1. The distribution of charged amino acids is H2A (13 K, 13 R, 2 D, 7 E, charge = +17), H2B (20 K, 8 R, 3 D, 7 E, charge = +18), H3 (13 K, 18 R, 4 D, 7 E, charge = +20), H4 (11 K, 14 R, 3 D, 4 E, charge = +18). The total charge of the histone octamer is estimated to be 2 × (17 + 18 + 20 + 18) = +146. The total charge on 150 base pairs of DNA is −300. Thus, the histone octamer neutralizes approximately one-half of the charge.

2. The presence of a particular DNA fragment could be detected by hybridization, by PCR, or by direct sequencing.

3. The total length of the DNA is estimated to be 145 bp × 3.4 Å/bp = 493 Å, which represents 1.75 turns or 1.75 × 2πr = 11.0r. Thus, the radius is estimated to be r = 493 Å/11.0 = 44.8 Å.

4. 5-Azacytidine cannot be methylated. Some genes, normally repressed by methylation, will be active. 5-Azacytidine is also an inhibitor of DNA methyltransferase, resulting in lower levels of methylation and, hence, lower levels of gene repression.

5. Proteins containing these domains will be targeted to methylated DNA in repressed promoter regions. They would likely bind in the major groove because that is where the methyl group is located.

6. Gene expression is not expected to respond to the presence of estrogen. However, genes for which expression normally responds to estrogen will respond to the presence of progesterone.

7. The acetylation of lysine will reduce the charge from +1 to 0. The methylation of lysine will not reduce the charge.

8. On the basis of the pattern of cysteine and histidine residues, this region appears to contain three zinc-finger domains.

9. 10/4000 = 0.25%. 0.25% of 12 Mb = 30 kilobase pairs.

10. Monomethylated-activated; Trimethylated-repressed.

11. The addition of an IRE to the 5′ end of the mRNA is expected to block translation in the absence of iron. The addition of an IRE to the 3′ end of the mRNA is not expected to block translation, but it might affect mRNA stability.

12. The sequences of all of the mRNAs would be searched for sequences that are fully or nearly complementary to the sequence of the miRNA. These sequences would be candidates for regulation by this mRNA.

13. The amino group of the lysine residue, formed from the protonated form by a base, attacks the carbonyl group of acetyl CoA to generate a tetrahedral intermediate. This intermediate collapses to form the amide bond and release CoA.

14. In mouse DNA, most of the HpaII sites are methylated and therefore not cut by the enzyme, resulting in large fragments. Some small fragments are produced from CpG islands that are unmethylated. For Drosophila and E. coli DNA, there is no methylation and all sites are cut.