Chapter 12 Section 4 Mutations. Mutations DNA contains the code of instructions for cells....

Chapter 12 Section 4 Mutations

Mutations

• DNA contains the code of instructions for cells.

• Sometimes, an error occurs when the code is copied. - Such errors are called mutations.

• Mutations are changes in the genetic material.

2 Types of Mutation

• 2 types:

1. Gene mutation produce changes in a single gene

2. Chromosomal mutation produce changes in whole chromosomes

Gene Mutations• Point mutation gene mutations involving

changes in 1 or a few nucleotides

- Occurs at a single point in the DNA sequence

• Includes:

a. Substitutions 1 base changed to another

b. Insertions a base is inserted or added

c. Deletions a base is deleted or removed

Cont. Gene Mutations

Substitution InsertionDeletion

• Substitutions usually affect no more than a single amino acid

• The effects of insertions/ deletions can be much more dramatic.

Cont. Gene Mutations• Frameshift mutations a

change that shifts the “reading frame” of the genetic message (caused insertion/ deletion)

- By shifting the reading frame, frameshift mutations may change every amino acid that follows the point of mutation.

- Can alter a protein so much that it is unable to perform its normal function

Gene MutationPicture of “Mighty Belgium Blue” cattle

- Alter in myostatin gene

- Produces meatier cattle/ 20% more meat per animal on roughly the same food intake as ordinary animals

Chromosomal Mutations• Changes in the number or structure of chromosomes

a. Deletions involves loss of all or part of a chromosome

b. Duplication produce extra copies of parts of a chromosome

c. Inversions reverse the direction of parts of a chromosome

d. Translocation when part of a chromosome breaks off & attaches to another

Significance of Mutationsa) Harmful mutations

- Produce defective proteins that disrupt normal biological activities- Causes genetic disorders- Associated with many cancers

b) Beneficial mutations- Produce proteins w/ new/ altered activities that can be useful to organisms in different/ changing env- Source of genetic variability in species- Polyploidy an organism w/ extra sets of chromosomes

Ex: polyploid plants are often larger & stronger then diploid plants (bananas & many citrus

fruits)

Polyploid