2. What is a mutation?
• Over a lifetime our DNA can undergo changes
or ‘mutations’ in the sequence of bases, A, C,
G and T.
• This results in changes in the proteins that are
made. This can be a bad or a good thing.
• Mutations can occur during DNA replication if
errors are made and not corrected in time.
3. • Mutations can also occur as the result of
exposure to environmental factors such as
smoking, sunlight and radiation.
• Often cells can recognise any potentially
mutation-causing damage and repair it before
it becomes a fixed mutation.
• Mutations can also be inherited, particularly if
they have a positive effect.
What is a mutation?
4. • For example, the disorder sickle cell anaemia is caused by a
mutation in the gene that instructs the building of a protein
called haemoglobin. This causes the red blood cells to
become an abnormal, rigid, sickle shape. However, in African
populations, having this mutation also protects
against malaria.
• However, mutation can also disrupt normal gene
activity and cause diseases, like cancer
• Cancer is the most common human genetic disease;
it is caused by mutations occurring in a number of
growth-controlling genes. Sometimes faulty, cancer-
causing genes can exist from birth, increasing a
person’s chance of getting cancer.
What is a mutation?
5. Natural Selection
• Natural selection is one of the basic
mechanisms of evolution, along with
mutation, migration, and genetic drift.
• Darwin's grand idea of evolution by natural
selection is relatively simple but often
misunderstood. To find out how it works,
imagine a population of beetles:
6. • There is variation in traits.
For example, some beetles are green and
some are brown.
Natural Selection
7. Natural Selection
• There is differential reproduction.
Since the environment can't support unlimited population
growth, not all individuals get to reproduce to their full
potential. In this example, green beetles tend to get eaten by
birds and survive to reproduce less often than brown beetles
do.
8. Natural Selection
• There is heredity.
The surviving brown beetles have brown baby
beetles because this trait has a genetic basis.
9. • End result:
The more advantageous trait, brown coloration, which allows
the beetle to have more offspring, becomes more common in
the population. If this process continues, eventually, all
individuals in the population will be brown.
Natural Selection
10. Gene flow
• Gene flow — also called migration — is any movement of
individuals, and/or the genetic material they carry, from one
population to another. Gene flow includes lots of different kinds of
events, such as pollen being blown to a new destination or people
moving to new cities or countries. If gene versions are carried to a
population where those gene versions previously did not exist,
gene flow can be a very important source of genetic variation. In
the graphic below, the gene version for brown coloration moves
from one population to another.
11. What is genetic drift?
• Genetic drift is change in allele frequencies in
a population from generation to generation
that occurs due to chance events. To be more
exact, genetic drift is change due to "sampling
error" in selecting the alleles for the next
generation from the gene pool of the current
generation. Although genetic drift happens in
populations of all sizes, its effects tend to be
stronger in small populations.
