Understanding the genetics

Protein

The molecules in the body that ‘do’ things. They are chains of amino acids. The “cake” created by following the “recipe” (gene).

Mutation

An alteration in the gene that means the protein is now made differently to how it should be.

Substitution

When a letter in the DNA has been changed to a different one

E.g. “sugar” being spelt “Spgar”

Nonsense mutation

When a substitution of a letter in the DNA means that the protein terminates early making it incomplete. Depending on where the mutation happens, it could make it very short, or it could be almost complete:

“Add the sugar then 50 grams of flour” becomes “Add the sugar then 50.“

Mosaicism

When not all the cells in the body have the mutation.

DNA

A double stranded string of letters (bases) (AGCT) that bundle together to form chromosomes. The order of the letters is very important. (See diagram at bottom of page).

Deletion

A type of mutation: When a letter (or letters) is missing from the DNA

E.g. the ‘a’ from “sugar”

Duplication

When a section of DNA has been replicated:

“Add the sugar then 50 grams of Add the sugar then 50 grams of Add the sugar…”

Frameshift mutation

When an extra letter added or deleted on the DNA means the whole ‘instruction book’ downstream of the change now makes no sense, because all the letters get shifted one place, either up or down:

“Add the sugar then 50 grams of flour” becomes “Add ths ugart hen5 0 gramso fflour“

Gene

A section of DNA that holds the ‘recipe’ to make a protein.

“Add the sugar then 50 grams of flour…”

The protein would be a cake, for example. The gene would be the recipe for the cake.

Addition

A type of mutation: When an extra letter (or letters) has been added

E.g. two ‘a’s’ in “sugar”

Missense mutation

When a substitution of a letter in the DNA just makes a tiny change to the protein:

“Add the sugar then 50 grams of flour” becomes “Add the suger then 50 grams of flour.”

Chromosome

Bundled up DNA  containing many genes. Each human cell contains 46 chromosomes. These come in pairs. However, the sex chromosomes are different in males and females. Females have a pair of X chromosomes. Males have an X and a Y chromosome. They contain different genes, hence having different names. The CASK gene is found on the X chromosome. So males only have one copy of the gene, whilst females have two copies.