What are mutations? changes to the base sequence of DNA
What can mutations be caused by? errors during DNA replication
What is a substitution mutation? one or more bases swapped for another
What is a deletion mutation? one or more bases are removed
What is an addition mutation? one or more bases are added
What is a duplication mutation? one or more bases are repeated
What is an inversion mutation? a sequence of bases is reversed
What is a translocation mutation? Sequence of bases is moved from one location in the
genome to another
Could be movement within same gene or to another
What could a mutation cause? change in the base sequence so a change in the amino
acid sequence so a change in the tertiary structure
Protein may not work e.g denatured enzyme
What else can a mutation cause? Can cause genetic disorders:
- inherited disorders caused by abnormal gene / cancers
Can increase likelihood of cancer
Can cause hereditary mutations:
- when gamete has a mutation for a genetic disorder or a type of cancer is fertilised
- mutation will be present in new fetus formed
Why might a mutation not have an effect? because the genetic code is degenerate
which mutations may not cause an effect? substitutions and inversions
which mutations will always cause an effect? additions duplications and deletions
why will these mutations always have an effect? all change the number if bases in the
DNA code
what effect is this? frame shift ; triplet code is read in a different way
what increases the rate of mutation? mutagenic agents
what are some examples of mutagenic agents? - UV radiation
- ionising radiation
- some chemicals
- some viruses
how do mutagenic agents increase the rate of mutations? Act as bases:
- chemicals called base analogs can substitute for a base during DNA replication
- thus changes base sequence
Alter bases:
- some chemicals can delete or alter bases
Changes structure of DNA:
- this causes problems during DNA replication
what are acquired mutations? mutations that occur in individual cells after fertilisation
what happens if these mutations occur in genes that control the rate of cell division?
cause uncontrolled cell division
what is result of a cell dividing uncontrollably? a tumour
what is a tumour? a mass of abnormal cells
what is the result of of tumours invading and destroying surrounding tissues? cancers
What are the two types of genes that control cell division? - tumour suppressor gene
- proto-oncogenes
What do mutations in these genes cause? cancer
What can happen to a tumour suppressor gene if a mutation occurs in the DNA base
sequence? tumour suppressor genes can be inactivated
,What do tumour suppressor genes do when functioning normally? slow cell division
How do tumour suppressor genes slow cell division? by producing proteins that stop
cells dividing or cause them to self- destruct ( apoptosis )
How do tumour suppressor genes operate if a mutation has occured then? The protein isn't
produced
The cells divide uncontrollably , rate of division increases resulting in a tumour
What happens to a proto-oncogene if a mutation occurs in the DNA base sequence?
effect of a proto-oncogene increases
What is a mutated proto-oncogene called? oncogene
What do proto-oncogenes do when functioning normally? stimulate cell division by
producing proteins that make cells divide
How do proto-oncogenes function when a mutation has occured? gene can become
overactive
stimulates cells to divide uncontrollably resulting in a tumour
What are the 2 types of cancer? malignant and benign
What are malignant tumours? - cancerous
- grow rapidly
- invade and destroy surrounding tissues
- spread to other parts of body via bloodstream / lymphatic system
- open wound
- blood leakage ( haemorrhage )
- dead tissue ( necrosis )
- uneven spread of cells
What are benign tumours? - not cancerous
- grow slower
- covered in fibrous tissues
- harmless
- can cause blockages / put pressure on organs
- some may become malignant
- even spread of cells ( homogeneous )
- intact surface
- membrane / capsule surrounds abnormal cells
How do tumour cells differ to different cells? - irregular shape
- nucleus larger and darker
- sometimes have more than one nucleus in cell
- don't produce all the proteins needed to function right
- different antigens on surface
- don't respond to growth regulating processes
- divide by mitosis more frequently
What is methylation? adding a methyl (-CH₃ ) group onto something
Why is methylation of DNA important? regulates gene expression:
- can control whether or not a gene is transcribed or translated
When does methylation become a problem? When it happens too much ( hypermethylation )
or too little ( hypomethylation )
What can abnormal methylation cause? growth of tumours in cancer related genes
Are tumour suppressor genes hypermethylated or hypomethylated? hypermethylated
What happens when tumour suppressor genes are hypermethylated? - genes are not
transcribed
- so the protein they produce to slow cell division arn't made
- so cells can divide uncontrollably by mitosis
, - tumours can develop
Are proto-oncogenes hypermethylated or hypomethylated? hypomethylated
What happens when proto-oncogenes are hypomethylated? - causes them to act as oncogenes
- this increases production of proteins
- encourages cell division
- stimulates cells to divide uncontrollably
- causes formation of tumours
What can an increased exposure to oestrogen over time lead to? thought to increase a
women's risk of breast cancer
how can oestrogen have an increased exposure? - starting menstruation earlier
- starting menopause later than usual
- taking oestrogen containing drugs like HRT
Describe 3 theories as to how oestrogen can contribute to the development of breast cancer.
1) - Oestrogen can stimulate certain breast cells to divide and replicate
- more cell divisions so more risk of mutation
- so increase risk of cells becoming cancerous
2) - ability to stimulate cell divisions means oestrogen can further assist cancerous cell into
rapidly dividing
- this helps tumours form quickly
3) - oestrogen can introduce mutations directly into DNA of certain breast cells
- increases chance of cells becoming cancerous
What are the 2 types of risk factors for cancer? genetic factors:
- some cancers linked with specific inherited alleles
- inherit allele more likely to get that type of cancer
environmental factors:
- exposure to radiation, lifestyle choices, like smoking, alcohol, and a high fat diet are all
linked to an increased chance
Why is data on variations very tricky to interpret? - some characteristics can be affected by
many different genes and many environmental factors
- difficult to know which factors are having the greatest effect
How can understanding the roles genes play in cancer lead to prevention? - if specific cancer
causing mutation is known then you can screen for it in a person's DNA
- knowing about increased risk means preventative steps can be taken to reduce it
e.g mastectomy or screened more often as early diagnosis increases chance of recovery
- more sensitive tests can be developed which can lead to earlier and more accurate diagnosis
How can understanding the role genes play in cancer lead to treatment and cure? - treatment
may be different for different mutations
- understanding can be useful for developing drugs to effectively target them
- understanding helps produce best treatment plan as some cancers more aggressive than
others
- gene therapy is replacing faulty genes for new ones ; need to know which genes cause
cancer to do this
What are stem cells? unspecialised cells that can develop into other types of cells
Where are stem cells found? embryo:
- where they become all the specialised cells needed to form a fetus
and in some adult tissues:
What can mutations be caused by? errors during DNA replication
What is a substitution mutation? one or more bases swapped for another
What is a deletion mutation? one or more bases are removed
What is an addition mutation? one or more bases are added
What is a duplication mutation? one or more bases are repeated
What is an inversion mutation? a sequence of bases is reversed
What is a translocation mutation? Sequence of bases is moved from one location in the
genome to another
Could be movement within same gene or to another
What could a mutation cause? change in the base sequence so a change in the amino
acid sequence so a change in the tertiary structure
Protein may not work e.g denatured enzyme
What else can a mutation cause? Can cause genetic disorders:
- inherited disorders caused by abnormal gene / cancers
Can increase likelihood of cancer
Can cause hereditary mutations:
- when gamete has a mutation for a genetic disorder or a type of cancer is fertilised
- mutation will be present in new fetus formed
Why might a mutation not have an effect? because the genetic code is degenerate
which mutations may not cause an effect? substitutions and inversions
which mutations will always cause an effect? additions duplications and deletions
why will these mutations always have an effect? all change the number if bases in the
DNA code
what effect is this? frame shift ; triplet code is read in a different way
what increases the rate of mutation? mutagenic agents
what are some examples of mutagenic agents? - UV radiation
- ionising radiation
- some chemicals
- some viruses
how do mutagenic agents increase the rate of mutations? Act as bases:
- chemicals called base analogs can substitute for a base during DNA replication
- thus changes base sequence
Alter bases:
- some chemicals can delete or alter bases
Changes structure of DNA:
- this causes problems during DNA replication
what are acquired mutations? mutations that occur in individual cells after fertilisation
what happens if these mutations occur in genes that control the rate of cell division?
cause uncontrolled cell division
what is result of a cell dividing uncontrollably? a tumour
what is a tumour? a mass of abnormal cells
what is the result of of tumours invading and destroying surrounding tissues? cancers
What are the two types of genes that control cell division? - tumour suppressor gene
- proto-oncogenes
What do mutations in these genes cause? cancer
What can happen to a tumour suppressor gene if a mutation occurs in the DNA base
sequence? tumour suppressor genes can be inactivated
,What do tumour suppressor genes do when functioning normally? slow cell division
How do tumour suppressor genes slow cell division? by producing proteins that stop
cells dividing or cause them to self- destruct ( apoptosis )
How do tumour suppressor genes operate if a mutation has occured then? The protein isn't
produced
The cells divide uncontrollably , rate of division increases resulting in a tumour
What happens to a proto-oncogene if a mutation occurs in the DNA base sequence?
effect of a proto-oncogene increases
What is a mutated proto-oncogene called? oncogene
What do proto-oncogenes do when functioning normally? stimulate cell division by
producing proteins that make cells divide
How do proto-oncogenes function when a mutation has occured? gene can become
overactive
stimulates cells to divide uncontrollably resulting in a tumour
What are the 2 types of cancer? malignant and benign
What are malignant tumours? - cancerous
- grow rapidly
- invade and destroy surrounding tissues
- spread to other parts of body via bloodstream / lymphatic system
- open wound
- blood leakage ( haemorrhage )
- dead tissue ( necrosis )
- uneven spread of cells
What are benign tumours? - not cancerous
- grow slower
- covered in fibrous tissues
- harmless
- can cause blockages / put pressure on organs
- some may become malignant
- even spread of cells ( homogeneous )
- intact surface
- membrane / capsule surrounds abnormal cells
How do tumour cells differ to different cells? - irregular shape
- nucleus larger and darker
- sometimes have more than one nucleus in cell
- don't produce all the proteins needed to function right
- different antigens on surface
- don't respond to growth regulating processes
- divide by mitosis more frequently
What is methylation? adding a methyl (-CH₃ ) group onto something
Why is methylation of DNA important? regulates gene expression:
- can control whether or not a gene is transcribed or translated
When does methylation become a problem? When it happens too much ( hypermethylation )
or too little ( hypomethylation )
What can abnormal methylation cause? growth of tumours in cancer related genes
Are tumour suppressor genes hypermethylated or hypomethylated? hypermethylated
What happens when tumour suppressor genes are hypermethylated? - genes are not
transcribed
- so the protein they produce to slow cell division arn't made
- so cells can divide uncontrollably by mitosis
, - tumours can develop
Are proto-oncogenes hypermethylated or hypomethylated? hypomethylated
What happens when proto-oncogenes are hypomethylated? - causes them to act as oncogenes
- this increases production of proteins
- encourages cell division
- stimulates cells to divide uncontrollably
- causes formation of tumours
What can an increased exposure to oestrogen over time lead to? thought to increase a
women's risk of breast cancer
how can oestrogen have an increased exposure? - starting menstruation earlier
- starting menopause later than usual
- taking oestrogen containing drugs like HRT
Describe 3 theories as to how oestrogen can contribute to the development of breast cancer.
1) - Oestrogen can stimulate certain breast cells to divide and replicate
- more cell divisions so more risk of mutation
- so increase risk of cells becoming cancerous
2) - ability to stimulate cell divisions means oestrogen can further assist cancerous cell into
rapidly dividing
- this helps tumours form quickly
3) - oestrogen can introduce mutations directly into DNA of certain breast cells
- increases chance of cells becoming cancerous
What are the 2 types of risk factors for cancer? genetic factors:
- some cancers linked with specific inherited alleles
- inherit allele more likely to get that type of cancer
environmental factors:
- exposure to radiation, lifestyle choices, like smoking, alcohol, and a high fat diet are all
linked to an increased chance
Why is data on variations very tricky to interpret? - some characteristics can be affected by
many different genes and many environmental factors
- difficult to know which factors are having the greatest effect
How can understanding the roles genes play in cancer lead to prevention? - if specific cancer
causing mutation is known then you can screen for it in a person's DNA
- knowing about increased risk means preventative steps can be taken to reduce it
e.g mastectomy or screened more often as early diagnosis increases chance of recovery
- more sensitive tests can be developed which can lead to earlier and more accurate diagnosis
How can understanding the role genes play in cancer lead to treatment and cure? - treatment
may be different for different mutations
- understanding can be useful for developing drugs to effectively target them
- understanding helps produce best treatment plan as some cancers more aggressive than
others
- gene therapy is replacing faulty genes for new ones ; need to know which genes cause
cancer to do this
What are stem cells? unspecialised cells that can develop into other types of cells
Where are stem cells found? embryo:
- where they become all the specialised cells needed to form a fetus
and in some adult tissues:
