Unit 7 - Point/Gene Mutations & Electrophoresis - H Bio

Point mutation

a change to the DNA or mRNA that affects the specific amino acid sequence resulting in an incorrectly assembled protein

Point mutations give rise to the development of

ex.

• diabetes

• sickle cell anemia

Types of point mutations

• addition

• deletion

*which could both lead to non-functioning proteins (→ non-existent)

• substitution

Addition

adding a base to the DNA or mRNA sequence

Deletion

removing a base from the DNA or mRNA sequence

Both addition and deletion

cause frameshift mutations!

ex. addition frameshift

• normal mRNA to mutated mRNA

Substitution

replacing one base with another in a DNA or mRNA sequence

• does not cause a frameshift

Missense Mutation

amino acid changed to a different amino acid

• (can be good, okay, or very bad)

Nonsense Mutation

amino acid changed to a “stop”

• protein will not function (non-existent)

Silent Mutation

codes for same amino acid

• (doesn’t matter)

Electrophoresis

technique using an agarose gel and electric current to distinguish differences between individual’s DNA or differences between normal and abnormal proteins based on their size and charge

Comparing DNA

fragmented by restriction enzymes, cut DNA at specific base sequences

Different individuals will have

different number/sizes of fragments

Fragments of different sizes/mass move at

different rates from (-) pole of an electric field toward (+) pole

Fragments that have migrated are

stained to indicate their position after a period of time

RFLP

Restriction Fragment Length Polymorphism (Genetic Fingerprint)

• unique banding pattern of an individual’s DNA after being treated by several restriction enzymes

Proteins have overall (-) charge as a result of

the amino acids they contain

• overall charge is different for different proteins

When comparing a “normal” protein to a “mutated” protein,

they will have slightly different overall charges due to differences in amino acid sequences

Comparing the amount of migration of a “normal” protein to that of a “mutated” protein on an electrophoresis gel

enables differentiation between the two forms of the protein