Mutations Genetic Changes

What is a mutation? A change in the base sequence of DNA

What causes mutations? Mistakes in replication (spontaneous) Mistakes in base pairs Environmental factors (mutagens) High energy radiation (X rays, UV rays) Chemicals (asbestos, cyanide, formaldehyde) High temperature

A mutagen Any agent that causes a change to the DNA sequence High energy mutagens (radiation) break the DNA strands apart causing deletions or substitutions Highly reactive mutagens (chemical) interact with the DNA usually causing substitutions

Mutations in reproductive cells Changes a sequence of nucleotides in a gene May produce a new trait for the offspring

Mutations in body cells Change in the nucleotide sequence only effects the individual and will not be passed down to the offspring i.e. Cancer, which effects genes that control cell division in mitosis

Types of Mutations Point mutations Frameshift mutations Chromosomal mutations Deletion Insertion Inversion Translocation

Point mutations A simple change in a single nucleotide base or “letter” of the gene sequence

Point mutations Original: The fat cat ate the wee rat. Point Mutation: The fat hat ate the wee rat (changing the r in cat to the h in hat). This change alters the meaning of the instructions significantly. In DNA, switching one base in the DNA sequence to a different base can change the protein that the gene makes.

Frame-shift mutations When one or more bases are added or deleted to the DNA strand. It shifts the reading of mRNA codons by one base

Frame-shift mutations Original:   The fat cat ate the wee rat. Frame Shift: The fat caa tet hew eer at. (the “t” from cat is removed) This type of mutation can make the DNA code meaningless and often results in a shortened protein. 

Frame-shift mutations

Deletions Occur when a part of the chromosome is left out. These can be small, such as the removal of just one "letter" or long enough to affect a large number of genes next to one another on the chromosome. Deletions can also cause frame-shift mutations.

Deletions Original: The fat cat ate the wee rat.                                                                                          Original:  The fat cat ate the wee rat. Deletion: The fat ate the wee rat. (deletion eliminated the word “cat.”)

Deletions                                                                                         

Insertions Result in the addition of extra DNA. Results is duplication of genes on the same chromosome. May also cause frame-shift mutations, and they generally result in a nonfunctional protein. 

Insertions Original: The fat cat ate the wee rat. Insertion: The fat cat xlw ate the wee rat.

Inversions An entire section of DNA is reversed. These can be small inversions within genes or large inversions that involve large regions of a chromosome and contain several genes.

Inversions Original: The fat cat ate the wee rat. Inversion: The fat eew eht eta tac rat.

Translocations Occur when a part of one chromosome breaks off and is added to a different chromosome

Translocations

Mutation Examples