Types of histones. Each octamer has two pairs of different histone proteins: H2A, H2B, H3 and H4. They are arranged as a pair of H2A-H2B dimers, and an (H3)2(H4)2 tetramer. There is an additional type of histone, the linker histone H1, which is present in condensed DNA. The C-terminal end is primarily responsible for histone-DNA and histone-histone interactions; 2  The N-terminal consists of a charged, flexible tail which in histones H2B and H3 bury into the minor grooves of DNA, probably to stabilise the interaction.
Hi! I too have heard various opinions about the lifespan of cockatiels. Most say that their *average* lifespan is about 15-20 years. I have several friends who have tiels that are over 25 and still very healthy. Cockatiels can live to be 35 or even older, and are very hardy, sweet birds. They live long lives for a creature so tiny, as most parrots do. Your sweetie may not be so young anymore, but hopefully, with lots of love and a good diet, hopefully he should still have some years left with you.
German cockroach-These generally live for about 3 to 4 months. American cockroach-These can live anywhere from 1 to 2 years. Oriental cockroach-The lifespan of these cockroaches is normally about a year. Surinamcockroach-These cockroaches also live for a year, give or take a month or two. Madeira cockroach-This species generally live for no more than 2 years. Brown-banded cockroach-The lifespan of this species is around 6 months. Madagascan hissing cockroach-These will generally live for about 18 months. Giant Burrowing cockroach-Live in Queensland and they can live for up to 10 years.