Frequently Asked Questions

How large is the maize genome?

Estimates for the sizes of genomes of different maize species can vary quite dramatically from about 2.3 to 3.3 Gb. It has been suggested that the difference is mainly due to the amount of heterochromatin in forms of the number of knobs or B chromosomes. These estimates are based on microdensitometry of Feulgen-stained, root-tip prometaphase cells (Laurie, D and Bennett, MD. 1986. MNL 60:31-32). Based on the agarose DNA fingerprinting of the three BAC libraries of inbred B73 its size has been estimated to have a physical length of 2.365 GB. Therefore, it appears that inbred B73 represents the low end of the range of genome sizes within the Zea species. Based on an average insert size of 150 kb, the redundancy of the BAC libraries has been calculated to be 29-fold. This was confirmed by hybridizing filters of the library with unique gene probes. The number of positive clones correlated well with a redundancy of clones of a 2.3 Gb large genome (Yim et al. 2002. Plant Physiology 130:1686-1696).

What maize strain have we chosen for sequencing? And why?

How many chromosomes does maize have?

Is maize diplod on polyploid?

How many corn genomic libraries are being used for sequencing?

The following table displays information on the genomic libraries used for sequencing:

Zea mays ssp. mays cv. B73 BAC Libraries
No Library Made By No. of BACs 384-well Plates BACs with No Inserts Empty Wells Average Insert Size Genome Equivalent* Genomic DNA Partially Digested with Cloned into Vector size (bp) Anti-biotic End Seq by
1 ZMMBBb (NSF B73) Jeff P. Tomkins, CUGI 247,680 1 to 645 991 (0.4 %) ? 136 kb 14.2x HindIII HindIII site of pCUGI Chloram-phenicol T7, SP6
2 ZMMBBc (CHORI 201) Pieter J. de Jong, CHORI 110,592 1 to 288 0 (0%) 3,955 (3.6 %) 163 kb 7.6x EcoRI + EcoRI Methylase EcoRI site of pTARBAC2.1 13,397 Chloram-phenicol T7, SP6
3 110,592 289 to 576 2,375 (2.1 %) 2,638 (2.4 %) 167 kb 7.8x MboI BamHI site of pTARBAC1.3 13,462 Chloram-phenicol T7, SP6
TOTAL 468,864 1,221 3,366 (0.7%) 6,593 (1.4 %) 150 kb 29.6x
Effective Figure of BACs (Minus empty wells and without insert) 464,277 *Genome Coverage (Based on 2,365 Mb Coverage by Agarose fpc)

Who is Yum Kax?