Gene Mutations and Expression

Mutations -mutation- random change in genetic material -can happen during replication, transcription, translation, or cell division

Point Mutations -Point mutation – a single base pair is affected -It could be a deletion, insertion, or substitution. Substitution

Insertion Extra base pair is added (causes a frameshift)

Deletion Base pair is removed (causes frameshift)

Duplications -duplication- part of the DNA is duplicated

Inversions -inversion - part of the DNA is reversed A-T-C-G-T-T-G-C A-T-C-G-T-C-G-T

Translocations -part of the DNA is moved to a different spot A-A-A-T-C-G-T-A-C T-C-G-A-A-A-T-A-C

Mutation Outcomes Missense – the wrong amino acid is added

Mutation Outcomes Nonsense – a stop codon is produced early causing the amino acid chain to end early.

Mutation Outcomes Silent – although the wrong codon is produced but the correct amino acid is sill added (thus no change) Wobble – more than one codon can code for the same amino acid. (makes silent mutations possible)

Prokaryotic Gene Regulation Operator – a control site within the promoter that can be blocked to stop transcription (turns the gene off) Repressor – a protein that slides into the operator to block transcription (the RNA polymerase cannot attach and pass) Operon – promoter + operator + genes they control

Co-repressor Co-repressor – a molecule that combines with the repressor to change the repressor into its active form. (thus turning the gene off) Ex. E. Coli in our colon only make the amino acid Tryptophan if we are not providing it for them.

Negative regulation Negative regulation – gene is off until turned on Repressor is naturally active Ex. If no lactose (from milk) is present in the colon E. Coli does not produce enzymes to break down milk

Inducer (negative) Inducer – molecule that bonds with the repressor to make it inactive (turns the gene on) If milk is present E. Coli turns on genes to produce enzymes to break down the milk.

Positive Gene Control Positive regulation – even though the repressor is inactive and the gene is on, protein production must be stimulated. Ex. If lactose and glucose are both present E. Coli chooses to use glucose and does not produce enzyme to break down lactose (even though the lactose operon is on) Activator

Activator (positive) Activator – stimulates the production of a protein in a gene that is on (calls for RNA polymerase to attach) If glucose is in short supply and lactose is available, E. Coli. will produce enzymes to breakdown lactose. Activator

Eukaryotic Regulation Enhancers – sites that call for specific activators to stimulate the production of certain proteins.

Histone Acetylation Histone Acetylation – acetyl groups are added to histone tails (neutralizes their charges) Histones spread exposing DNA so transcription can be initiated.

DNA Methylation DNA methylation – a methy group is added to a base. (usually found in inactive genes)

Proteasomes Proteasomes - degrade old protein Ubiquitin – molecules added to proteins needed to be broken down.

Micro and Small Interfering RNA Micro RNA (miRNA) – single stranded degrades or blocks translation of mRNA. Small Interfering RNA (siRNA) - double stranded but functions similarly to siRNA (may help fight viruses)