20.5 & 20.6: Gene expression & cancer & genome projects Flashcards
Types of tumour
2
benign
malignant
Benign tumour
non - cancerous
Malignant tumour
cancerous
Benign tumour
growth rate and size
grow very slowly and can grow to a large size
Malignant tumour
growth rate and size
grow rapidly and can grow to a large size
Cell nucleus in a benign tumour
Relatively normal appearance
Cell nucleus in a malignant tumour
Often larger and appear darker due to an abundance of DNA
Benign tumour cells
Differentiated and produce adhesion molecules which makes them stick together and remain in the tissues from which they arise.
Malignant tumour cells
Become de-differentiated and don’t produce adhesion molecules
Metastasis
Forming of secondary tumours
Characteristics of a benign tumour
surrounded by a capsule and remain as a compact structure
Characteristics of a malignant tumour
not surrounded by a capsule and have finger like projections that can grow into the surrounding tissue
Effects of malignant tumour
often systemic effects such as weight loss and disease
Systemic
whole body
Treatment of malignant tumours
usually involves chemotherapy, radiotherapy and surgery
and more frequently reoccur after treatment
Treatment of benign tumours
surgery
Oncogenes
Mutations of proto-oncogenes
Protooncogenes
Stimulate a cell to divide when growth factors attach to a protein receptor on its cell-surface membrane. Which activates genes that cause DNA replication an cell division.
Reasons why the mutation of a protooncogene into an oncogene can permanently activate an oncogene
2
- Receptor protein on the cell surface membrane can be permanently activated so cell division occurs even without growth factors
- The oncogene may code for a growth factor that is produced in excessive amounts, again stimulating excessive cell division
Tumour suppressor genes
Slow down cell division, repair mistakes in DNA and trigger apoptosis.
Tumour suppressor genes mutation
switches it off/ inactivates it
stops inhibiting cell division
cells can grow out of control
Most cancers are
acquired not inherited
Hypermethylation
Increased methylation
Hypomethylation
Reduced methylation
Process by which hypermethylation may lead to cancer
Occurs in a specific region of tumour suppressor genes.
Leads to the tumour suppressor gene being inactivated.
Leads to increased cell division and formation of a tumour.
Oestrogen concentrations and breast cancer
Fat cells in breasts tend to produce more oestrogen after menopause. Oestrogen causes proto-oncogenes in breast tissue to develop into oncogenes which leads to development of a tumour.
