DNA Structure - base pairing calculations

A certain DNA sequence has 16% adenine. You'd expect ____ guanine in the sequence.

• 8%

• 16%

• 34%

• 84%

• 32%

Answer explanation

A certain DNA sequence has 16% adenine. You'd expect ____ guanine in the sequence.

16% A means there is also 16% T because A-T pair up. That's 32% total.

That leaves 68% left of the DNA, which will be evenly divided between C and G. Half of 68% is 34%.

A certain DNA sequence has 16% adenine. You'd expect ____ thymine in the sequence.

• 8%

• 16%

• 34%

• 84%

• 32%

Answer explanation

A certain DNA sequence has 16% adenine. You'd expect ____ thymine in the sequence.

The amount of adenine (A) is equal to the amount of thymine (T). If A = 16%, then T = 16%.

The amount of adenine + cytosine in a DNA sequence must ...

CHOOSE ALL THAT APPLY

• equal 50% of the sequence

• be greater than the amount of thymine + guanine

• be lower than 25% of the sequence

• equal the amount of thymine + guanine

A certain DNA sequence has 500 total bases. If 100 are guanine, you would expect (a)   to be thymine.

A certain DNA sequence has 500 total bases. If 100 are guanine, you would expect (a)   to be cytosine.

Answer explanation

A certain DNA sequence has 500 total bases. If 100 are guanine, you would expect _______ to be cytosine.

G = C, so 100 guanines means there are 100 cytosines.

A certain DNA sequence has 500 total bases. If 200 are guanine, you would expect (a)   to be adenine.

Which of the following must be true in a DNA sequence?

CHOOSE ALL THAT APPLY

• A = T

• C = A

• A + T = G + C

• A + C = T + G

• A + T > G + C

________ = 0

CHOOSE ALL THAT APPLY

• T - A

• G - C

• (A + T) - (G + C)

• (A + C) - (T + G)

• C - G

A certain DNA sequence has 31% adenine. You'd expect ____ guanine in the sequence.

• 8%

• 19%

• 31%

• 62%

If the amount of cytosine in a DNA sequence is 54%, then you know that ...

• someone didn't count the cytosine right

• guanine is also 54%

• adenine is 46%

• thymine is 4%