Abnormalities in Chromosom Structure ( Self and Lecture ) Flashcards
What is the leading cause of intellectual disability and pregnancy loss?
Abnormal structure of chromosomes.
What does a metacentric chromosome look like ?
Two long arms and two short arms combined at the centromere.
What does a sub-metacentric chromosome look like?
Two very short arms, and two short arms combined at the centromere.
What does an acrocentric chromosome look like?
Two short arms combined at the centromere with two bairly discernable arms sticking off of the centromere.
If you wanted to diagnose deletions what resolution would you want the chromosome at?
Very condensed forms make it easy to discern chromosomal deletions.
What is the relation to chromosomal condensation to band resolution?
More condensed means there will be a lower band resolution.
What two things are required for chromosome stability?
One Centromere and two terminal telomeres.
What do you call a rearrangement where the net amount of genomic material stays the same?
A balanced rearrangement
What is an imbalanced rearrangement?
When the net genetic material does not stay the same
What is a partial trisomy?
Rearrangement that results in 3 copies of a chromosome segment.
What is a partial monosomy?
Rearrangement that results in one copy of a chromosome segment.
What does De Novo mean?
A structural abnormality that is new
What is a familial abnormality?
One that passes through a familial pedigree
What is a constitutional abnormality?
Menas it is present in all cells in the body
What is an acquired abnormality?
Arises in somabit cells of a single tissue. Usually applied to cancer lineages.
What will an autosomal imbalance cause?
Developmental delay, Growth Delay, Facial Dysmorphology and physical malformations.
What results in a worse phenotype, alterations in autosomes or sex chromosomes.
Autosomal inbalance results in a more severe phenotypic change. This is due to the fact that the body can survive with only one X and the second X is usually down regulated.
What is a reciprocal translocation?
Break and Exchange of gene segments between two non homologous chromosomes
Which is the long arm of a chromosome, P portion or Q portion ?
P portion. “P is for Petite”
What is the most likely segregation pattern for a reciprocal translocation?
Alternate, meaning the gamete recieves the two normal or two abnormal chromosomes.
What is the risk associated pattern of reciprocal translocation?
Adjacent segregation, where the gamete receives one normal and one abnormal chromosome.
Why does adjacent translocation carry a high risk ?
The gamete will have an unbalanced karyotype which will result in a partial monosomy and partial trisomy
What type of chromosomes will undergo robertsonian translocation?
Acrocentric chromosomes
Describe a Robertsonian Translocation.
Long arm fusion of two acrocentric chromosomes. The fusion chromosome has a single functional centromere.
Which chromosomes are the acrocentric ones?
13, 14, 15, 21, 22
What is the chrom number of a balanced carrier after a Robertsonian Translocation?
45
What happens to the short arm material after a Robertsonian translocation?
It is disgarded.
What is a terminal deletion?
Single break or loss of a terminal broken segment.
What is a interstitial deletion?
Two breaks of one arm and a loss of segment and rejoining of broken arms
What is an isochrone ?
An unbalanced chromosome that is a result of a misdivision at metaphase.
What two clinical syndromes are a result of isochrome formation?
Turner Syndrome,
What is a paracentric inversion?
2 Breaks in the same arm
What is a pericentric inversion?
A break in the P arm and a break in the Q arm.
What differentiates cancer cytogenetics from normal cytogenetics?
- The abnormalities are acquired and restricted to malignant cells.
- Genes are located at break points
- There are hundreds of specific rearrangements.
What type of acquired abnormalities are characteriestic of Cancer Cytogenetics?
Acquired and are both Numerical and Structural
As the malignancy advances what happens to the abnormality of the karyotype?
As the malignancy advances the abnormality of the karotype will advance
