Polyploidy
The presence of more than two complete sets of chromosomes in a genome
Autopolyploidy
A pattern of polyploidy produced by the duplication of chromosomes from single genome
Allopolyploidy
A polyploidy organism arising through the union of chromosome sets from different species
Terminal deletion
The loss of a chromosome segment that includes the telomeric region
Interstitial deletion
The loss of a portion of a chromosome from within one arm
Pericentric inversion
A chromosome inversion in which the inverted segment includes the region of the centromere
Paracentric inversion
A chromosome inversion in which the inverted segment does not include the region of the centromere
Dicentric chromosome
A chromosome with two centromeres
Acentric chromosome/fragment
A chromosome fragment without a centromere
Reciprocal translocation
Exchange of chromosome segments between non-homologous chromosomes. If all genes are present, the translocation is “balanced”, but if genes are missing, the translocation is “unbalanced”
Robertsonian translocation
The fusion of two non-homologous chromosomes, often with the deletion of a small amount of non-essential genetic material. Also known as chromosome fusion.
How are chromosomes organized within the nucleus?
Gene rich chromosomes are near the centre, and gene poor chromosomes are near the periphery in chromosome territories
What is G-banding?
Giemsa staining and microscopy to look at chromosomes. Euchromatin are stained lightly by Giemsa, and heterochromatin are stained more heavily by Giemsa. Centromeres are indicated by yellow circles
What are the different ways that an autopolypoid may arise?
- Meiotic whole-genome nondisjuction into a diploid gamete
- Mitotic whole-genome nondisjuction (ND)
- Mitotic and meiotic nondisjuction can also combine
How may have hybridization and genome doubling occured to result in an allopolyploid species?
through hybridization of two organisms, they end up making an offspring that contains both sets of genomes. If the resulting hybrid genome is an odd number, it will double the genome in order to make it even (plants only)
Describe some of the benefits of polyploidization in modern settings
- Bigger fruits
- seedless fruits because fertility is decreased (esp in odd-numbered polypoids)
- Hybrids may outcompete ancestral strains
- rapid speciations
Describe the two main causes of chromosome structure changes
- chromosome breakage, leading to either missed ligation (loss of chromosome segments) or duplicated ligation (gain of chromosome segments
- unequal crossover during meiosis
How does a pericentric inversion, paracentric inversion and balanced translocation impact meiosis?
what types of gametes can be formed and the ratio of viable to unviable
Crossing over that occurs within a paracentric inversion results in both duplicated and deleted regions in both of the recombinant products
2 viable gametes and 2 non-viable gametes
What is nondisjuction?
failure of chromosomes and sister chromatids to properly separate during cell division, and can lead to mosaicism in an individual. Can result in abnormalities in chromosome number and dosage imbalances
In a germline cell this can occur in meiosis I or II
Chromosome inversion
A structural alteration of a chromosome in which a segment breaks away from the chromosome and subsequently reattaches after 180° rotation.
Chromosome translocation
The relocation of a chromosome or chromosome segment to a non-homologous chromosome
