3:Basal Cell Carcinoma

Question 1

Explain the difference in biological effect in an oncogene vs. a tumor suppressor gene

Answer 1

both play roles in development/progression of cancer.
Oncogenes when mutated/overexpressed drive uncontrolled growth of cells= cancer. Mutations in proto-oncogenes result in ‘gain of function’ effect. Genes activity increases compared to norm. This leads to overexpressed protein production– abnorm cell growth.

Tumor suppressor genes normally function to inhibit cell proliferation + promote cell death. Mutations lead to ‘loss of function’ effect= gene’s ability to suppress tumor growth decreases. As a result, gene no longer regulates cell growth, division, DNA repair= increased tumour formation.

E.g. oncogene mutation= HER2
tumour sup. gene mutation= BRCA1

Question 2

What is a nonsense mutation and what is the effect of this type of mutation on protein product

Answer 2

nonsense mutation= single base pair change in DNA sequence that results in a stop codon. Results in a truncated protein that may function incorrectly or may have no function depending on where the stop codon is introduced

e.g. can cause muscular distrophy, CF

Question 3

List processes a tumour suppressor gene inhibits

Answer 3

• apoptosis (a regulated cell death which eliminates cells carrying mutations)
• DNA repair
• cell cycle control (which allows cell carrying mutations to carry on dividing)

A mutation in a tumour suppressor gene results in a loss of function in these cellular processes

Question 4

Oncogenes promote unregulated:

Answer 4

• cell growth,
• cell division
• cell migration
• angiogenesis

there is therefore a gain in function in these cellular processes

Question 5

Identify FOUR histological alterations which commonly occur in epithelial cancers

Answer 5

• Hyperchromatic nuclei
• Tumour giant cells
• Abnormal mitoses
• Increased mitotic figures
• Prominent nucleoli
• Abnormal spindle formation
• Pleiomorphic nuclei
• Increased nuclear:cytoplasmic ratio
• Cells with a small amount of cytoplasm

Question 6

what 3 layers is the skin made up of

Answer 6

epidermis, the dermis and the hypodermis

Question 7

Identify the epithelial cell type found in the stratum corneum AND describe its functions

Answer 7

The stratum corneum (keratin layer) contains a keratinized layer of dead stratified squamous cells which serves as a protective layer + also allows for the regulation of water loss by preventing internal fluid evaporation

Question 8

Identify the epithelial cell type found in the stratum spinosum{helps make your skin flexible and strong} AND identify the type of intercellular junction which hold these cells together.

Answer 8

The stratum spinosum (prickle cell layer) is made up of several layers of keratinocytes connected by desmosomes

stratum spinosum is between the stratum basale and granulosum layers

Question 9

define desmosome

Answer 9

Desmosomes are adhesive intercellular junctions that mechanically integrate adjacent cells

Question 10

Why are darker skinned people at less risk of developing basal cell carcinoma?

Answer 10

Darker skinned people have more of the brown pigment melanin which absorbs UVB radiation and so protects the nuclei of adjacent keratinocytes and therefore protects the cells from mutational damage

Question 11

identify the mutation

GCA —-> GGA

Answer 11

point mutation

Question 12

identify the mutation

CCA—->TTA

Answer 12

Mutated dipyrimidines