Complementary base sequence

Complementary Base Sequence

In molecular biology, a complementary base sequencerefers to the sequence of nucleotides in a nucleic acid strand that can form hydrogen bonds with another nucleic acid strand, following the rules of base pairing. This concept is fundamental to the structure and function of DNA and RNA, as it underlies the mechanisms of replication, transcription, and translation.

Structure of Nucleic Acids

Nucleic acids, such as DNA and RNA, are polymers made up of monomers called nucleotides. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. The sequence of these bases encodes genetic information.

DNA

DNA, or deoxyribonucleic acid, is a double-stranded molecule. The two strands are held together by hydrogen bonds between complementary bases. The base pairing rules for DNA are:

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

This means that if one strand of DNA has the sequence 5'-ATCG-3', the complementary strand will have the sequence 3'-TAGC-5'.

RNA

RNA, or ribonucleic acid, is typically single-stranded, but it can form double-stranded regions through complementary base pairing. The base pairing rules for RNA are similar to those for DNA, with one key difference:

- Adenine (A) pairs with Uracil (U) instead of Thymine (T) - Cytosine (C) pairs with Guanine (G)

Function in Replication and Transcription

Complementary base sequences are crucial for the processes of DNA replication and transcription.

DNA Replication

During DNA replication, the double helix is unwound, and each strand serves as a template for the synthesis of a new complementary strand. DNA polymerases add nucleotides to the growing strand by matching them with the complementary bases on the template strand.

Transcription

In transcription, a segment of DNA is used as a template to synthesize a complementary RNA strand. The RNA polymerase enzyme reads the DNA template strand and incorporates the appropriate ribonucleotides to form the RNA transcript.

Role in Genetic Code and Translation

The genetic code is read in sets of three nucleotides, called codons, during the process of translation. Each codon specifies a particular amino acid. The complementary base pairing between the mRNA codons and the anticodons of tRNA molecules ensures the correct sequence of amino acids in a protein.

Also see

• Base Pair
• DNA Replication
• Transcription (genetics)
• Translation (biology)
• Genetic Code