Gene expression Flashcards
What is cancer
Mutations in genes that cause uncontrolled mitosis resulting in a tumour
Properties of a benign tumour
Can grow large but at a slow rate
cannot spread by metastasis
surrounded by a capsule
contain adhesion molecules to remain compact
localised
properties of malignant tumour
grow large rapidly
can spread by metastasis
develop their own blood supply
need supplementary treatment, chemo or radiotherapy
Three causes of tumour formation
Hypermethylation of tumour supressor genes
hypomethylation of oncogenes
increased oestrogen conc in by fat cells in breast tissue
What do oncogenes do and how can they cause cancer
code for a protein that causes DNA replication + mitosis
can be permanently switched on causing excessive cell division
hypomethylation increases expression as chromatin is less condensed
What do tumour suppressor genes do and how can they cause cancer
code for a protein that inhibits cell division and causes apoptosis
mutation can inhibit apoptosis and stimulate cell division
hypermethylation limits genes transcription so tumours can form as cell division can become uncontrolled and apoptosis is inhibited
How does oestrogen lead to cancer
production stops at menopause
fat cells in breast tissue produce oestrogen
oestrogen activates transcription factors which can cause transcription of oncogenes
formation of tumour leads to increased oestrogen product and increases tumour size and attracts white blood cells
What are the types of silent mutations
Where a base substitution does not change the amino acid sequence as the genetic code is degenerate
a mutation that occurs in non coding regions of DNA will not be translated into the amino acid sequence so no change in sequence
a mutation that causes a change in the tertiary structure of the protein, but has no major effect on the organism
What is an insertion and deletion mutation in DNA sequence what does it cause
one or more nucleotide pairs are inserted into the DNA sequence
one or more nucleotide pairs are deleted from the DNA sequence
both cause frameshifts in the DNA base sequence
(insertion right)
(deletion left)
this will change the amino acid sequence of a polypeptide
What is a duplication mutation
One or more bases are repeated and will cause a frameshift
same effect as insertion
What is an inversion mutation
a group of bases become separated from the dna base sequence and rejoin in reverse order
this changes the amino acid sequence and therefore primary + tertiary structure of protein
What is a translocation mutation
when a group of bases become separated on one chromosome and are inserted into the DNA sequence on another chromosome
leads to a significant effect on phenotype as different genes on different chromosomes
Causes of the DNA mutations
Spontaneous errors during DNA replication
chemical mutagens such as alcohol, tobacco, asbestos
ionising radiation - UV, x rays, alpha, beta
What are stem cells
undifferentiated cells that can continually divide and become specialised
4 types of stem cells
totipotent
pluripotent
multipotent
unipotent
