Question

Below is a DNA sequence. Envision that this is a section of a DNA molecule that has separated in preparation for replication, so you are only seeing one DNA strand. Construct the complementary DNA sequence (indicating 5' and 3 ' ends).

Short answer

Construct the complementary DNA strand using base pairing rules, ensuring correct orientation and indicating the 5' to 3' ends on the new strand.

Step-by-step solution

Understanding DNA Replication

During DNA replication, each strand of the original DNA molecule serves as a template for the production of the complementary strand. A DNA strand has a directionality, and the ends of the DNA strand are referred to as 5' (five prime) and 3' (three prime), which signify the carbon numbers in the DNA's sugar backbone. The DNA strand runs antiparallel meaning a 5' to 3' strand will run opposite to a 3' to 5' strand.

Identifying the Complementary Bases

Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G). The sequence provided will have its complementary bases paired accordingly.

Constructing the Complementary Strand

Using the base pairing rule, construct the sequence of the complementary DNA strand by writing down the complementary bases, making sure that the new strand is antiparallel to the given sequence. This means if the original sequence is 5' to 3', your newly constructed strand should be oriented 3' to 5'.

Determine the 5' and 3' Ends

After constructing the complementary strand, remember to indicate the 5' and 3' ends. If the provided strand is 3' to 5', then your newly formed sequence would be 5' to 3' and vice versa.

Key concepts

Complementary DNA Sequence

When delving into the fascinating process of DNA replication, understanding the concept of a complementary DNA sequence is fundamental. DNA replication is the biological process by which a cell duplicates its DNA, and it's crucial for cell division. The double helix structure of DNA means that its two strands are bound together with specific pairs of nucleotides, which are the building blocks of DNA.

During replication, enzymatic machinery in the cell unwinds these strands, and each single strand serves as a template for the creation of its complement. This complementarity refers to the precise pairing of the nucleotides: adenine always pairs with thymine, and cytosine with guanine. To construct a complementary DNA sequence from a given strand, one must add the matching nucleotide for each nucleotide in the original sequence. For example, if the given sequence is 'AGCT,' the complementary sequence would be 'TCGA.'

Complementary sequences are essential in multiple cellular processes, including DNA replication and transcription, the first step in gene expression. A clear conceptual understanding of this key component is crucial for grasping the intricacies of genetics and molecular biology.

5' and 3' ends

The structure of DNA is not just a simple string of nucleotides, but it has directionality and orientation known as the 5' (five prime) and 3' (three prime) ends. These terms reference the carbon atoms of the deoxyribose sugar in the DNA's backbone. The 5' end has a phosphate group attached to the fifth carbon atom, while the 3' end has a hydroxyl (-OH) group attached to the third carbon atom.

What's crucial here is that when DNA replicates, it does so in an 'antiparallel' fashion. This means one strand runs in the 5' to 3' direction, while its complementary strand runs in the opposite 3' to 5' direction. When constructing a new strand, nucleotides are added to the growing strand in the 5' to 3' direction. Understanding this orientation is key for correct DNA replication and for many fundamental molecular biology techniques. Without a grasp of this, one might confuse which end a new nucleotide should be added to during the replication process.

Adenine Thymine Guanine Cytosine Pairing

At the heart of DNA replication lies the base pairing rules. These rules are dictated by the structure and bonding possibilities of the four types of nucleotides: adenine (A), thymine (T), guanine (G), and cytosine (C). Adenine and thymine pair together through two hydrogen bonds, forming an A-T pairing. On the other hand, guanine and cytosine pair through three hydrogen bonds, creating a G-C pairing.

These base pairs are complementary to each other and ensure the DNA strands are a perfect match in shape and form. This specificity in pairing is the reason why the genetic information can be accurately copied during replication. When constructing a complementary strand, it’s a simple yet crucial concept to remember: for every 'A' on one strand there will be a 'T' on the other, and for every 'C' a 'G.' Following this rule does more than just maintain the double helix structure; it is the fundamental principle that preserves the genetic information passed from cell to cell, and generation to generation.