric chromosomes.
What is cytogenetics?
Study of chromosomes, their structure, and inheritance.
What is karyotyping?
Visual representation of chromosomes arranged in pairs.
What does G-banding in karyotyping do?
Produces characteristic banding patterns for chromosome identification.
What is FISH (Fluorescence In Situ Hybridization)?
A technique to detect specific DNA sequences using fluorescent probes.
What is spectral karyotyping (SKY)?
Assigns a different color to each chromosome for visualization.
What is array-CGH?
High-resolution technique to detect DNA gains or losses.
How is a normal female karyotype written?
46, XX.
How is Down syndrome written in karyotype notation?
47, XY, +21.
What does ‘del’ indicate in karyotype nomenclature?
Deletion.
What does ‘t’ indicate in karyotype nomenclature?
Translocation.
What disorders can cytogenetic testing diagnose?
Down syndrome, Turner syndrome, and Cri-du-chat syndrome.
What is the role of cytogenetics in genetic counseling?
Provides families with information on chromosomal abnormality risks.
How is prenatal screening performed?
Through amniocentesis or chorionic villus sampling.
What are euchromatin and heterochromatin?
Euchromatin is transcriptionally active; heterochromatin is condensed and inactive.
What are Barr bodies?
Inactivated X chromosomes in females.
What does XCI stand for?
X-chromosome inactivation.
What is the typical size of the human genome?
3.2 billion base pairs.
What is the ISCN?
International System for Human Cytogenetic Nomenclature.
