Question

a segment of DNA is isolated from a human chromosome. the DNA segment is analyzed and found to contain a total of 100 deoxyribose molecules and 40 adenine bases (among both strands). Which statement must also be true about this DNA segment? It contains 40 thymine bases and 100 phosphate groups It contains 40 thymine bases and 200 phosphate groups It contains 80 thymine groups and 100 phosphate groups It contains 80 thymine groups and 200 phosphate groups

Answer 1

The correct answer is it contain 40 thymine bases and 100 phosphate groups

Step-by-step explanation:

A DNA molecule basically a polymer of deoxyribonucleotides which are linked together by phosphodiester bond.A nuclueotide contain a nitrogen base,deoxyribose sugar and phosphate group.The nitrogen bases form hydrogen bonds with its complementary nitrogen base.

For example adenine forms 2 hydrogen bonds with thymine whereas guanine forms 3 hydrogen bonds with cytosine.

From this point of view it can be stated that if a DNA molecule contain 40 adenine base,these 40 adenine bases will pair with 40 complementary thymine base.

A DNA molecule containing 100 deoxyribose sugar molecules will contain 100 phosphate groups.