Abnormalities of Chromosome Structure Flashcards
Which chromosomes are acrocentric?
13, 14, 15, 21, 22
What is located in the P arm of acrocentric chromosomes?
rRNA genes
T/F One centromere and one telomere are required for chromosome stability
False, one centromere and two telomeres are required for stability
There are two types of structural abnormalities, balanced and unbalanced. Which one is associated with a normal phonotype and reproductive risk?
Balanced abnormalities
Which structural abnormality (balanced or unbalanced) leads to loss or gain of genetic material?
Unbalanced: also has a high likelihood of abnormal phenotype
A structural abnormality resulting in 3 copies of a particular chromosome segment
Partial trisomy
A structural abnormality resulting in only one copy of a chromosome segment
Partial monosomy
Structural abnormalities that are present in offspring but not in either parent are known as?
De novo
Structural abnormalities that run through families in pedigree form?
Familial
Present in all cells of body?
Constitutional
Abnormality arising in somatic cell of single tissue; typically applied to cancer lineages
Acquired
What are the phenotypic consequences of unbalanced karyotypes?
- Developmental delay (intellectual disability)
- Growth delay
- Facial dysmorphology and physical malformations
- Congenital organ malformations (like heart defects)
Long arm fusion of any two acrocentric chromosomes
Robertsonian translocation
What is the chromosome number after a Robertsonian translocation?
45, because two chromosomes have fused to one. You have loss of the short arms, but that’s ok for acrocentric chromosomes
Deletion would result in?
Partial monosomy
Abnormal chromosome consisting of two copies of one arm and no copy of the other arm
Isochromosome
Result of isochromosome?
Partial monosomy and partial trisomy
Clinically important examples of isochromosomes?
Turner syndrome, Down syndrome
Duplication of a segment of chromosome leads to?
Partial trisomy
Inversion of segment of chromosome leads to?
Normal phenotype (cuz all genes are still there) but reproductive risk (cuz of crossing over in meiosis I)
