user37881: I'd like the bottom left text to do the same as the top right, but the randomized text should be limited to "ATCG" in pairs (e.g. "AATTCCGG), instead of numbers. Is there a way to do this with expressions? Preserve Case &  Digits seems to keep the random text to pairs, but I'm not sure how to make an expression so that the pairs are limited to As, Ts, Cs, and Gs. Thanks!



user4426: 
Here's my updated way of doing it.
A couple of points:

This method will only work with fixed width fonts
Make sure you have an even number of characters in your plain text layer.  Add a space on the end if you don't.

Make two identical text layers. In my example, they are labelled "AGCT text" and "plain text".
In the "ACGT text" layer, put the following expression into the Source Text control:
n = 4; // how many pairs of characters (starting from zero, so 0 to 4 is 5 pairs, so 10 characters).
letters = ["A","T","C","G"]; // array of possible characters to use
str = ""; // string we will print

for (i = 0; i <= n; i++){  // start a loop, repeat it n times

    var m = Math.round(random(3)); // pick a number between 0 and 3
    j = letters[m]; // make a variable using one of the characters 
    str += (i > 0 ? "" : "") + j + j; // append that character to the string twice
}

str // print the string

Add a text animator to both layers.
Set the opacity on both text animators to 0%.
In the Advanced settings of the text animator, set the Shape to Square.
Animate the "plain text" animator so that the "Range Selector 1" Start control is 0% at the beginning of the animation, and 100% at the end.  Make sure the "Range Selector 1" End control is set to 100% throughout.
Now animate the "ATCG text" layer:
Set the "Range Selector 1" Start and End controls to 0% at the beginning of the animation.  Set the End control to 100% at the end of the animation. Make sure the Start control is 0% throughout.

37881: <p>I'd like the bottom left text to do the same as the top right, but the randomized text should be limited to &quot;ATCG&quot; in pairs (e.g. &quot;AATTCCGG), instead of numbers. Is there a way to do this with expressions? Preserve Case &amp;  Digits seems to keep the random text to pairs, but I'm not sure how to make an expression so that the pairs are limited to As, Ts, Cs, and Gs. Thanks!
<a href="https://i.stack.imgur.com/uvCcm.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uvCcm.gif" alt="" /></a></p>
<p><a href="https://i.stack.imgur.com/QGyqn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QGyqn.png" alt="preview and timeline" /></a></p>
 4426: <p><a href="https://i.stack.imgur.com/IdX5U.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IdX5U.gif" alt="enter image description here" /></a>
Here's my updated way of doing it.</p>
<p>A couple of points:</p>
<ol>
<li>This method will only work with fixed width fonts</li>
<li>Make sure you have an even number of characters in your plain text layer.  Add a space on the end if you don't.</li>
</ol>
<p>Make two identical text layers. In my example, they are labelled &quot;AGCT text&quot; and &quot;plain text&quot;.</p>
<p>In the &quot;ACGT text&quot; layer, put the following expression into the Source Text control:</p>
<pre><code>n = 4; // how many pairs of characters (starting from zero, so 0 to 4 is 5 pairs, so 10 characters).
letters = [&quot;A&quot;,&quot;T&quot;,&quot;C&quot;,&quot;G&quot;]; // array of possible characters to use
str = &quot;&quot;; // string we will print

for (i = 0; i &lt;= n; i++){  // start a loop, repeat it n times

    var m = Math.round(random(3)); // pick a number between 0 and 3
    j = letters[m]; // make a variable using one of the characters 
    str += (i &gt; 0 ? &quot;&quot; : &quot;&quot;) + j + j; // append that character to the string twice
}

str // print the string
</code></pre>
<p>Add a text animator to both layers.</p>
<p>Set the opacity on both text animators to 0%.</p>
<p>In the Advanced settings of the text animator, set the Shape to Square.</p>
<p>Animate the &quot;plain text&quot; animator so that the &quot;Range Selector 1&quot; Start control is 0% at the beginning of the animation, and 100% at the end.  Make sure the &quot;Range Selector 1&quot; End control is set to 100% throughout.</p>
<p>Now animate the &quot;ATCG text&quot; layer:</p>
<p>Set the &quot;Range Selector 1&quot; Start and End controls to 0% at the beginning of the animation.  Set the End control to 100% at the end of the animation. Make sure the Start control is 0% throughout.</p>
