100 points!

1st question:
if a strand of dna is gcgaga what is the complementary mrna code?

a: cgctct

b: tatgcg

c: cgcucu

d: cccuuu

2nd question:
select the answer below that is the correct elemental makeup of nucleic acids.

a: c, h,o

b: c, h,o in a 1: 2: 1 ratio

c: c, h,o, n

d: c, h,o, n,p

1. C

2. D

Explanation:

QUESTION 1:

Transcription is one of the processes of gene expression in which the genetic information in a DNA strand is copied into an mRNA, which conveys it out of the nucleus for protein synthesis. Transcription involves making a complementary strand of mRNA from a DNA template. In transcription, an enzyme called RNA polymerase adds nucleotides to the mRNA strand using the complementary base pairing rule.

Complementary base pairing rule, as postulated by Chargaff, is a phenomenon whereby in DNA, Guanine (G) always binds to Cytosine (C) in an hydrogen bond while Adenine (A) binds to Thymine. i.e A-T, G-C. The RNA polymerase synthesizes a complementary strand of the DNA nuceotide it reads i.e. if it reads Adenine, it synthesizes Uracil and if it reads Guanine, it synthesizes Cytosine and vice versa.

Note that, in the nearly made RNA strand, Uracil replaces Thymine.

So in this case, a DNA strand containing nucleotides GCGAGA, the RNA polymerase will synthesize nucleotides CGCUCU in the mRNA strand.

QUESTION 2:

Nucleic acids are polymers made up of monomers called nucleotides. In nature Deoxyribosenucleic acid (DNA) and ribosenucleic acid (RNA) are referred to as nucleic acids. This nuceotide is made up of three components viz: 5-carbon sugar (Ribose and Deoxyribose), Phosphate group, and a Nitrogenous base (Adenine, Guanine, Cytosine and Thymine/Uracil).

Looking critically at the structure of each component;

1. Ribose and Deoxyribose (lacks one oxygen atom), are pentose sugars i.e have five carbons. Their structure is made up of Carbon, Hydrogen and Oxygen just like all sugars.

2. Nitrogenous bases are organic molecules with a nitrogen atom having the chemical properties of a base. They are five including Adenine, Guanine, Cytosine, Thymine (DNA) and Uracil (RNA). Since they are organic molecules, they also possess C, H and O in their structure with addition of Nitrogen (N).

3. A phosphate group is a phosphorus atom bound together in a covalent bond to four negatively charged oxygen atoms i.e PO4(3- ). It has a P and O atoms in its structure.

Hence, collating the various elements that make up the building blocks (nucleotides) of nucleic acids, we have C, H, O, N and P

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