1. BIOLOGY 12
Mutations

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

3. 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

4. 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

5. 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

6. 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

7. 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

9. 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)

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

11. Types of Mutations substitutions insertions deletions silent missense
nonsense
insertions
deletions

12. 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

13. 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

14. 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

15. Mutations: Substitutions

16. 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

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

18. Mutations: Insertions

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

20. 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

21. 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

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