Chapter 8
Chromosomal aberrations: substancial changes in chromosome structure or number
Cytogenetics: Examination of chromosomes
P = short side (petit)
q = tall side (beneden)
P-3.4
Metacentric: in the middle
Submetacentric: q is a little longer
Acrocentric: p is short
Telocentric: p non existent
Deletion: loss of a segment
-Terminal deletion: single break (ends)
-Interstitial deletion: 2 breaks and reattachment (middle)
Duplication: repetition of a segment (less harmful)
Inversion: change in direction in a segment
-Pericentric inversion: centromere is between inverted region
-Paracentric inversion: centromere outside inverted region
Translocation: segment of one chromosome on another chromosome
-Simple translocation: One-way transfer
-Reciprocal translocation: Two-way exchange
Homologous gene: 2 genes from a common ancestor
Paralogs gene: homologous genes within a single species
Copy number variation: multiple of lacking of a gene depending on the individual
Balanced translocation: no phenotypic abnormalities
Unbalanced translocation: phenotypic abnormalities in children with parents with balanced
translocation
Inversion/translocation:
Break point effect: breaking in a vital gene
Position effect: reposition changed expression CANCER QUESTION
- Moved next to regulatory sequence: activate other gene
- Moved in heterochromatic region (gene that normally is inactive becomes
constitutively active)
Heterochromatin: compact region, generally inactive
Centromere and telomere are very compact (heterochromatin)
Constitutive heterochromatin: permanently inactive
Facultative heterochromatin: regions with euchromatin and heterochromatin (X
chromosome)
Chromosomal aberrations: substancial changes in chromosome structure or number
Cytogenetics: Examination of chromosomes
P = short side (petit)
q = tall side (beneden)
P-3.4
Metacentric: in the middle
Submetacentric: q is a little longer
Acrocentric: p is short
Telocentric: p non existent
Deletion: loss of a segment
-Terminal deletion: single break (ends)
-Interstitial deletion: 2 breaks and reattachment (middle)
Duplication: repetition of a segment (less harmful)
Inversion: change in direction in a segment
-Pericentric inversion: centromere is between inverted region
-Paracentric inversion: centromere outside inverted region
Translocation: segment of one chromosome on another chromosome
-Simple translocation: One-way transfer
-Reciprocal translocation: Two-way exchange
Homologous gene: 2 genes from a common ancestor
Paralogs gene: homologous genes within a single species
Copy number variation: multiple of lacking of a gene depending on the individual
Balanced translocation: no phenotypic abnormalities
Unbalanced translocation: phenotypic abnormalities in children with parents with balanced
translocation
Inversion/translocation:
Break point effect: breaking in a vital gene
Position effect: reposition changed expression CANCER QUESTION
- Moved next to regulatory sequence: activate other gene
- Moved in heterochromatic region (gene that normally is inactive becomes
constitutively active)
Heterochromatin: compact region, generally inactive
Centromere and telomere are very compact (heterochromatin)
Constitutive heterochromatin: permanently inactive
Facultative heterochromatin: regions with euchromatin and heterochromatin (X
chromosome)
