IB Biology D1.2 Notes

HL students need to know more details about transcription and translation. Within the concept of gene expression, it is important to understand that the DNA sequences that are transcribed do not only result in proteins. There are several types of DNA sequences:

1. Coding DNA - DNA that codes for proteins.
2. Non-coding DNA - DNA that does not code for proteins. There are several types:
   1. Regulators - these promote or repress transcription of adjacent coding sequences.
   2. Introns - these are used during mRNA processing to aid the splicing of exons.
   3. Telomeres - the lagging strand loses a little bit of DNA every time it undergoes replication. Telomeres are extra lengths of DNA that prevent the loss of vital DNA.
   4. tRNA and rRNA production - these sequences are transcribed to form tRNA for translation and rRNA (ribosomal RNA) to form ribosomes.

In this topic, you will learn about about several of these non-coding sequences.