Questions: molecule containing 18% C (cytosine). Based on this information, what would you predict the percent of G (guanine) to be? 18 % 9 % 32 % It cannot be determined 82% Which of the following statements regarding DNA is false? DNA molecules form an anti-parallel double helix. DNA molecules have a sugar phosphate backbone. DNA uses the nitrogenous base uracil. DNA uses the sugar deoxyribose.

Let's address the two parts of the question separately.

Given:

• The molecule contains 18% C (cytosine).

In DNA, cytosine (C) pairs with guanine (G) in a 1:1 ratio. Therefore, the percentage of guanine (G) should be equal to the percentage of cytosine (C).

The answer is $18 \%$.

Let's evaluate each statement:

1. DNA molecules form an anti-parallel double helix.

   • This statement is true. DNA strands run in opposite directions (anti-parallel) and form a double helix structure.

2. DNA molecules have a sugar phosphate backbone.

   • This statement is true. The backbone of DNA is composed of alternating sugar (deoxyribose) and phosphate groups.

3. DNA uses the nitrogenous base uracil.

   • This statement is false. DNA uses thymine (T) as one of its nitrogenous bases, not uracil. Uracil is found in RNA, not DNA.

4. DNA uses the sugar deoxyribose.

   • This statement is true. The sugar in DNA is deoxyribose.

The answer is: DNA uses the nitrogenous base uracil.

1. The percent of G (guanine) is $18 \%$.
2. The false statement regarding DNA is: DNA uses the nitrogenous base uracil.