Question

1. students are given data from an investigation that identified some of the chemical elements present in four different samples.

sample elements
1 hydrogen, phosphorus, and nitrogen
2 aluminium, silicon, and copper
3 calcium, potassium, and sodium
4 iron, oxygen, and magnesium
which sample was most likely dna?
a. sample 1 b. sample 2 c. sample 3 d. sample 4

1. each strand of a dna molecule contains nitrogenous bases that pair with other nitrogenous bases in very specific ways. a diagram of a section of dna is shown.

dna strand
3 t g t a g c t g c g c g t 5
which dna strand is complementary to the one shown above?
a. 5 a g u g c u g c g c g u a 3
b. 5 t g t a g c t g c g c g t 3
c. 5 a c a t c g a c g c g c a 3
d. 5 t c g c g c a g c t a c a 3

Explanation:

Step - by - Step Format

Step 1: Recall the elements in DNA

DNA is composed of carbon, hydrogen, oxygen, nitrogen and phosphorus. Sample 1 contains hydrogen, phosphorus and nitrogen which are key elements in DNA.

Step 2: Analyze other samples

Sample 2 has aluminum, silicon and copper which are not major elements in DNA. Sample 3 has calcium and potassium which are not characteristic elements of DNA. Sample 4 has iron which is not a main - component element of DNA.

Answer:

A. Sample 1

Step 3: Recall base - pairing rules in DNA

In DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). The given DNA strand is \(3'\text{-T G T A G C T G C G C G T -}5'\).

Step 4: Determine the complementary strand

The complementary strand will have the bases paired according to the rules. So the complementary strand is \(5'\text{-A C A T C G A C G C G C A -}3'\).