and appears to be more resistant to certain reagents than the secondary wall layers. The lumen wall also called the S3 layer. Dead cotton Dead cotton is a term that refers to unripe cotton fibers that do not absorb dye. Dead cotton is immature cotton that has poor dye affinity and appears as white specks on a dyed fabric. When cotton fibers are analyzed and assessed through a microscope, dead fibers appear differently. Dead cotton fibers have thin cell walls. In contrast, mature fibers have more cellulose and a greater degree of cell wall thickening Genome There is a public effort to sequence the genome of cotton. It was started in 2007 by a consortium of public researchers. Their aim is to sequence the genome of cultivated, tetraploid cotton. "Tetraploid" means that its nucleus has two separate genomes, called A and D. The consortium agreed to first sequence the D-genome wild relative of cultivated cotton (G. raimondii, a Central American species) because it is small and has few repetitive elements. It has nearly one-third of the bases of tetraploid cotton, and each chromosome occurs only once. Then, the A genome of G. arboreum would be sequenced. Its genome is roughly twice that of G. raimondii. Part of the difference in size is due to the amplification of retrotransposons (GORGE). After both diploid genomes are assembled, they would be used as models for sequencing the genomes of tetraploid cultivated species. Without knowing the diploid genomes, the euchromatic DNA sequences of AD genomes would co-assemble, and their repetitive elements would assemble independently into A and D sequences respectively. There would be no way to untangle the mess of AD sequences without comparing them to their diploid counterparts. The public sector effort continues with the goal to create a high-quality, draft genome sequence from reads generated by all sources. The effort has generated Sanger reads of BACs, fosmids, and plasmids, as well as 454 reads. These later types of reads will be instrumental in assembling an initial draft of the D genome. In 2010, the companies Monsanto and Illumina completed enough Illumina sequencing to cover the D genome of G. raimondii about 50x. They announced that they would donate their raw reads to the public. This public relations effort gave them some recognition for sequencing the cotton genome. Once the D genome is assembled from all of this raw material, it will undoubtedly