If 28% of the bases in a DNA strand are guanine, what percentage are thymine

22%

Explanation:

According to Erwin Chargaff in his complementary base pairing rule, a DNA molecule consists of four nucleotide bases that pair with one another in the follow order: Adenine (A) to Thymine (T), and Guanine (G) to Cytosine (C).

According to Chargaff, the amount of Adenine in the DNA equals the amount of Thymine while the amount of Guanine in the DNA equals the amount of Cytosine. The sum of all the bases equals 100%. That is;

A + T + G + C = 100%

In this question, if 28% of the bases in a DNA strand are Guanine, the amount of Cytosine will also be 28%. Hence,

28% + 28% + A + T = 100

56% + A + T = 100

A + T = 100% - 56%

A + T = 44%

Since, A = T

A/T = 44/2

A/T = 22%

Hence, the amount of Thymine in the DNA strand will be 22%

it has one origin of replication, but it proceeds in two directions - d)

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.