Question

1)The histone proteins of nucelosomes are often abnormally modified in cancer cells, leading to _____. a. an alteration in chromatin structure b. an alteration in levels of transcription c. double-stranded breaks in DNA d. All of the above e. Both a and b

2)

A DNA strand contains the sequence TCGGATGCACCT. A mutation happened that results in the sequence TCCGGATGCACCT. What type of mutation does this change represent?

		a point mutation
		a missense mutation
		frameshift mutation
		a silent mutation

3)

Chromosomal rearrangements might position a gene near heterochromatin. The gene's transcription

		may be inverted.
		may be amplified.
		may cease.
		will turn on.

Answer 1

Answer 1) E

Histone proteins are found in the core of nucleosome. It helps to wrap the DNA around it. When there is found mutation in the histone proteins, then there is not found wrapping of DNA around the histone. Hence the chromatin structure is changed. The DNA becomes loosely wound. In this way, RNA polymerase interacts with the promoter. Hence there is found alteration of transcription.

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Answer 2) frameshift mutation.

The C is inserted in the wild type sequence after C. This leads to change the whole sequence of DNA. Hence mRNA codon sequence is also changed. That's why this us the case of frameshift mutation.

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Answer 3) may cease.

When the chromosome rearrangement occurs near the heterochromatin region, then there is not found any expression of genes. Because heterochromatin region is transcriptionally inactive in nature. RNA polymerase does not interact with promoter. Hence there is not found any expression of rearranged genes.

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