To get very long dna-sequences breaked in a senseful way, write in preamble:
\makeatletter
\newcommand\dna[1]{\leavevmode \begingroup
\dnaZ #1\@empty}
\def\dnaZ #1#2{%
#1%
\ifx\@empty#2%
\let\dnaZ\endgroup
\else
\dnaSpace \-%
\fi
\dnaZ #2%
}
\makeatother
\newcommand\dnaSpace{\nobreak\hspace{0pt plus .1pt}}
In your text write it in TeXmode (red) like:
\dna{5'-CCATACAACACCCCCGTGTTCGCCATCAAGAAGAAGGACAGTACCAAATGGAG-3'}
To get colored and counted sequences like

write int the preamble
\usepackage{color}
\makeatletter
\def\DNA#1{% by A. Matthias
\def\@DNA@end{#1}\bgroup\ttfamily
\settoheight\dimen@{I}\advance\dimen@ by 1pt
\edef\htst{\the\dimen@}%
\def\struty{\rule[-.5pt]{\z@}{\htst}}%
\count@=0 \@tempcnta=0 \@tempcntb=0
\fboxrule=0pt \fboxsep=0pt
\noindent\phantom{\@DNA@reserve}\llap 1\
\@DNA
}
\def\@DNA@reserve{0000}% für 4-stellige Zahlen
\def\@DNA@color{'}
\def\@DNA@thecolor{white}
\def\@DNA@setcolor#1{\def\@DNA@thecolor{#1}\@DNA}
\def\@DNA#1{%
\ifnum\count@=10\count@=0\ \fi % Abstand nach 10 Zeichen
\def\@DNA@cmp{#1}%
\ifx\@DNA@cmp\@DNA@end
\let\next\egroup
\else
\ifx\@DNA@cmp\@DNA@color
\let\next\@DNA@setcolor
\else
\advance\count@ by 1
\advance\@tempcnta by 1
\advance\@tempcntb by 1
\ifnum\@tempcnta=51 \\
% Umbruch nach 50 Zeichen
\hskip\z@\phantom{\@DNA@reserve}\llap {\the\@tempcntb}\
\@tempcnta=1
\fi
\colorbox{\@DNA@thecolor}{\struty#1}%
\penalty0\let\next\@DNA
\fi
\fi
\next
}
\makeatother
and the text for example:
\DNA!
ACGT'{red}A CGT'{white}TGCA'{green}x s df'{white}FJKD SLAF DSAIOFDSA
ACGT'{red}ACGT'{white}TGCA'{green}x sdf '{white}FJKDSLAF DSAIOFDSA
AC GT'{red}ACGT'{white}TG CA'{green}xsdf'{white}FJKD SLAF DSAIOFDSA
ACGT'{red}ACGT'{white}T GCA'{green} xs df'{white}FJKDSLA FDSAIOFDSA
ACGT'{red}AC GT'{white}TGCA'{green}xsdf'{white}FJK DSLA FDSAIOFDSA
!
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