Download Gene Mutations and Cancer Part 2

1 of 9
© Boardworks Ltd 2016
DNA methylation
The expression of tumour suppressor genes and protooncogenes can be affected by DNA methylation.
In this process, a methyl group (CH3)
is added to DNA. This prevents the
enzymes involved in transcription
from binding to the DNA.
This switches off, or inhibits,
the expression of specific genes.
If a gene is de-methylated,
it is switched on.
This is an example of an
epigenetic change.
2 of 9
© Boardworks Ltd 2016
Hyper-methylation
DNA methylation is a normal cell process that affects different
genes throughout a person’s life.
However, some environmental factors, such as smoking,
increase the risk of abnormal DNA methylation patterns.
Tumour suppressor genes
are usually switched on to
slow down cell division.
If parts of a tumour
suppressor gene become
heavily methylated, the gene
is de-activated, and it no
longer inhibits cell division.
3 of 9
tumour suppressor gene:
switched on
methylation
switched off
© Boardworks Ltd 2016
Hypo-methylation
The expression of proto-oncogenes is usually suppressed
by DNA methylation.
proto-oncogene:
If a proto-oncogene is
de-methylated, the gene is
permanently activated, and
cell division is stimulated.
switched off
de-methylation
An increase in the expression
of proto-oncogenes or a
decrease in the expression of
tumour suppressor genes can
cause cancer.
4 of 9
switched on
Proto-oncogene changes
to oncogene.
© Boardworks Ltd 2016
Oestrogen and breast cancer
Certain breast cancers grow in response to oestrogen,
which is a sex hormone.
The cancer cells have oestrogen
receptors.
When oestrogen binds to these
receptors, they send a signal to
the cell to stimulate cell division.
The higher the body’s
oestrogen concentration, the
more the cancer cells will grow.
This type of breast cancer can be treated by hormone
therapy, where the body’s oestrogen production is suppressed.
5 of 9
© Boardworks Ltd 2016
Genetic risk factors
Mutations in the genes BRCA1 and BRCA2 are thought to
be associated with breast cancer.
The graph shows the incidence of women developing breast
cancer below the age of 70 years. What does the data show?
BRCA1 and BRCA2
are tumour suppressor
genes that produce
proteins that help to
repair damaged DNA.
How might this
explain the
increased risk?
6 of 9
© Boardworks Ltd 2016
Environmental risk factors
This data shows the relationship between breast cancer
incidence, age, and alcohol consumption in women.
6 units of alcohol per day
What does the data
show?
3 units of alcohol per day
no alcohol
Is this direct evidence
that alcohol causes
breast cancer?
What environmental
factors other than
alcohol might affect
breast cancer risk?
7 of 9
© Boardworks Ltd 2016
Multiple-choice quiz
8 of 9
© Boardworks Ltd 2016
Want to see more?
This is only a sample of one of thousands of
Boardworks Science presentations.
To see more of what Boardworks can offer, order a
full presentation completely free:
www.boardworks.co.uk/sciencepresentation
9 of 9
© Boardworks Ltd 2016