Mutations These are errors made in the DNA sequence that are inherited. These may have negative side effects, no side effects or positive side effects.

Negative side-effects Some mutations may lead to a the development of a disease. Cystic fibrosis – mutation in the cystic fibrosis transmembrane regulator

Positive Mutations The human brain occurred through mutation. Caused a natural selection and the larger brains prevailed.

No effect The side effect may not surface immediately – especially eukaryotes We are diploid organisms meaning that we cancel the mutations out. If humans were haploid in nature much of the world population would be gone as we carry so many mutations.

Types of Mutations Silent mutations –No effect on the operation of the cell –Usually occurs in the introns of DNA –This means that post-transcription modification removes this mutation

Mutation can also be silenced through the redundant nature of the genetic code. Eg. Phenylalanine – UUU, UUC on mRNA Mistakes made during transcription or if a mutation is made and the third base is replaced with a G instead of an A – phenylalanine will still be created.

Missense mutation A mutation that results in the single substitution of one amino acid in the resulting polypeptide Change in the base sequence of DNA alters a codon – leading to a different amino acid in the sequence. Sickle cell anemia

Normal red blood cell Round flexible able to pass through tiny blood vessels.

Sickle cell Looses flexibility Is rigid and blocks blood vessesls depriving the area of blood supply

Nonsense mutations Mutation that converts a codon for an amino acid into a termination codon. During translation only part of the protein will be created and the fragment may be digested by proteases. Often lethal to the cell

Substitution and Deletion Missense and nonsense mutations occur because of substitutions or deletions of a base pair. Substitution – replacement of one base in a DNA sequence by another base Deletion – the elimination of a base pair or group of base pairs for a DNA sequence. Point mutations – if only one base pair.

By removing a base pair, it results in different base pairs being read. This will cause a drastic change in protein structure.

Insertion The placement of an extra nucleotide in a DNA sequence. Because DNA is read in triplets of nucleotides, and will cause different amino acids.

Frameshift Mutations Causes the reading frame of codons to change This results in different amino acids being incorporated into the polypeptide. Insertion and deletion can be considered Frameshift mutations, if they result in less than three codons being shifted. 3 nucleotides can be less serious.

Translocation The transfer of a fragment of DNA from one site in the genome to another location. A segment of a chromosome breaks and releases a fragment – this happens as the same thing is happening to another chromosome. The two fragments switch places – disrupting normal gene structure.

This new segment can be transcribed and translated. New protein with an altered function. Some leukemia are a result of this.

Transposable Elements Segments of DNA that are replicated as a unit from one location to another on chromosomal DNA They move from one location to another, making genes inactive. Various colours of Indian corn are a result of Transposable genes - McClintock

Could this happen???

Inversion Reversed its orientation in the chromosome No gain or loss of genetic material. Some genes may be disrupted.