A collection of blog posts connected to my teaching on biomedical sciences and biochemistry degrees. All views and opinions expressed are my own, and not connected to my past, present or future employers.
In this video, I look at how, after the haploid sperm fuses with the haploid oocyte to form a zygote, we go from one diploid cell to over 200 different cell types and 3 times 10 to the power of 13 (3 with 13 zeros after it) cells. That is a lot of cells and the process is called cellular differentiation.
OK, so that is a wrap on DNA, a topic of immense significance in the world of biology and genetics.
Over the past few weeks, I have released fourteen revision videos on DNA, with accompanying posts on here and with information sheets accompanying each video (you can find a link to the information sheets in the links below).
In the videos, I have covered:
DNA and Genes - I looked at how many genes does a human have? Do we have more genes than a plant? Do larger organisms, such as trees, have more genes than humans?
In this video, I look at Nucleic Acid Hybridisation and how it is the underlying principle for several lab techniques, such as PCR (Polymerase Chain Reaction), dot blots, colony blot hybridisation, chromosome in situ hybridisation (FISH), microarrays, Southern and Northern blotting, and CRISPR/Cas9 gene editing.
How do scientists determine the size of DNA bands on an agarose gel? In this guide, I will walk you through the step-by-step process of calculating the size in base pairs of a DNA band on an agarose gel.
Blog Bonus: Free information sheet summarising the video and the steps - download.
Introduction
When working in a lab and running an agarose gel, you may need to determine the size of the DNA fragment, and this information may be crucial for various biological research applications.
This approach is also described in the following video:
Setting Up the Experiment
Imagine you have loaded a DNA ladder with known sizes in one lane and your DNA sample with an unknown size in another lane of the gel and you get a result that looks like this when the gel has been run.
Before you can calculate the size of your DNA band, you must first label the gel and collect data to create a calibration curve.
Data Collection and Analysis
By measuring the distances the DNA bands in the ladder (see below) have moved and plotting the log values of their sizes against the distances travelled in millimetres (or you can do it in pixels), you can create a calibration curve. This curve will help you accurately determine the size of the DNA band in your unknown sample.
The image below shows the gel and the data table for the plot.
From the table, you plot the calibration curve.
Calculating the Size of the DNA Band
After plotting the calibration curve (above) and identifying the distance your unknown band has travelled, you can use the curve to determine the size of the DNA band in base pairs. By following a simple formula involving logarithms, you can convert the log value to the actual size in base pairs.
Conclusion
Calculating the size of a DNA band on an agarose gel requires careful data collection, analysis, and interpretation. By following the steps outlined in this guide, you can confidently determine the size of DNA fragments in your samples.
In this video, I examine the step-by-step process of cloning DNA into plasmids and address common challenges faced in the lab. I start by preparing the DNA and then move on to using restriction enzymes like EcoRI and HindIII. I explain the importance of choosing the correct enzyme pairs to prevent self-ligation and ensure the correct orientation of the insert. I also cover the blue-white selection method to verify successful cloning and discuss using different vectors for larger DNA segments.
In this video, I give a brief introduction to the subject of DNA cloning.
DNA cloning is an important lab skill that all life and biomedical science students should possess. In the video, I provide a summary of in vivo and in vitro cloning, along with the key steps, tools and methods you would use.
I have just posted a video that looks at the complex processes of gene regulation and protein production within cells. In the video, I explore six key stages where cells regulate protein synthesis, ensuring precise protein production according to cellular needs. These stages include:
Transcriptional Control: The initiation of RNA production and the involvement of transcription factors.
RNA Processing: The conversion of pre-messenger RNA to mature mRNA, including splicing and editing.
Transport and Localisation: The transportation of mRNA to the correct cellular locations for protein synthesis.
Translational Control: Regulation of mRNA translation within the cellular environment.
RNA Degradation: Mechanisms that determine the lifespan of mRNA molecules.
Protein Regulation: Various methods cells use to control protein activity, such as chemical modifications and localisation.
