MUTATIONSMUTATIONSMistakes in DNAMistakes in DNA

The Big Picture Chromosome

Supercoils

Coils

Proteins

DNA

double

helix

•Chromosomes are made up of super coiled strands of DNA

•Genes are

•sections of your chromosome

•made up of DNA

Mutations Mutations • Mutations are changes in genetic

material.

• There are two major mistakes that can happen:

1. Chromosomal Mutations

2. Gene Mutations

Type 1:Type 1: Chromosomal Mutations Chromosomal Mutations

• Whole chromosome is affected.• Large sections of DNA can be

– Removed from a chromosome– Added to a chromosome– Rearranged within a chromosome– Switched with DNA from another chromosome.

• These mutations are usually very

harmful

Chromosomal MutationsChromosomal MutationsDeletion loss of material

Duplication addition of material

Inversion rearrangement of material

Translocation switching material with another chromosome

Type 2: Gene MutationsType 2: Gene Mutations

• Changes that occur in a single gene. • Change occurs at the DNA nucleotide

levelHydrogen bonds

Nucleotide

Sugar-phosphate backbone Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Two Types of Gene MutationsTwo Types of Gene Mutations

1. Point mutations: one nucleotide that affects one amino acid.

Example: Substitution

C changes to G

Two Types of Gene MutationsTwo Types of Gene Mutations

2. Frameshift mutations: • involve the reading of the DNA or m-RNA

strand• many amino acids are affected.

Examples: Insertion Deletion

Mutation Can Be…Mutation Can Be…1. Neutral (a.k.a. Silent)

• Example: Substitution

• UCU = Serine if the last U is changed to C, A or G the mRNA will still make Serine

2. Harmful

• Example: Substitution

• Sickle Cell Anemia

• There is a change 17th nucleotide in the code for hemoglobin

• A is changed to a T - GAG changes to GTG

• How does this change the amino acid?

• GLU changes to VAL

• This changes hemoglobin’s shape from round to sickle shaped

Mutation Can Be…Mutation Can Be…

3. Harmful (more harmful)

• Example: Frameshift - Deletion

• Shifts the whole reading frame

• Changes the amino acids produced

4. Harmful (even more harmful!)

• Example: Chronic myelogenous leukemia

• Translocation

• Pieces of 2 chromosomes switch

• Causes white blood cells to

divide and reproduce improperly.