Imagine repeating the experiment on epigenetic inheritance that is shown in Figure 19.6. You measure the amount of radioactive uridine (U) incorporated into Hnf4a mRNA in counts per minute (cpm) to determine the level of Hnf4a gene transcription in rats born to mothers fed either a normal diet or a low-protein diet. The results are 11,478 cpm for the normal diet and 7368 cpm for the low-protein diet. For this problem, your task is to prepare a graph similar to the one at the bottom of Figure 19.6 that shows the normalized results for the low-protein diet relative to the normal diet. Normalizing values means that the value obtained from one condition is expressed as 1.0 (the norm; the normal diet in this case) and the values obtained from any other conditions (low-protein diet in this case) are expressed as decimal values relative to the norm.

Verified step by step guidance

1. Step 1: Understand the concept of normalization. Normalizing values means expressing one condition as a baseline (1.0) and other conditions as decimal values relative to the baseline. In this case, the normal diet transcription level (11,478 cpm) will be set as 1.0, and the low-protein diet transcription level (7,368 cpm) will be expressed relative to it.
2. Step 2: Use the formula for normalization: Normalized value = (Value from condition of interest) / (Baseline value). For the low-protein diet, divide 7,368 cpm by 11,478 cpm to calculate the normalized value.
3. Step 3: Prepare the graph. On the x-axis, label the two conditions: 'Normal Diet' and 'Low-Protein Diet.' On the y-axis, label 'Normalized Hnf4a Transcription Levels.' The normal diet will be represented as 1.0, and the low-protein diet will be represented as the calculated decimal value.
4. Step 4: Plot the data. Draw a bar graph with two bars: one for the normal diet (height = 1.0) and one for the low-protein diet (height = the normalized value). Ensure the bars are clearly labeled and include error bars if applicable.
5. Step 5: Add a title and legend to the graph. Title the graph 'Normalized Hnf4a Transcription Levels in Offspring of Mothers Fed Different Diets.' Include a legend or note explaining that the normal diet is set as the baseline (1.0) and the low-protein diet is expressed relative to it.

Key Concepts

Epigenetic Inheritance

Epigenetic inheritance refers to the transmission of genetic information that is not encoded in the DNA sequence itself but rather through chemical modifications that affect gene expression. These modifications can be influenced by environmental factors, such as nutrition, and can be passed from one generation to the next, potentially affecting the phenotype of offspring without altering the underlying genetic code.

Normalization of Data

Normalization of data is a statistical technique used to adjust values measured on different scales to a common scale, often to facilitate comparison. In this context, the transcription levels of Hnf4a mRNA from rats on a low-protein diet are expressed relative to those on a normal diet, allowing for a clearer understanding of the impact of diet on gene expression by setting the normal diet as a baseline (1.0).

Histone Modifications

Histone modifications are chemical changes to the histone proteins around which DNA is wrapped, influencing the structure of chromatin and thereby regulating gene expression. These modifications can either promote a condensed form of chromatin, which is generally associated with gene silencing, or a decondensed form, which is associated with active transcription. The study examines how maternal diet affects these modifications and subsequent gene transcription in offspring.