7. DNA and Chromosome Structure

The principles of complementary base pairing and antiparallel polarity of nucleic acid strands in a duplex are universal for the formation of nucleic acid duplexes. What is the chemical basis for this universality?

For the following fragment of DNA, determine the number of hydrogen bonds and the number of phosphodiester bonds present:

5'-ACGTAGAGTGCTC-3'

3'-TGCATCTCACGAG-5'

The following figure (Figure 1.6) presents simplified depictions of nucleotides containing deoxyribose, a nucleotide base, and a phosphate group. Use this simplified method of representation to illustrate the sequence 3'-AGTCGAT-5' and its complementary partner in a DNA duplex.

How many hydrogen bonds are present in this DNA duplex?

The following figure (Figure 1.6) presents simplified depictions of nucleotides containing deoxyribose, a nucleotide base, and a phosphate group. Use this simplified method of representation to illustrate the sequence 3'-AGTCGAT-5' and its complementary partner in a DNA duplex.

How many phosphodiester bonds are present in this DNA duplex?

The following figure (Figure 1.6) presents simplified depictions of nucleotides containing deoxyribose, a nucleotide base, and a phosphate group. Use this simplified method of representation to illustrate the sequence 3'-AGTCGAT-5' and its complementary partner in a DNA duplex.

What kind of bonds join the C in one strand to the G in the complementary strand?

The following figure (Figure 1.6) presents simplified depictions of nucleotides containing deoxyribose, a nucleotide base, and a phosphate group. Use this simplified method of representation to illustrate the sequence 3'-AGTCGAT-5' and its complementary partner in a DNA duplex.

What kind of bond joins the C to G within a single strand?

Consider the sequence 3'-ACGCTACGTC-5'.

What is the total number of noncovalent bonds joining the nucleotides of the complementary strands?

Consider the sequence 3'-ACGCTACGTC-5'.

What is the total number of covalent bonds joining the nucleotides in each strand?

Consider the sequence 3'-ACGCTACGTC-5'.

What is the double-stranded sequence?

Draw the chemical structure of the three components of a nucleotide, and then link the three together. What atoms are removed from the structures when the linkages are formed?

How are the carbon and nitrogen atoms of the sugars, purines, and pyrimidines numbered?

Human adult hemoglobin is a tetramer containing two alpha (α) and two beta (β) polypeptide chains. The α gene cluster on chromosome 16 and the β gene cluster on chromosome 11 share amino acid similarities such that 61 of the amino acids of the α-globin polypeptide (141 amino acids long) are shared in identical sequence with the β-globin polypeptide (146 amino acids long). How might one explain the existence of two polypeptides with partially shared function and structure on two different chromosomes?

Draw the chemical structure of a dinucleotide composed of A and G. Opposite this structure, draw the dinucleotide composed of T and C in an antiparallel (or upside-down) fashion. Form the possible hydrogen bonds.

Which of the following equations are true for the percentages of nucleotides in double-stranded DNA?

(A)/(G)=(T)(C)