Mutations and Gene Expression Flashcards
Types of mutations:
Substitution Deletion Addition Duplication Inversión Translocation
What is a mutation?
Change to the base sequence of DNA - caused by errors during DNA replication.
Some mutations can cause…
Genetic disorders - inherited disorders caused by abnormal genes or chromosomes.
What are hereditary mutations?
If a gamete has a genetic disorder or cancel and then it is fertilised, passed on to offspring.
Why do additions, duplications and deletions almost always cause a change in the amino acid sequence?
Because these change the number of bases in the DNA code - causes a frameshift so the triplet code is read in a different way.
How can mutagenic agents increase the rate of mutation?
- chemicals called base analogs can substitution a base, changing base sequence.
- chemicals can delete or alter bases.
- changing the structure of DNA which causes problems during DNA replication.
Mutations that occur after fertilisation…
Acquired mutations
What happens if mutations occur in genes that control the rate of cell division?
Causes uncontrolled cell division - resulting in a tumour (mass of abnormal cells)
Two genes which control cell division:
- tumour suppressor genes
- proto-oncogenes
How can tumour suppressor genes be affected?
If a mutation occurs in the DNA sequence, they can be inactivated.
This means the proteins they make can to be produced so cells divide uncontrollably.
What do Tumour suppressor genes do?
They slow cell division by producing proteins that stop cells dividing or cause them to self destruct.
What do proto-oncogenes do?
They stimulate cell division by producing proteins that make cells divide.
How can proto-oncogenes be affected?
If a mutation occurs in the DNA sequence and in it, gene can become overactive so cells divide uncontrollably.
What is a muted proto-oncogene called?
Oncogene
Malignant tumours
Cancers - grow rapidly and destroy surrounding tissues, can break off and spread to other parts via bloodstream or lymphatic system.
Benign tumours
Not cancerous - grow slower and are covered in fibrous tissue that stops cells invading other tissues, harmless but can cause blockages and put pressure on organs.
How do tumour cells differ from normal cells? (4)
- irregular shape
- nucleus is larger and darker
- different antigens
- divide by mitosis more frequently
What is methylation?
Why is it important?
Adding a CH3 group onto something - this is important for regulating gene expression, can control whether or not a gene is transcribed.
What happens when methylation is happening normally?
It plays a key role in many processes
But when it happens too much or too little, it becomes a problem.
Hypermethylation
When methylation happens too much
Hypomethylation
When methylation happens too little
What happens when tumour suppressor genes are hypermethylated?
The genes are not transcribed, proteins to slow cell division not made - cells grow uncontrollably.
What happens when proto-oncogenes are hypomethylated?
They act as oncogenes - increasing the production of proteins that encourage cell division - cell divides uncontrollably leading to tumour.
Increased exposure to oestrogen…
Increases a woman’s risk of developing breast cancer.
How does oestrogen contribute to the development of breast cancer? (3)
- oestrogen stimulate some breast cells to divide and replicate - more divisions increases mutations so more chance of cancerous cells.
- stimulating division means if cells do become cancerous, their rapid replication forms tumours.
- other research shows it may be able to introduce mutations directly to breast cells.
Genetic factors of cancer
Some cancers are linked to specific alleles - if you inherit it, more likely to get it
Environmental factors of cancer
Radiation
Smoking
Alcohol
High fat diet
Mastectomy
Removal of one or both beasts
Gene therapy
Where faulty alleles in a persons cells are replaced by working versions of the alleles
