What is a mutation? Mutations are changes made to an organism’s genetic material. These changes may be due to errors in replication, errors during transcription, radiation, viruses and many other things. Mutations can occur within a specific gene (small scale), as well as to the chromosome as a whole (large scale).

Are mutations always bad? Favorable mutations present organisms with an advantage over others and ensure their survival. These mutations will accumulate in a population. Less favorable mutations are removed from the gene pool through natural selection. Organisms with these mutations will not survive.

A. Small Scale Mutations B. Large Scale Mutations

Small Scale Mutations: Gene Mutations There are three main types of small scale gene mutations. These all affect one nucleotide in a DNA triplet. (Point Mutations) Reversal/ Substitution (Lucky or unlucky) Deletions (Frame shift mutations) Insertions (Frame shift mutations)

Small Scale Point mutations occur when a single nucleotide in a gene is exchanged for another nucleotide. For example, an A could be exchanged for a T or a C could be exchanged for a G. These mutations have an effect on protein synthesis. One DNA triplet is altered, which can affect one or more codons and therefore one or more amino acids. Can be a reversal or substitution

Deletions Deletions are when one or more nucleotides are removed from the DNA sequence. As with insertions, this causes a shift in the reading sequence of DNA and can produce a completely different protein strand than the original. Deletions result in Frameshift Mutations

Insertions Insertions occur when one or more new nucleotides are inserted into the DNA sequence. When this occurs, there is a shift in the reading sequence of DNA during protein synthesis and a completely different protein strand may be formed. Frameshift

Video Animation hill.com/sites/ /student_view0/chapter11/a nimation_quiz_4.html hill.com/sites/ /student_view0/chapter11/a nimation_quiz_4.html Frame Shift Mutations

Large Scale Mutations: Affect large sections of a chromosome There are three major chromosomal mutations that can occur: Duplications Inversions Deletions

Duplication (LSM) Duplication occurs when a segment of a chromosome is doubled. The segment of DNA that is doubled may contain many genes. What affect would this have on the protein?

Inversions (LSM) Inversions occur when a piece of DNA is removed from the chromosome, inverted, and then placed back into the chromosome. When it is re-inserted, the genes are in reverse order. What affect would this have on the protein?

Deletions (LSM) Deletions occur when a whole chunk of the chromosome goes missing. Breaks in chromosomes can be caused by radiation, heat, viruses, chemicals, and other environmental causes. Consequences of these mutations will depend on what part of the chromosome has been deleted.

Deletions Examples of disorders caused by deletions: Prader-Willi Syndrome Deletion of the long arm on chromosome 15 Characterized by compulsive eating

Deletions Cri-du-chat syndrome Deletion of the short arm of chromosome 5