Which statement best describes replication?
1) RNA is produced from DNA
2) Protein is produced from DNA
3) DNA is produced from RNA
4) Protein is produced from RNA
5) DNA is copied
The correct answer and explanation is:
The correct answer is 5) DNA is copied.
Explanation:
Replication is the process by which DNA makes a copy of itself. This is essential for cell division, allowing each daughter cell to inherit an identical copy of the genetic material. The process begins at specific locations on the DNA molecule called “origins of replication.” The enzyme helicase unwinds the double helix, creating two single-stranded templates. Each of these strands then serves as a template for synthesizing a new complementary strand.
The enzyme DNA polymerase plays a key role in adding the appropriate nucleotides (adenine, thymine, cytosine, guanine) to the growing strand, following the base pairing rules: adenine pairs with thymine, and cytosine pairs with guanine. This process results in two identical DNA molecules, each composed of one old (parental) strand and one newly synthesized strand, a process known as semiconservative replication.
In addition to DNA polymerase, other enzymes are involved in replication. For example, primase synthesizes short RNA primers to provide a starting point for DNA polymerase. Ligase helps seal the gaps between the newly synthesized DNA fragments, ensuring the strands are continuous. Replication occurs in both directions from the origin, and at each replication fork, one strand is synthesized continuously (leading strand) while the other strand is synthesized in fragments (lagging strand).
Replication is an incredibly accurate process, but mistakes can happen, leading to mutations. Cells have various repair mechanisms to correct errors in the newly synthesized DNA, ensuring the integrity of the genetic material is maintained. Replication is a crucial step in the life cycle of cells and is tightly regulated to prevent errors that could lead to diseases such as cancer.