Mutations

What are Mutations?

Now and then cells make mistakes in copying

their own DNA, inserting the wrong base or

even skipping a base as a strand is put

together.

These variations are called mutations.

Mutations = Changes in the DNA base sequence

There are two main types of mutations:

1) Chromosomal Mutations: Involve the

change in number or structure of

chromosomes. These mutations can change

the location of genes on chromosomes and

can even change the number of copies of

some genes. (studied last unit)

2) Gene Mutations: Involve changes to the

individual nucleotides in the DNA

Gene Mutations

Point Mutations: mutation that involves changes in

one or a few nucleotides. This type of mutation includes

substitutions, insertions, and deletions.

1) Substitutions: one base is changed to a

different base

2) Insertions: one base is added

3) Deletions: one base is deleted

Fra

me

sh

ift m

uta

tions

THE DOG BIT THE CAT

THE DOG BIT THE KAT

OR THE DOG BIT THE CAR

THE DDO GBI TTH ECA THE OGB ITT HEC ATS

THE DOG BIT THE KAT

OR THE DOG BIT THE CAR

THE DDO GBI TTH ECA THE OGB ITT HEC ATS

Effect: Depends on how drastically it changes the shape of the protein, or if the change is in a critical location

Original Protein

Mutated Protein

THE DOG BIT THE KAT

OR THE DOG BIT THE CAR

THE DDO GBI TTH ECA THE OGB ITT HEC ATS

Effect: Depends on how drastically it changes the shape of the protein, or if the change is in a critical location

Effect: These two cause MAJOR changes in the amino acid sequence, since sequence is still read in groups of three.

Harmful or Helpful?

Mutations may have no effect (silent mutation)

a bad effect

a good effect

Sickle Cell Anemia Sickle Cell Anemia- point mutation, this mutation causes

the hemoglobin in red blood cells to distort to a sickle

shape when deoxygenated. The sickle cells clog in the

capillaries, cutting off circulation. Having two copies of the

mutated gene causes sickle cell anemia, but having one

copy does not can actually protect against malaria!

Example Two: CCR5 protein

CCR5 is a membrane protein that exists on

the surface of human white blood cells.

HIV uses the CCR5 protein as a chemical

doorway to infect (enter) white blood cells.

white

blood cell

with CCR5

mutation

mutated CCR5

HIV cannot enter

mutated cells! normal

white blood

cell

normal CCR5

HIV

Are Mutations Inherited?

When mutations occur in body cells (skin,

lung, brain, etc), they can’t be passed on to

offspring.

When mutations occur

in sex cells, they can be

passed on to offspring.