What is meant by the term base pairing?

What does it mean to speak of bases as being complementary?

The DNA from sea urchins contains about 32% A and about 18% G. What percentages of T and C would you expect in sea urchin DNA? Explain.

If a double-stranded DNA molecule is 22% G, what is the percentage of A, T, and C? Explain.

Write the base sequence in a complementary DNA segment if each original segment has the following base sequence:

d. A T A T G C G C T A A A

 If the DNA double helix in salmon contains 28% adenine, what is the percentage of thymine, guanine, and cytosine?

 In DNA, how many hydrogen bonds form between guanine and cytosine?

Write the complementary base sequence for each of the following DNA segments:

c. G G C C T A C C T T A A C G A C G