Welcome to THE CORE. Most of biology is connected via some very fundamental principles of how a typical cell works. These 4 pages condense and clearly explains these principles. Once you've read through THE CORE, you will find it much easier to follow all the pages in WHAT BIOLOGISTS DO and THE CONTEXT, as many biological topics in the media stem from these basic principles. You can also use this page as a launch pad to dip into other topics you might want to read about, look for speech bubbles and hyperlinks to other pages and educational media - and get in contact if you can't find one for a topic you'd like to read about!
DNA AND RNA
DNA is the information that makes you, you.
Your DNA is unique to you (unless you’re an identical twin) and every cell in your body has the same DNA. DNA is found in the nucleus (the round blob) of your cells. Your nerve cells and lung cells have the same DNA in their nuclei.
The CFTR channel is broken in people with Cystic Fibrosis, which is why people with this disease often get lung infections
…but if your nerve cells and lung cells have exactly the same DNA, how come they look so different?
Answer: cells look and behave differently depending on the type of proteins they have. Here's 3 examples of different cells:
messenger RNA or mRNA = an RNA transcript
Lung cells have channels such as the CFTR channel, which helps create mucus in your lungs so they remain healthy and infection-free. (See cystic fibrosis). Immune cells make lots of antibodies, proteins with a characteristic Y shape which stick to unwanted things in your body during infection. Pancreas cells make insulin to regulate your blood sugar levels. When insulin is not made properly you can get diabetes.
...so how do cells with the same DNA decide to make different proteins?
Answer: the central dogma of biology. DNA has the information to make every protein in all 200+ different cell types in your body. BUT that information is controlled so that only lung-appropriate proteins are made in lung cells, immune proteins in immune cells, and so on. This control happens in 2 different steps:
Step 1 – Transcription
Genes from the DNA are selected and copied. This process is called ‘transcription’ because the information is written out like a transcript. These transcripts are made of RNA. RNA is very similar to DNA except its single-stranded. They can move out of the nucleus, where the DNA is trapped, and into the rest of the cell.
Gene = enough DNA to make one transcript and one protein
Step 2 – Translation
Step 2 happens outside of the nucleus. The transcripts are read by protein machines, called ribosomes, in the cell that ‘translate’ the genetic information into the final product: the protein.
So in summary: DNA in the cell's nucleus has the information to make all different kinds of proteins. Since transcription and translation are tightly controlled processes, only specific proteins are made in specific cells at specific times.