Gene Expression
Higher Tier Only
- The human genome contains all of the genetic information that an organism requires to function
- This includes sections of DNA which are called coding DNA and non-coding DNA
- Coding and non-coding DNA both play a role in gene expression
Coding DNA
- Coding DNA refers to the genes of an organism which provide the instructions required to synthesize proteins
- Only a small proportion of the genes in the genome may be expressed at any time
- This is because genes must be activated if they are to be expressed
Non-coding DNA
- Non-coding DNA does not code for proteins
- However, it can influence protein synthesis through interactions with the coding regions of DNA
- Non-coding DNA can cause activation or deactivation of genes in the coding DNA
DNA is made up of regions of coding DNA and regions of non-coding DNA, both regions are involved in gene expression
Mutations and gene expression
- Some genetic variants (resulting from mutation) can influence the phenotype of the organism
- Variants which directly impact gene expression work by
- Altering the DNA base sequence within the coding DNA regions of the genome
- The mutation significantly alters the structure of the protein produced
- This results in a non-functional protein
- For example, an enzyme active site may be altered significantly so that the substrate no longer fits
- Variants which indirectly impact gene expression work by
- Altering the DNA base sequence within the non-coding DNA regions of the genome
- This mutation can have two effects on the coding DNA
- It may activate genes in the coding regions resulting in transcription of a gene which was previously not being expressed
- A protein is produced
- It may inactivate genes in the coding regions which halts transcription of a gene which was previously being expressed
- A protein isn't produced
- It may activate genes in the coding regions resulting in transcription of a gene which was previously not being expressed
Gene expression can be affected directly and indirectly by mutations within the coding and non-coding DNA
