12-4 MUTATIONS

I. KINDS OF MUTATIONS

1. Mutation- change in genetic material that can result from incorrect DNA replication

2. Point Mutations- gene mutations that result from changes in one or a few nucleotides

3. There are three types of point mutations:

a) substitutions,b) insertions, c) deletions.

4. Substitutions -usually affect only one amino acid.

5.Frameshift Mutations- a type of insertion or deletion

a)The addition or deletion of a nucleotide causes a shift in the grouping of codons

b)Can change every amino acid that follows the point of the mutation

c) can change a protein so much that it does not work normally

6. Insertion- an extra base is inserted into a base sequence

7. Deletion-the loss of a single base is deleted and the reading frame is shifted

DISCUSS W/ PARTNER:

•Use the following DNA sequence to show how it is changed by a point mutation and a frameshift mutation:

AAT CGA TCG

•Now write the mRNA sequence and the protein sequence produced by both of the “mutated” DNA sequences

DISCUSS W/ PARTNER:

•Which type of mutation (point or frameshift) is caused more damage and why.

ANSWER:

•Frameshift causes more damage because it changes all codons after the point of the mutation. The result is all of the amino acids will be changed which can affect the proper formation of a protein.

II. CHROMOSOMAL MUTATIONS

1. Deletions-the loss of all or part of a chromosome

2. Duplications -produce extra copies of parts of a chromosome

3. Inversions-reverse the direction of parts of chromosomes.

4. Translocations - part of one chromosome breaks off and attaches to another

III. SIGNIFICANCE OF MUTATIONS

1. Many mutations have little or no effect on gene expression

2. Some mutations are the cause of genetic disorders

3. Good mutations may produce proteins with new or altered activities that can be useful

5. Polyploidy -the condition in which an organism has extra sets of chromosomes

Polyploidy in plants results in plants that are larger & stronger than diploid plants.