1. M15 Change in the base sequence of DNA can lead to the alteration or absence of proteins and to the appearance of new characteristics in the descendants
M15.1 Know that changes in the DNA sequence are called ‘mutations’.
The differences between species is due to an accumulations of DNA mutations
This process seems to have occurred over millions of years

2. M15 cont- Mutations are permanent changes
This permanency means ultimately the source of new genes
In nature, mutations are random events, and can be triggered or increased by different things
The majority of mutations are HARMFUL
Some do provide a chance for variability though, meaning nature can select something which may enhance the survival of a species-natural selection covered in O11.1

3. Mutations are categorised as follows:
BASE SUBSTITUTIONS: One nucleotide substituted for another- a wrong base put into position on the DNA

4. MUTATIONS CONT: BASE INSERTIONS OR DELETIONS:
This involves either adding or deleting a nucleotide and has disastrous effects in most cases
M RNA is read in 3 bases, the codon…which codes for the amino acid, these join….chain…folds…protein…
Structure=function
If a base is added or deleted, nucleotide can’t be read correctly, structure changes and therefore function….could be malfunction in a disastrous way.
See page 38 text

5. Bigger Mutations
These occur if there are changes to the chromosome and include:
Translocations-one part of the chromosome is moved to another
Inversions=a segment in a chromosome may be flipped upside down
Duplications-parts of a chromosome appear twice

6.   M15.2 Know that the mutations rate can be increased by radiation, mutagenic chemicals and heat.
Mutations occur in germ line cells-those that produce gametes, this means they can be passed on to the next generation if the mutation is not fatal to the cell
Mutations that occur during replication or recombination-spontaneous mutations
Mutagens are things which increase the rate of mutations and can be physical or chemical
Physical:
High energy radiation-x=rays/ultra violet light

7. M15.2 cont:
Chemical: these can have an effect as they often mimic the normal DNA bases
All mutations can lead to changes in the genes that control cell division and therefore lead to the development of cancer.

8. M15.3 Explain how inheritable mutations can lead to change in the characteristics of the descendants
If mutations represent changes in DNA
AND DNA controls all the functions of a cell…
Then if these are inherited..the functions. or structure of an organism can be altered
If they are helpful mutations it can lead as we said to genetic and species variability…or can be harmful in terms of genetic diseases or conditions

9. M15.3 cont
One nucleotide mutations- cystic fibrosis and sickle cell anaemia
Read and note if you need more info from page 39
Haemophilia-genetic disorder where those afflicted bleed excessively-page 41/42