Chromosome Rearrangements Flashcards
What type of mutations arise due to errors in double strand break repair mechanisms?
Deletions, duplications, inversions, and translocations.
What type of mutations arise due to errors in recombination?
Deletions, duplications, inversions, and translocations.
What is fluorescent in situ hybridization?
A technique for illustrating deletions or duplications in chromosomes.
How does fluorescent in situ hybridization (FISH) work?
The chromosome to be investigated is denatured using heat or a base to form single stranded DNA. Fluorescently labelled DNA with the sequence of deletion or duplication in question is created, and this sequence will hybridize with the single stranded DNA if it is present. Thus, the absence of fluorescence indicates a deletion while more fluorescence than predicted indicates a duplication.
Describe the process of chromosome banding.
Lymphocytes from the blood are grown in vitro and treated with colchine to prevent spindles from attaching to condensed chromosomes. These condensed chromosomes are fixed with trypsin (protease) and Giemsa (stain). This creates banding patterns where homologous chromosomes have similar banding patterns.
What is a deletion loop?
A region of DNA that forms a loop such that, during replication, the sister chromatid is synthesized lacking the loop.
What is a pericentric inversion?
An inversion in DNA where the centromere is part of the inverted region.
What is a paracentric inversion?
An inversion in DNA where the centromere is not a part of the inverted region.
What does it mean if a gamete is balanced?
The gamete contains one complete haploid set of genes (order doesn’t matter).
What does it mean if a gamete is unbalanced.
The gamete is either deficient for some genes and/or duplicated for other genes.
What fraction of gametes will be balanced v.s. unbalanced if a chromosome with a pericentric inversion undergoes meiosis?
Half of the gametes will be balanced while the other half will be unbalanced assuming only single crossovers occur.
What fraction of gametes will be balanced v.s. unbalanced if a chromosome with a paracentric inversion undergoes meiosis?
Half of the gametes will be balanced while the other half will be unbalanced assuming only single crossovers occur. Of the unbalanced gametes, half will be acentric (lacking a centromere) while the other half will be dicentric (having two centromeres).
What are reciprocal translocations?
Translocations where parts of two non-homologous chromosomes are exchanged with no net loss of genetic information.
Describe the process of spectral kayrotyping.
Chromosomes are sorted by means of fluorescence activated cell sorting (flow sorting) and labelled using FISH. The parts belonging to each chromosome can then be tracked for translocations that may later occur.
Do translocation homozygotes have decreased fertility?
No, despite there being a translocation, since this occurs in both homologous chromosomes, meiosis is not affected.
