Genes and mutations

What are genes? A molecular unit of heredity The name for stretches of DNA and RNA that code for a specific protein (which has a specific function in the organism)

Genes: Coding regions Your DNA has coding and non-coding regions Genes are the proteins that are made from the coding regions.

Genes: Inheritance Every person has two copies of each gene – one inherited from each parent Most genes are the same in all humans – only a small number are different (less than 1%)

Genes: mutations Genes can be mutated when the DNA is mutated There are two types of DNA mutations: Point Mutations: a change in a single base pair Result: changing a single nitrogen base can change the entire structure of a protein (due to change in one amino acid) Frameshift Mutation: single base is added or deleted from DNA Result: every amino acid after shift is changed

Genes: Mutations Example of a Point Mutation: THEDOGBITTHECAT THE DOGBITTHECAR …changing a single letter changes the meaning

Genes: Mutations Example of a Frameshift Mutation (deletion): THEDOGBITTHECAT THE DOBITTHECAT …deleting a single letter changes the reading of everything down the line from the mutation.

Chromosomal mutations Deletions: part of chromosome is left out

Chromosomal mutations Insertions: duplication of genes in the same chromosome

Chromosomal mutations Inversions: part breaks out and reinserts itself backwards

Chromosomal mutations Translocations: part breaks off and is added into a different chromosome

Chromosomal mutations Non-Disjunction: failure of homologous chromosomes to separate properly during meiosis

What causes mutations? Random events Environmental agents (X-rays, UV light, radioactivity, etc.)

Results of mutations If it occurs in gametes (sex) cells: Can cause birth defects, abortion, or no change Few are passed on to next generation because zygote usually dies If it occurs in somatic (body) cells: Can lead to cancer, or no change