Missed a pretty important bit

assets/site.css

@@ -26,7 +26,6 @@ body {
 }
 
 h1,
-h2,
 p {
 	font-weight: 400;
 }
@@ -52,10 +51,6 @@ h1 {
 	text-align: center;
 }
 
-h2 {
-	font-size: 1rem;
-}
-
 pre {
 	font-size: 16px;
 	font-family: var(--font-mono);
@@ -166,4 +161,5 @@ i.cite {
     display: block;
     text-align: center;
     padding-top: 8px;
+    font-size: 9pt;
 }

pages/simplest-circuit.md

@@ -16,7 +16,7 @@ So, how many proteins there are, with no variables, depends on how many proteins
 
 Now, the circuit. This circuit is the simplest possible circuit: a single gene — let's call it \\(x\\) — coding for a single protein \\(p\\) at a rate of \\(\beta\\) molecules per unit time.
 
-![alt text](/assets/simplest-circuit-dg1.png)
+![A diagram of the simplest possible circuit, with one gene coding for one protein.](/assets/simplest-circuit-dg1.png)
 <i class="cite">Credit: CalTech</i>
 
 However, in real life, proteins aren't just made forever; they're also reduced, through both _active degradation_ (being broken down) and _dilution_ (the cell getting bigger, which reduces the protein's _concentration_). That's represented above by the dashed circle. For simplicity, let's say that it's being reduced at a rate constant \\(\gamma\\) (that letter is a gamma, for anyone who wanted to know). Note that this is not just a rate &mdash; it's a _rate constant_, meaning that the actual rate is proportional to the number of molecules. More molecules, more reduction.
@@ -55,16 +55,58 @@ $$f(t)=xt=\frac{\beta t}{\gamma}$$
     </div>
 </div>
 
-It's a line &mdash; for now. Onwards!
+It's a line &mdash; for now.
+
+## Considering Transcription
+
+Right now, we have protein synthesis as one process &mdash; no intermediate steps. In reality, it has two: transcription and translation. The mRNA made in transcription can _also_ be degraded and diluted, just like the proteins made in translation. Let's add another variable to represent mRNA &mdash; call it \\(m\\). This can be shown in a diagram:
+
+![The simplest circuit, now considering both transcription and translation, with mRNA (m) being produced and reduced.](/assets/simplest-circuit-dg2.png)
+<i class="cite">Credit: CalTech</i>
+
+The reaction can now be described by two coupled differential equations:
+
+$$\frac{dm}{dt} = \beta_m - \gamma_mm$$
+$$\frac{dx}{dt} = \beta_pm - \gamma_px$$
+
+Now, to find steady-state mRNA and protein concentrations, we set both derivatives to zero and solve, giving us:
+
+$$m_{ss}=\frac{\beta_m}{\gamma_m}$$
+$$x_{ss}=\frac{\beta_pm_{ss}}{\gamma_p}=\frac{\beta_p\beta_m}{\gamma_p\gamma_m}$$
+
+This tells us that steady-state protein concentration, when we consider transcription and translation as separate steps, is proportional to the product of the two synthesis rates and inversely proportional to the product of the two degradation rates. Again, if you think about it, that's pretty intuitive.
+
+Here's a graph to play with:
+
+<div class="graph">
+    <div id="concentration-graph-2step"></div>
+    <div>
+        <label for="betap">β<sub>p</sub></label>
+        <input type="range" id="betap">
+        <label for="gammap">γ<sub>p</sub></label>
+        <input type="range" id="gammap">
+    </div>
+    <div>
+        <label for="betam">β<sub>m</sub></label>
+        <input type="range" id="betam">
+        <label for="gammam">γ<sub>m</sub></label>
+        <input type="range" id="gammam">
+    </div>
+</div>
+
+Onwards!
 
 <nav-links back="/concepts.html"></nav-links>
 
 <script>
     plot('#concentration-graph', (beta, gamma) => `(${beta}x)/${gamma}`, ['#beta', '#gamma'])
+    plot('#concentration-graph-2step', (betap, gammap, betam, gammam) => `((${betap})(${betam})x)/((${gammap})(${gammam}))`, ['#betap', '#gammap', '#betam', '#gammam'])
     defineVars([
-        ['γ', 'The rate constant for reduction of protein concentration.'],
+        ['γ', 'The rate constant for reduction of concentration.'],
-        ['β', 'The rate of protein production, in molecules per unit time.'],
+        ['β', 'The rate of production, in molecules per unit time.'],
         ['x', 'The gene in question.'],
-        ['p', 'The protein in question.']
+        ['m', 'The mRNA in question.'],
+        ['p', 'The protein in question.'],
+        ['ss', 'steady-state']
     ])
 </script>