Polyploidy
3 sets of chromosomes in the nucleus of an organism
Autopolyploidy
Duplication of original genes
Allopolyploidy
Combining the chromosome sets of different species through hybridization
What causes chromosome structure changes
Chromosome breakage, Unequal crossover during meiosis,
What is chromosome breakage
Changes the structure of the chromosome, leading to missed ligation - loss of chromosome segments or deletion, and duplicated ligation, which is the gain of chromosome segments as in duplication
Terminal deletion
loss of a chromosome segment that includes the telomeric region
What happens if a chromosome does not have a centromere
Acentric and loss, as without a centromere, spindle fibres can not connect to the kinetochore and pull it to the other side, leading to an imbalanced chromosome
What is an interstitial deletion
Two break points, and the breakpoints can fuse; however, the fragment that was between those break points ends up being lost. Degrades or no centromere.
How do we detect duplication and deletion
G-banding: if the duplication and deletions are large, then we need to use fish or in situ hybridization. For deletions, one less fluorescence band is observed, and for duplications, one extra fluorescence band is observed, or an unpaired loop.
Chromosome inversion
Structural alteration of a chromosome in which a segment breaks away from the chromosome and subsequently reattaches after 18degrees of 0 rotation
Chromosome Translocation
The relocation of a chromosome or chromosome segment to a non-homologous chromosome is caused by chromosome breakage or incorrect reattachment.
Paracentric Inversion
Centromere does not participate inthe inversion event
Pericentric inversion
The whole centromere is within the inverted region
Inversion Heterozygote
Have one normal and one inverted homolog
How does pericentric inversion influence crossing over and fertility during meiosis
Forms an inversion loop at synapsis, crossing over that occurs within pericentric inversion, resulting in both duplicated and deleted regions in both of the recombinant products. Recombination events yield two viable and two non-viable gametes
How does paracentric inversion influence crossing over.
Any crossover event away from inversion will be fine; however, crossing over within an inverted region will result in duplications and deletions in the recombinant chromosomes.
Translocation
Broken ends of non-homologous chromosomes are reattached. Can be unbalanced when segment breaks and attaches to another, can be reciprocally balanced where we have two breakages and they swap places, and then rovertsonian is when one chromosome has a centromere located at the end of the chromosome, so most gene products are on the long arm.
