Question

What do these bands meanregarding DNA packaging?

A.Each histone is 200bp long

B.Each nucleosome contains roughly 200bp of DNA

C.Chromosomes consist of 200bp fragments of DNA that are connected together by histones

D.Genes are 200bp long

Which of the following is not true regarding tightly compacted DNA?

A.Genes present in this area are not likely to be expressed

B.This DNA would be protected from digestion by a nuclease (DNAse)

C.Histone tails on different nucleosomes are likely interacting in this region

D.Histone H1 is present in this region

E.All of the above are true

Answer 1

1 ANS- (B).Each nucleosome contains roughly 200 bp of DNA

The chromatin fibres look like beads on the string , where beads are repeated units of proteins.

The protein associated with DNA are of two types basic proteins ( histone and protamine ) and acidic non -histone chromosomal (NHC) proteins.

The negatively charged DNA molecule wraps around the positively charged histone proteins to form a structure called nucleosome .The nucleosome core is having 4 types of histone protein -,H2A,H2B,H3,H4.

200bp of DNA helix wrap around the nucleosome plugged by H1

Repeating units of nucleosomes form the chromatin in nucleus which is a thread like structure.

Chromatin is packed to form a solenoid structure

Further supercoiling forms a looped structure called chromatin fibre

2 ANS- (E) . All the above are true