What do genes actually do?1

Genes are inherited instruction codes for making proteins. Proteins have a huge range of jobs, including structural support, recognizing infections, breaking down food and helping to generate energy. Each of us has around 22,000 genes!

Genes are made up of DNA, which stands for deoxyribose nucleic acid. DNA exists as a coiled spiral known as a double helix. This is then organized into x-shaped chromosomes (see figure 1).

We all have 46 chromosomes – 23 pairs – with one of each pair given to us by each of our parents when we’re conceived. One pair is the sex chromosomes: females have two X chromosomes, and males have an X and a Y chromosome.

How we inherit genes1

We all have two of each gene (with a few exceptions – but that’s another story) inherited from each parent. These are called alleles. The features that we end up with are influenced by the alleles we receive. Further, the feature might only appear if we have two identical copies of the allele: these are known as recessive. If a feature needs only one allele, it is called dominant.

Patterns of inheritance and sex chromosomes1

There are different inheritance patterns.

  • The autosomal recessive pattern is when conditions require two abnormal alleles which are not linked to the sex chromosomes. Someone with only one copy of the faulty gene is know as a carrier. If 2 parents are both carriers of the faulty gene, each of their children could either have no condition and not be a carrier, or have no condition and be a carrier or have the condition because they receive the 2 copies of the faulty gene (see figure 2).
  • The autosomal dominant pattern is when only one copy of a faulty gene not linked to the sex chromosome is involved.
  • The X-linked recessive pattern is when the faulty gene is located on the X chromosome. As males only have one copy of the X chromosome, they are more likely to develop X-linked recessive illnesses (such as hemophilia) than females.

The gene affected by Gaucher disease2

Gaucher disease is caused by a fault in a single gene called GBA and has an autosomal recessive inheritance pattern (see figure 2). This means that the Gaucher patient has two faulty versions of the allele, coming from their 2 parents.

References

1. Anatomy and Physiology. OpenStax at Rice University. Published 25 April 2013. ISBN-13: 978-1-947172-04-3. Available at https://openstax. org/details/anatomy-and-physiology. Accessed September 2019

2. GBA gene. NIH. Available at https://ghr.nlm.nih.gov/gene/GBA. Accessed September 2019