Chromosomal Abnormalities Flashcards
What is polyploidy?
Abnormal number of chromosomes - A multiple of the haploid chromosome number but greater than the diploid number.
How can chromatin be made inactive?
DNA methylation
Histone deacetylation
What is aneuploidy?
Abnormal number of chromosomes which is not a multiple of the haploid number
What is monosomy?
Loss of one homologous chromosome
What is trisomy?
Gain of one homologous chromosome
What is euchromatin?
Lightly packed chromatin often under active transcription
What is heterochromatin?
Tightly packed chromatin
What is a balanced structural abnormality?
When there is a physical change to one or more of the chromosomes but no missing or extra genetic information
What is a chromosome inversion?
Genetic material is rearranged within one chromosome
What is a ring chromosome?
Loss of telomeres or ends of both arms to form a ring
What is an isochromosome?
Creation of two non-identical chromosomes - one a combination of two short arms, one with two long arms
What is reciprocal translation?
Exchange of genetic material between two non-homologous chromosomes
What is a Robertsonian translocation?
Rearrangement between two chromosomes
-q arms of two acrocentric chromosomes combine to form one ‘super-chromosome’ with the loss of both p arms because they are so small
How are chromosomes numbered?
According to their size and position of centromere
How is chromosome nomenclature done?
State number of chromosomes
State sex chromosomes observed eg 46, XX
A +/- then a number indicates extra/missing chromosomes
A chromosome number then p/q indicates a missing/extra arm
