A fruit fly’s sex is determined predominantly by the number of X chromosomes in each cell.

TLS Online TPP Program

#Id: 391

#Unit 2. Cellular Organization

The H3.H4 tetramer forms the top half of the histone octamer. Histone H3.H4 tetramers occupy a key position in the nucleosome by binding the middle and both ends of the DNA

TLS Online TPP Program

#Id: 392

#Unit 2. Cellular Organization

The two H2A.H2B dimers each associate with 30 bp of DNA on either side of the central 60 bp of DNA bound by H3 and H4.

TLS Online TPP Program

#Id: 393

#Unit 2. Cellular Organization

Using the clock analogy again, the DNA associated with H2A.H2B is located from 5 o’clock to 9 o’clock on either face of the nucleosome disc.

TLS Online TPP Program

#Id: 394

#Unit 2. Cellular Organization

Together, the two H2A.H2B dimers form the bottom part of the histone octamer located across the disc from the DNA ends

TLS Online TPP Program

#Id: 395

#Unit 2. Cellular Organization

Relatively short length (30 bp) of DNA bound by H2A.H2B dimers is not sufficient to prepare the DNA for H3.H4 tetramer binding.

TLS Online TPP Program

#Id: 396

#Unit 2. Cellular Organization

Each nucleosome added to a covalently closed circular template changes the linking number of the associated DNA by approximately –1.2.