Question: From what direction (i.e. x' end to y' end) is a nucleic acid sequence conventionally defined?
About the article "Nucleic acid sequence", section "Abstract".

Candidate passages:
In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule into a set of consecutive, non-overlapping triplets.
Where these triplets equate to amino acids or stop signals during translation, they are called codons.
A single strand of a nucleic acid molecule has a phosphoryl end, (called the 5′-end) and a hydroxyl, or (3′-end).
These then define the 5'→3' direction.
There are three reading frames that can be read in this 5'→3' direction, each beginning from a different nucleotide in a triplet.
In a double stranded nucleic acid, an additional three reading frames may be read from the other, complementary strand in the 5'→3' direction along this strand.
As the two strands of a double stranded nucleic acid molecule are antiparallel, the 5'→3' direction on the second strand corresponds to the 3'→5' direction along the first strand.
In general, at most one reading frame in a given section of a nucleic acid is biologically relevant.
Viral transcripts can be translated using multiple reading frames. 
Dda is a molecular motor, specifically a helicase that moves in the 5' end to 3' direction along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands, using the free energy released by the hydrolysis of adenosine triphosphate.
The National Center for Biotechnology Information (NCBI) Reference Sequence accession number is NP_049632. 
A nucleic acid sequence is a succession of letters that indicate the order of nucleotides within a DNA (using GACT) or RNA (GACU) molecule.
By convention, sequences are usually presented from the 5' end to the 3' end.
Because nucleic acids are normally linear (unbranched) polymers, specifying the sequence is equivalent to defining the covalent structure of the entire molecule.
For this reason, the nucleic acid sequence is also termed the primary structure.
The sequence has capacity to represent information.
Biological DNA represents the information which directs the functions of a living thing.
In that context, the term genetic sequence is often used.
Sequences can be read from the biological raw material through DNA sequencing methods.
Nucleic acids also have a secondary structure and tertiary structure.
Primary structure is sometimes mistakenly referred to as "primary sequence".
Conversely, there is no parallel concept of secondary or tertiary sequence.
The convention for a nucleic acid sequence is to list the nucleotides as they occur from the 5' end to the 3' end of the polymer chain, where 5' and 3' refer to the numbering of carbons around the ribose ring which participate in forming the phosphate diester linkages of the chain.
Such a sequence is called the primary structure of the biopolymer. 
Nucleic acid thermodynamics is the study of how temperature affects the nucleic acid structure of double-stranded DNA (dsDNA).
The melting temperature ("Tm") is defined as the temperature at which half of the DNA strands are in the random coil or single-stranded (ssDNA) state.
"Tm" depends on the length of the DNA molecule and its specific nucleotide sequence.
DNA, when in a state where its two strands are dissociated (i.e., the dsDNA molecule exists as two independent strands), is referred to as having been denatured by the high temperature.