Chromosomal Abnormalities (Megee L2, 3) Flashcards
Give some examples of events that induce double strand breaks in the DNA
Ionizing radiation
Meiotic recombination
DNA repair mechanisms can induce double strand breaks
What has to happen (structurally) for a chromosomal rearrangement to take place?
two double strand breaks
List some results of DSB’s that occur during meiotic recombination
duplications deletions insertions inversions translocations
Where do the breakpoints of duplications, deletions, insertions, translocations and inversions all seem to occur?
Within regions of the chromosome composed of a lot of repeated sequences.
What are the two main categories of chromosomal structural rearrangements?
Balanced and Unbalanced
What is a balanced rearrangement?
Normal compliments of the genetic material but with varying stability during meiosis and mitosis
Give some examples of balanced rearrangements.
Inversion
Reciprocal Translocation
Robertsonian Translocation
Describe an inversion rearrangement.
Two double strand breaks on the same piece of DNA. The disconnected sequence is inverted before being reinserted and reconnected.
What is a paracentric inversion?
What is a pericentric inversion?
Paracentric: The removed, inverted and reinserted piece does NOT include the centromere.
Pericetric: The removed, inverted and reinserted piece DOES include the centromere.
Describe a reciprocal traslocation rearrangement.
Two non-homologous chromosomes basically each swap a piece of their DNA for a piece from the other chromosome. ex: 12345 12389 ----> 6789 6745
In pericentric inversions, crossovers within the inverted region can produce _________ and ________.
deletions and duplications.
In pericentric inversions, crossovers NOT within the inverted region will produce ____________ gametes.
balanced (full chromosomal compliment with the inversion)
In paracentric inversions, crossovers within the inverted region can produce _________ and ________.
dicentric and acentric
Individuals with balanced chromosomal rearrangements are “likely” to be ________.
phenotypically normal…but it really depends on the specific rearrangement
Suppose an individual has a reciprocal translocation in their chromosomes. At anaphase, a __________ figure is formed and segregation can be _______, _______ or ________.
quadravalent
alternative (normal or balanced)
adjacent 1 (unbalanced)
adjacent 2 (unbalanced)