Chapter 10: Test 3: Modern Biology Extended Response

Describe how a molecule of DNA is replicated. Include details and vocabulary words associated with each step.

DNA replication is the process by which DNA is copied in a cell before a cell divides. Steps 1. Replication begins with the separation of the DNA strands by helicases. 2. Then, DNA polymerases form new strands by adding complementary nucleotides to each of the original strand 3. Each new DNA molecule is made of one strand of nucleotides from the original DNA molecule and one new strand.

The DNA molecule is described as a double helix. Explain this expression, describe the general structure of a DNA molecule, and describe the bonding in a DNA molecule.

Double helix is the description of the structure of a DNA molecule. A DNA molecule consists of two strands that wind around each other like a twisted ladder. Each strand has a backbone made of alternating groups of sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G), or thymine (T). The two strands are held together by bonds between the bases, adenine forming a base pair with thymine, and cytosine forming a base pair with guanine.

Identify the three types of RNA and describe the function of each.

Messenger RNA (mRNA): a single stranded RNA molecule that carries the instruction from a gene to make a protein. Ribosomal RNA (rRNA): which is part of the structure of ribosomes. Ribosomes are organelles in the cell where protein synthesis occurs. Ribosomes are made of rRNAs and many proteins. Transfer RNA (tRNA): which transfers amino acids to the ribosome to make a protein.