7. DNA codes for proteins. But we\'ve learned that there are other types of biol

Question

7. DNA codes for proteins. But we've learned that there are other types of biological molecules besides proteins. Why doesn't DNA code directly for them as well? Why is it enough to code only for proteins? 8. If a particular DNA molecule consisted of 28% guanine-containing nucleotides, what percentages of nucleotides would contain adenine, cytosine, and thymine? 9. A stretch of DNA has the following sequence; 5'-GTAATCGTAGCTTAC-3'. What would the complementary DNA strand be? Be certain to label the 5' and 3' end, and to remember that nucleic acids are always drawn in the 5' to 3' direction. Then provide the mRNA that would be transcribed from this DNA, also indicating the 5' and 3' ends of the RNA molecule. 10. You hear someone say: "DNA produces the proteins in any cell". What is wrong with this statement? Rewrite it into a factual statement.

Explanation / Answer

7. Proteins are polypeptide chains of amino acids arranged in a sequence. The amino acid sequence decides the structure and function of a particular protein. As there are 20 naturally occurring amino acids which have various chemical properties, protein unlocks a variety of functions. The enzymes (proteins) are usually involved in biosynthesis or catabolism of other biological molecules.

Each protein is unique for the sequence of amino acids. However other biomolecules do not posses such specific sequence. Therefore it is logical for DNA to code directly for protein => DNA sequence is transcribed to mRNA which is then translated to protein.

Proteins are required even for DNA replication too. So proteins are the priority as far as function of a cell is concerned.

8. DNA composes four nitrogenous bases: guanine, cytosine, adenine and thymine. Guanine forms triple hydrogen bonding with cytosine while adenine pairs with thymine via double hydrogen bonds. Therefore, number rof guanine equals numberbof cytosine in DNA. The rest are adenine and thymine.

28% be guanine, 28% be cytosine.

Adenine + thymine = (100-28-28) = 44%.

Therefore, Adenine be 22%, thymine be 22% (44/2 = 22).

Related Questions

Navigate

• Browse (All)
• Browse 7
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.