The diagrams below illustrate the hierarchical relationship between the MIC and MAC genomes and the genetic views of the two genomes: MIC linkage groups, MAC coassortment groups, and various types of loci mapped (genes, RAPDs and chromosome breakage site polymorphisms).
A. Hierarchical
organization of MIC and MAC genetic maps associated with a chromosome arm
Notes:
- MIC Linkage groups. MIC chromosome arms are the physical basis of linkage groups. Each arm will be eventually represented by a single linkage group, as more loci are mapped.
- MAC Coassortment groups. MAC chromosomes are the physical basis of coassortment groups.
B. Detailed
view of a segment of a linkage group
Additional
Notes:
- Loci names (but not types) are fictitious, but conform to Tetrahymena Genetic Nomenclature.
- Chromosome breakage sites (Cbs). These are the sites at which the ends of MAC chromosomes are generated by site-specific fragmentation of the MIC chromosomes during MAC differentiation. The Cbs is a completely conserved DNA sequence of 15 base pairs, which is necessary and sufficient for chromosome breakage. The two regions flanking a Cbs are named as follows: the "A" region is downstream of the 3' end of the Cbs strand that begins and ends with A, i.e., the 5' AAAGAGGTTGGTTTA 3' strand, while the "T" region is downstream of the 3' end of the complementary Cbs strand, i.e., 5' TAAACCAACCTCTTT 3'. The "A" and "T" regions of a Cbs are specified only in MAC maps. The identification and mapping of every Cbs in the MIC genome and the ends of the two flanking MAC chromosome DNAs is in progress and is the approach by which a physical map of the MIC genome is being constructed.
- Coassortment groups. (B) or (C) indicate strongly biased assortment toward the B or C3 allele, respectively, observed in all members of the coassortment group.
- Genetic Loci. The Catalog contains a detailed description of loci and phenotypes.
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