BIOLOGY 12 Mutations

Control Mechanisms approximately 35 000 genes in a human most proteins are not needed all the time

Control Mechanisms gene regulation – the turning on or off of specific genes depending on the requirements of an organism transcription factors – turn on the genes when required How Genes are Regulated http://www.youtube.com/watch?v=MkUgkDLp2iE

Control Mechanisms “Housekeeping genes are those genes that are always expressed because they code for proteins that are constantly required by the cell, hence, they are essential to a cell and always present under any conditions. The proteins they code are generally involved in the basic functions necessary for the sustenance or maintenance of the cell. Examples of housekeeping genes include actin (for muscle contraction) and GAPDH (breaks down glucose during glycolysis).” Biology-Online.org

Control Mechanisms housekeeping genes – genes that are switched on at all times because they are needed for life functions vital to an organism List of housekeeping genes for humans http://en.wikipedia.org/wiki/Housekeeping_gene#Transcription_Factors

Control Mechanisms 4 levels of control transcriptional – regulates which genes on DNA are transcribed posttranscriptional – mRNA undergoes changes before being translated translational – regulates how often and how fast mRNA is translated to a protein posttranslational – protein is told when to become active and for how long

Mutations changes in the DNA sequence errors that occur during DNA replication or repair, which then get transferred to mRNA and then to the protein

Mutations causes include: spontaneous error mutagens polymerase III reads it wrong and exonuclease misses it mutagens chemicals high energy radiation (x rays and uv rays)

Mutations when would a mutation be passed on to the next generation? from sperm and egg cells during reproduction

Types of Mutations substitutions insertions deletions silent missense nonsense insertions deletions

Mutations: Substitutions the replacement of one base by another base A C G G T T A C A A becomes: A C G G T C A C A A

Mutations: Substitutions silent mutation no change in the amino acid it codes for therefore does not cause any phenotypic change (observable characteristics) no effect on operation of the cell ACA and ACU both code for Threonine so mutation from A to U would not cause a problem

Mutations: Substitutions missense mutation codes for a change in one amino acid in the polypeptide AUG AAC CCC ACA UAA Met – Asn – Pro – Thr – Stop AUG AAC CCC CCA UAA Met – Asn – Pro – Pro – Stop

Mutations: Substitutions

Mutations: Substitutions nonsense mutation codes for a change from one amino acid to a STOP codon AUG CCC AAC ACA UAA Met – Pro – Asn – Thr – Stop AUG CAC UAA ACA UAA Met – Pro – Stop

Mutations: Insertions the placement of an extra nucleotide TAC CCG CAA GTA TAT CCC GCA AGT A

Mutations: Insertions

Mutations: Deletions deletions the elimination of a base pair or group of base pairs

Mutations: Point and Frame Shift point mutations – specific to one base pair often substitutions frame shift mutations – change the reading frame, causing many problems often insertions or deletions

Mutations: Point and Frame Shift original: the fat cat ate the wee rat point mutation: the fat hat ate the wee rat frame shift: the fat caa tet hew eer at

Mutations name each type of mutation: Substitution Insertion Frame Shift Deletion