Problem 6 - Biology Today and Tomorrow Without Physiology

Question

Replication of a DNA molecule results in a. a single strand of DNA b. a double-stranded DNA c. two single strands of DNA d. two double strands of DNA

Step-by-Step Solution

Answer

DNA replication results in two double strands of DNA.

Step 1: Understanding DNA Structure

DNA (Deoxyribonucleic Acid) is a double-stranded molecule, forming a double helix structure. Each strand is composed of nucleotides that pair specifically: adenine (A) with thymine (T) and cytosine (C) with guanine (G). This complementary pairing is crucial for DNA replication.

Step 2: Purpose of DNA Replication

DNA replication is the process by which a cell duplicates its DNA before cell division. This ensures that each new cell receives an exact copy of the DNA.

Step 3: Replication Process Overview

During replication, the double-stranded DNA separates into two single strands. Each original strand serves as a template for a new strand, forming two identical double-stranded DNA molecules. Enzymes like DNA polymerase play a critical role in this process.

Step 4: Answering the Question

Considering the replication process, it results in two duplicates of the original double-stranded DNA. Thus, the correct answer is that replication of a DNA molecule results in two double strands.

Key Concepts

DNA structure

DNA, or Deoxyribonucleic Acid, is the fundamental blueprint of life. It is a long molecule made up of smaller units known as nucleotides. Each nucleotide consists of three components: a phosphate group, a sugar molecule, and a nitrogenous base. The structure of DNA is often described as a double helix, which resembles a twisted ladder.

• The sides of the ladder are formed by alternating sugar and phosphate groups.
• The rungs of the ladder consist of nitrogenous base pairs.

Understanding the DNA structure is crucial because it forms the basis of how genetic information is stored and replicated.

double helix

The double helix is the iconic shape that DNA takes, forming a spiral staircase-like configuration. It is stabilized by hydrogen bonds that form between the paired nitrogenous bases. This structure is not just aesthetically pleasing but also incredibly functional.

• The twisting of the strands allows for the compact storage of large amounts of information.
• The helical form facilitates the unwinding process during replication and transcription.

Imagining the double helix can help you better understand how DNA packs into the limited space within a cell nucleus.

nucleotide pairing

Nucleotide pairing is foundational to DNA's ability to replicate efficiently and accurately. Within the double helix, the bases pair in a highly specific manner.

• Adenine (A) pairs with Thymine (T).
• Cytosine (C) pairs with Guanine (G).

This rule of nucleotide pairing is known as **Chargaff's rules**. The complementary base pairing ensures that when DNA replicates, the new strand formed is an exact copy of its counterpart. This specificity is crucial for preserving the integrity of the genetic code through generations.

DNA polymerase

DNA polymerase is a key enzyme in the process of DNA replication. Its main role is to synthesize the new DNA strand by adding nucleotides to the existing chain.

• It reads the template strand and brings in complementary nucleotides.
• DNA polymerase also proofreads the new DNA molecule, ensuring accuracy in base pairing.

Without DNA polymerase, the replication process would lack the precision needed for faithful genetic information transfer. It ensures that each new cell inherits a perfect copy of the DNA, maintaining genetic stability.