Bio-Pac 05: Objective 01-03

Question 1

Objective 1. In a drawing label the following parts of a DNA molecule: phosphate group, deoxyribose sugar molecule, nitrogen carrying bases, nucleotide, double helix, strong chemical bond, and hydrogen bond

Answer 1

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Question 2

Objective 2. List and describe the steps of DNA replication.

Answer 2

DNA replication begins with the separating of two DNA strands or the breaking of weak bonds. Then a complex series of enzyme-catalyzed reactions occurs, and complementary nucleotides from the cytoplasm bond to the expose bases of the original DNA strand and to each other. Each original strand of DNA comes to be bonded to a new complementary strand of DNA. The original strands act as templates, or patterns, on which the new strands of DNA form. There are now two identical DNA molecules that exist.

Question 3

Objective 3. List four ways RNA is different from DNA.

Answer 3

RNA is the second kind of nucleic acid and it helps make proteins. RNA is composed of a single strand of nucleotides. RNA contains the sugar molecule ribose instead of the sugar molecule deoxyribose. RNA has four nitrogen bases but instead of thymine it contains uracil. RNA is the form in which information moves from DNA in the nucleus to the ribosomes in the cytoplasm. Enzymes make an RNA copy of a DNA strand in a process called transcription. The process of RNA replication is similar to the replication of DNA but the replication of RNA produces a single stranded RNA molecule. The RNA copy that carries the information out into the cytoplasm of the cell is the messenger RNA (mRNA). THE mRNA carries the information for making a protein chain to the ribosomes where proteins are synthesized. The portions of the DNA code for RNA that makes up ribosomes is called ribosomal RNA (rRNA)—it helps produce enzymes needed to bond amino acids together during protein synthesis. The process of converting the information in a sequence of nitrogen bases in mRNA into a sequence of amino acids that make up protein is known as translation. Translation, which occurs on ribosomes, involves a third RNA. If proteins are needed to be built, the 20 different amino acids dissolved in the cytoplasm must be brought to the ribosomes, so the Transfer RNA (tRNA) brings the amino acids to the ribosomes so they can be assembled in proteins. Correct translation of the code depends upon the joining of each mRNA codon (a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule or amino acid) with the anticodon (a sequence of three nucleotides forming a unit of genetic code in a transfer RNA molecule, corresponding to a complementary codon in messenger RNA) of the proper tRNA molecules