Gene expression + cancer and using genome projects

Question 1

What is cancer?

Answer 1

Cancer can result in mutations in genes that regulate mitosis
If these genes mutate + non-functioning proteins are made, then mitosis is not regulated and it results in cell uncontrollable division and creation of tumour

Question 2

Characteristics of benign tumours

Answer 2

• Can grow very large but at a slow rate
• Non-cancerous as they produce adhesive molecules sticking them together + to a particular tissue so it can’t move
• Surrounded by capsule so remain as a compact structure so can’t spread around the body, so can be removed by surgery + rarely return
• Impact is localised
• Often not life-threatening, depending on tumour location

Question 3

Characteristics of malignant tumours

Answer 3

• Grow large rapidly + are cancerous
• Cell nucleus becomes large + cell can become unspecialised again
• Cells do not produce adhesive layer or capsule so instead metastasise, meaning the tumour breaks off + spreads to other tissues in the body
• Not surrounded by a capsule so can grow finger-like projections into surrounding tissues + develop its own blood supply
• Can be life-threatening
• Removal usually involves radiotherapy or chemotherapy as well as surgery
• Recurrence is more likely

Question 4

How do tumours develop?

Answer 4

Tumours develop due to a gene mutation in either:
- the tumour suppressor gene and/or oncogene
- abnormal methylation of tumour suppressor genes + oncogenes
- increased oestrogen concentrations

Question 5

Explain the role of oncogenes in the development of tumours

Answer 5

Oncogenes are mutated versions of a proto-oncogene, which creates a protein involved in the initiation of DNA replication + mitosis cell division when the body needs new cells
Oncogene mutations can result in this process being permanently activated to make cells divide continually so tumour develops

Question 6

Explain the role of tumour suppressor genes in the development of tumours

Answer 6

These genes produce proteins to slow down cell division + to cause cell death if DNA copying errors are detected
A normal tumour suppressor gene maintains normal rates of cell division + so prevents the formation of tumours
If a mutation results in the tumour suppressor gene not producing the proteins to carry out this function, then cell division could continue + mutated cells would not be identified + destroyed

Question 7

Explain the role of abnormal methylation in the development of tumours

Answer 7

Links to the control of transcription - methylation can cause a gene to turn on or off
Tumour suppressor gene could become hypermethylated (increased number of methyl groups attached to it). This results in gene being inactivated + becomes turned off, leading to increased cell division + formation of tumour
Oncogene may be hypomethylated, reducing the number of methyl groups attached. This results in the gene being permanently switched on (activated) hence formation of tumours

Question 8

Explain the role of increased oestrogen concentration in the development of tumours

Answer 8

• Oestrogen is produced by the ovaries to regulate the mestrual cycle but after the menopause this stops
• Instead, fat cells in the breast tissues can produce oestrogen - this is linked with causing breast cancer in women post-menopause
  This can result in a tumour being produced which can result in more oestrogen being produced, increasing the tumour size + attracts WBC’s which can increase the tumour size further
  This could be because oestrogen can activate a gene by binding to a gene that initiates transcription + if this is a proto-oncogene, it is permanently turned on + activating cell division

Question 9

What is the genome?

Answer 9

The entire genetic material of an organism in the nucleus of a cell

Question 10

What is genome sequencing?

Answer 10

Sequencing a genome means working out the DNA base sequence for all the DNA in a cell
Sequencing methods are continuously being improved + updated and has become automated

Question 11

What can the knowledge of genomes be used for?

Answer 11

• Simpler organisms like prokaryotic cells (bacteria), don’t contain introns in their DNA. This means the genome can be used directly to sequence the proteins that derive from the genetic code ( proteome) of organism
  This is useful for the identification of potential antigens for use in vaccination production
• More complex organisms, eukaryotes, have introns + regulatory genes in their DNA so the genome can’t easily be used to translate the proteome