CHROMOSOMAL ABERRATIONS Flashcards
Breakage of a chromosome that leads to a variety of rearrangements affecting the genes of that chromosome
Even if all chromosomes are present in normal numbers, abnormalities in the chromosome structure may cause disorder
Chromosomal Aberrations
Or Alterations of Chromosomal Structure
Occurs when a fragment of a chromosome is lost
Deletion
Large deletions tend to have the most serious effects
Deletion that occurs towards the end of a chromosome
ABC O DEFG → BC O DEFG
Terminal Deletion
Deletion that occurs from the interior of chromosomes
ABC O DEFG → A O DEFG
Interstitial Deletion
or Intercalary Deletion
Small deletion up to 5MB, a doze of genes
MB: Million base pairs
Microdeletion
Occurs when a fragment from one chromosome joins a homologous chromosome
Duplication
Duplicated segment is present in another genome
ABC O DEFG → LMN O PQREFG
Interchromosomal Duplication
ABC O DEFG → LMN O PQREFG
Duplicated segment is present in the same chromosome
Intrachromosomal Duplication
3 Subtypes for Tandem Repeat
Tandem Repeats under Intrachrosomal Duplication
Gene order of duplicated segment is that of the original segment
Immediately after original segment
ABC O DEFG → ABC O DEFGEFG
Direct Tandem
Intrachromosomal Duplication
Tandem Repeats under Intrachrosomal Duplication
Gene order of the duplicated segment is reversed
ABC O DEFG → ABC O DEFGGFE
Reverse Tandem
Intrachromosomal Duplication
Tandem Repeats under Intrachrosomal Duplication
Duplicated segment is removed from the original segment
ABC O DEFG → ABC O DEFG ?? [TBF]
Displaced Tandem
Intrachromosomal Duplication
Occurs when a fragment breaks off reattaches within the same chromosome in an altered orientation
All the genes are still present in their normal number, but switching is present. Not as bad as getting syndromes from the other types
Inversion
Inversion that does not include the centromere
Either the p or q arm is inverted
Paracentric Inversion
ABC O DEFG → ABC O DEFG ?? [TBF]
Inversion that includes the centromere
Both the p or q arm is inverted
Pericentric Inversion
ABC O DEFG → ABC O DEFG ?? [TBF]
Occurs when a chromosomal fragment attaches to a non-homologous chromosome
Translocation
Like inversions, translocations may or may not be harmful
Chromosomal changes present in sperm or egg
Chromosomal Translocation
Translocation where two non-homologous chromosomes exchange segments
Reciprocal Translocation
Translocation caused by two particular chromosomes joining together
Only occurs with chromosomes: 13, 14, 15, 21, 22
Occurs when the long arms of two acrocentric chromosomes fuse at the centromere and the two short arms are lost
Robertsonian Translocation
A usual type of chromosome rearrangement
Identify the Type of Aberration
Wolf-Hirschhorn Syndrome
also known as Pitt Syndrome
Caused by a ____ of a distal short arm of chromosome 4
Deletion
Identify the Type of Aberration
Jacobsen Syndrome
also known as 11q terminal ____
Deletion
Identify the Type of Aberration
Cat-eye Syndrome
Most often caused by a chromosome abnormality called an inverted ____ 22 ( ____ of the chromosome 22)
Duplication
Identify the Type of Aberration
Edward’s Syndrome
Trisomy 18: Occurs when a baby is born with three copies of chromosome 18 instead of two
Duplication
Identify the Type of Aberration
Patau Syndrome
Trisomy 13: Occurs when a baby is born an additional copy of all or part of chromosome 13
Duplication
Identify the Type of Aberration
Hemophilia A
F8 gene (X chromosome) ____
Inversion
Identify the Type of Aberration
____ Down Syndrome
Occurs as a ____ between chromosome 14 and 21
Translocation
Down Syndrome
Trisomy 21: Occurs when a baby is born with three copies of chromosome 21
Duplication
Types of Chromosomal Aberrations (4)
- Deletion
- Duplication
- Inversion
- Translocation
