Topic 8 - Control Of Gene Expression Flashcards
What is a mutation and name the types of mutations
- changes base sequence of dna and affects structure and function of proteins and can cause genetic disorder
- substitution
- deletion
- substitution
- addition
- duplication - one or more bases repeated
- degenerate - no change on amino acid
- inversion - base sequence reversed
- translocation - base sequence moves from one loci on the gene to another
How can mutations affect proteins
- change amino acid sequence
- change tertiary structure
- change function or cause it to not work properly
Hereditary mutation
Mutation in gamete that’s developed in the fertilised foetus
- not all are harmful
Silent mutation
Degenerate - no change due to more than one base sequence that can code for the same amino acid
- can be caused by substitution
Frameshift
Additions, deletions or duplications cause framshift
- change in all amino acids from the point of the mutation
Mutagenic agents
- increase rate of mutation
- ultraviolet radio action
- Ionising radiation
- chemicals
How do mutagenic agents increase rate of mutations
- act as a base - substitution and changing base sequence
- altering bases - some chemical delete or alter bases
- change structure of dna - cause problems during dna replication
How do mutations lead to cancer
Uncontrolled cell growth and division leading to a tumour
Acquired mutations
Mutations in individual cells after fertilisation (in adulthood)
Tumour
Invade and destroy surrounding tissue
Types of genes controlling cell division?
Tumour suppressor genes
Proto-oncogenes
- mutations in these genes causes cancer
TSG
Tumour suppressor gene
- inactivated if mutation occurs in dna sequence
- function = to slow cell division (and cause cells to self-destruct)
- mutation in TSP = no protein produced and cell divided uncontrollably causing tumour
- breaks - if brakes not working, division can’t be stopped
Proto-oncogene
- mutated POG = oncogene
- effect of POG increased if mutation in dna sequence
- normal function = stimulates cells division by producing proteins that make cells divide
- mutation overactives POG stimulating uncontrolled division leading to tumour
- accelerator - if mutation occurs acceleration will increase
Malignant
Rapid growth
Invade and destroy surroundings tissue
Cells can break off tumour and spread into blood and lymph systems all around the body
Benign
Not cancerous
Slower growth
Fibrous tissue surrounding it stops invasion of other tissues
Harmless
Can cause blockages and increased pressure
Can become malignant
How are tumour cells different to normal cells
- irregular shape
- larger darker nucleus
- don’t produce all proteins needed to function correctly
- different antigens on surface
- don’t respond to growth regulating processes
- ## Divide by mitosis more frequently
Methylation
Adding methyl groups
-CH3
Methylation of DNA
- regulates gene expression
- control if a gene is transcribed (copied form mRNA)/ translated (turned into protein) or not
- normal body function at normal rate
HypERmethylation
- methylation happening too much
HypOmethylation
Too little methylation
Abnormal methylation
Hyp(er/o)methylation
- growth of tumours
TSG hypERmethylated
- genes not transcribed
- proteins to slow division not made
- uncontrolled division
- tumour develops
HypOmethylation of POG
- act as oncogenes
- increased production of genes encouraging cell division
- uncontrolled division stimulated
- formation of tumours
Increased exposure to oestrogen
- increase risk of breast cancer
- cause earlier menstruation or later menopause
