Mutations

A mutation is a mistake in the cell’s DNA.

GTTACG GGTACG

DNA contains the information on how to make proteins.

Codons of the mRNA will code for a specific amino acid.

The order and length of the amino acid chain determine how it is folded and shaped.

If any of the amino acids are changed or the length is changed, the shape is different.

The protein’s function may change or not work at all.

Mutations are only passed on to your offspring if they occur in your gametes (egg or sperm)

Mutations that occur in your body cells may cause cancer.

Types of Mutations: Substitution

(point mutation: change in one nucleotide)

Examples Cystic fibrosis

Sickle Cell Disease GAG = glu GTG = val

One amino acid in the protein hemoglobin changes the shape of the cell

Silent Mutation:

Insertion This causes a frameshift mutation. All the

previous codons are now changed into different codons and therefore, different amino acids.

(also known as missense mutation)

Multiple insertions. A gene may be duplicated.

Deletion: A nitrogen base is deleted and a frameshift

mutation occurs.

A gene may be deleted.

Inversion The order of nitrogen bases can be

switched around. A few amino acids may change.

Genes may switch places. May not be expressed properly.

What causes mutations? Induced mutations: Toxic chemicals and

radiation

Examples of plants that were produced via mutation breeding are given in the table below.

Crop Cultivar Name Method Used to Induce Mutation

rice Calrose 76 gamma rays

wheatAbove sodium azide

Lewis thermal neutrons

oats Alamo-X X-rays

grapefruitRio Red thermal neutrons

Star Ruby thermal neutrons

burmuda grass

Tifeagle gamma rays

Tifgreen II gamma rays

Tift 94 gamma rays

Tifway II gamma rays

lettuceIce Cube ethyl methanesulphonate

Mini-Green ethyl methanesulphonate

common beanSeafarer X-rays

Seaway X-rays

lilac Prairie Petite thermal neutrons

St. Augustine grassTXSA 8202 gamma rays

TXSA 8212 gamma rays

Spontaneous mutations Mistakes in DNA replication.

Your DNA contains 3 billion base pairs. These are copied every time you make a new skin cell, liver cell, stomach cell….

Enzymes check the DNA to make sure there are no mistakes in the copying process.

But…. No process is 100% accurate. About one in every 50 million nucleotides

has a mutation occur. This means every new cell contains about

120 new mutations!

Worried? Don’t be… As much as 97% of your DNA doesn’t

code for proteins. We don’t know what this DNA is for. Also, Silent Mutations occur which don’t

change the protein.

Are all mutations bad? No, some are good.

Antibiotic resistance in bacteria

Sickle cell resistance to Malaria

Resistance to artherosclerosis

Immunity to HIV

Lactose tolerance

Blue Skin… (diaphorase deficiency)

Werewolf syndrome (congenital generalized hypertrichosis)