Control Of Gene Expression Flashcards
What is a mutation?
Any change to the base sequence of DNA in an individual gene or in the structure of a chromosome
What is a substitution mutation?
One or more bases are swapped for another e.g. ATGCCT becomes ATTCCT
- point mutation
- results in either the same base (degenerate), a single different base (missense) or if new base codes for a stop codon the rest of the polypeptide will not from (truncated)
What is a deletion mutation?
One or more bases are removed e.g. ATGCCT becomes ATCCT
- frame shift mutation
What is an addition mutation?
One or more bases are added e.g. ATGCCT becomes
- frame shift
What is a duplication mutation?
One or more bases are repeated e.g. ATGCCT becomes ATCCCCCT
- a number of bases are repeated causing frame shift
What is an inversion mutation?
A sequence of bases is reversed e.g. ATGCCT becomes ACCGTT
What is a translocation mutation?
A sequence of bases is moved from from location in the genome to another, for example movement within the same chromosome or movement to a different chromosome
What is a whole chromosome mutation?
An entire chromosome is lost or replaced during cell division
- e.g. Down syndrome caused by extra 21 chromosome
What are the effects of mutations?
- production of new advantageous protein = reproductive advantage
- neutral mutation = no change
- production of a disadvantageous protein = fatal and/or disease causing
How do mutagenic agents increase the rate of mutation?
Mutagenic agent examples = UV radiation, ionising radiation, chemicals and some viruses.
- act as a base = base analogs can substitute for a base during DNA replication, changing the base sequence in the new DNA
- altering bases = some chemicals can delete or alter bases e.g. alkylating agents can add an alkyl group to guanine changing its structure to pair with thymine
- changing the structure of DNA = radiation can cause the DNA structure to change causing problems in DNA replication
How can mutations cause cancer?
If mutations occur in the genes that control the rate of cel division, it can cause uncontrolled cell division.
- this can result in a tumour, tumours that invade and destroy surrounding tissue are called cancers.
How do mutations in tumour suppressor genes cause cancer?
When normal they slow cell division by producing proteins that stop cells diving or causing them to self-destruct (apoptosis)
- the genes can be inactivated by mutation and the cells divide uncontrollably.
- both copies of the gene need to be mutated to cause cancer
How can mutations in proto-oncogenes cause cancer?
When normal they stimulate cell division by producing proteins that makes cells divide.
- if a mutation occurs the gene can become overactive and that stimulates uncontrolled cell division
- mutated proto-oncogene is called an oncogene
What is the difference between malignant and benign tumours?
Malignant = cancerous, rapidly grow and invade and destroy surrounding tissue, cells can spread to other parts of the of the body in the bloodstream or lymphatic system.
Benign = not cancerous, grow slower, often covered in fibrous tissue, harmless but can cause blockages and put pressure on organs.
How do tumour cells look and function differently to normal cells?
- irregular shape
- nucleus is large and darker
- different antigens on their surface
- don’t respond to growth regulating processes
- divide by mitosis more frequently then normal cells
How can abnormal methylation of cancer-related genes cause tumour growth?
- adding a methyl (-CH3) group
- when it is hypermethylated or hypomethylated
- when tumour suppressor genes are hypermethlyated the genes are not transcribed - so the proteins aren’t made
- when proto-oncogenes are hypomethlyated = act as oncogenes - increasing production of proteins
How can increased oestrogen contribute to some breast cancers?
- oestrogen can stimulate certain breast cells to divide and replicate, more cells divisions increases the change of mutations occurring and so increase the chance of them becoming cancerous
- this ability to stimulate cell division could also mean that is cells do become cancerous, their rapid replication could be further assisted by oestrogen
How can cancer be prevented?
How can cancer be treated or cured?
What does totipotent mean?
What does multipotent mean?
