Defenitions for biology terms

[pre_vet_gal]

I need help defining these terms, I am unable to find them in my book, please if you can help, I would be greatful! Thanks!

1. Diploid number of organisms

2. Importance of histones

3. root meristem

thanks!

[James]

The diploid number for an organsim is the number of chromosomes an organism has in one of it's body cells, as opposed to a gamete which has half (haploid number) of chromosomes. For humans the diploid number would be 46.

Histones are proteins 'wound around' the chromatin, to make chromosomes,which not only give stuctural support, but also take part in regulating access to the genes

A meristem is the part at the tip of a plant shoot or root that causes the shoot or root to increase in length.

[Jelanen]

Couple clarifications. Ploidy varies by species. Humans are 2n (meaning we have 2 of each autosome) some things are 1n. Plants get really crazy...some are 4n or more.

The interactions between proteins and DNA can be very complex and nomenclature can make the difference between confusion and understanding. Chromatin is the complex of DNA and chromosomal proteins Histones are proteins that DNA loops around. Primarily (from my perspective), the histone-DNA interaction helps in packing all that genetic material into a small space. Histones also contribute to the position of DNA within the nucleus. Every part of every chromosome has a particular location inside the nucleus where it is supposed to be. Think of it like a three dimensional address. Histones and other non-histone proteins provide this structure.

As for the meristem....I'm a molecular biologist, not a botanist...I forgot all my plant stuff after the exam.

-Jelanen