Question

The following sentences describe chromatin structure and how altering chromatin structure can affect gene expression. Complete each sentence using the words provided.

In some cells, DNA combines with proteins to form a substance called

The lowest level of chromatin structure consists of DNA wrapped twice around a group of histones to form a(n)

The formation of nucleosomes may block the binding of transcription factors and RNA polymerase II to the

The structure of chromatin can be modified by altering either the DNA or the attached to DNA.

Large chromatin-remodeling complexes alter the structure of chromatin in order to make the DNA accessible to regulatory proteins which, in turn, affect gene expression.

In vertebrates, methylation of ensures that once a gene is turned off, it stays off.

The of histones is correlated with tighter coiling of the DNA and inactive regions of chromatin.

The of histones tends to loosen the coiling of DNA, making it more accessible for transcription.

Chromatin is present in cells only.

Chromatin that contains highly condensed DNA which is not being expressed is called

Chromatin that contains loosely coiled DNA, which is accessible for transcription, is called

Tighter coiling of the chromatin makes the DNA accessible for transcription.

Answer 1

1. In some cells, DNA combines with proteins to form a substance called chromatin.

2. The lowest level of chromatin structure consists of DNA wrapped twice around a group of histones to form a(n) nucleosome.

3. The formation of nucleosomes may block the binding of transcription factors and RNA polymerase II to the promoter.

4. The structure of chromatin can be modified by altering either the DNA or the histones attached to DNA.

5. Large chromatin-remodeling complexes alter the structure of chromatin in order to make the DNA more accessible to regulatory proteins which, in turn, affect gene expression.

6. In vertebrates, methylation of DNA ensures that once a gene is turned off, it stays off.

7. The methylation of histones is correlated with tighter coiling of the DNA and inactive regions of chromatin.

8. The acetylation of histones tends to loosen the coiling of DNA, making it more accessible for transcription.

9. Chromatin is present in eukaryotic cells only.

10. Chromatin that contains highly condensed DNA which is not being expressed is called heterochromatin.

11. Chromatin that contains loosely coiled DNA, which is accessible for transcription, is called euchromatin.

12. Tighter coiling of the chromatin makes the DNA less accessible for transcription.

Answer 2

DNA combines with proteins to form a structure called chromatin.

The lowest level of chromatin structure consists of DNA wrapped twice around a group of histones to form nucleosome.

The formation of nucleosome may block the binding of transcription factors, and RNA polymerase II to the promoter

The structure of the chromatin can be modified by altering the DNA for the methylation attached to DNA.

Large chromatin remodeling complexes alter the structure of the chromatin in order to make the DNA accessible more to regulatory proteins which in turn effect gene expression.

In vertebrates methylation of DNA ensures that once a gene is turned off it stays off.

The heterochromatin of is histones is correlated with tighter coiling of the DNA and inactive regions.

The   acetylation of histones tends to loosen the coiling of the DNA and inactive regions of the chromosomes.

Chromatin is present in eukaryotic cells.

Chromatin that contains highly condensed DNA, that is not expressed is called heterochromatin.

Chromatin that contains loosely condensed DNA, that is accessible for transcription is called euchromatin.

Tighter coiling of the chromatin makes the DNA less accessible for transcription.

In general terms, there are different levels of chromatin organization:

DNA wraps around histone proteins forming nucleosomes; the "beads on a string" structure called euchromatin.

Multiple histones wrap into a 30 nm fibre consisting of nucleosome arrays in their most compact form heterochromatin