Mutation and cancer

Question 1

Mutation -

Answer 1

Mutation - a sudden change in the amount or arrangement of the genetic material in the cell.

Question 2

Discontinuous variation

Answer 2

Discontinuous variation - variation shown when the characters of organisms fall into distinct categories. (limited number of possible values)

• mutations in body cells are not passed onto the next generation
• mutation during formation of gametes may be inherited, producing differences between individuals
• so mutations are the basis of discontinuous variation

Question 3

Non-sense mutation

Answer 3

Non-sense mutation
- substitution leads to the formation of a stop codon
- production of a polypeptide stopped
- final protein would be significantly different and wouldn’t perform its normal function

Question 4

Missense mutation

Answer 4

Missense mutation
- substitution results in a different amino acid being coded for
- the polypeptide produced will differ in a single amino acid
- the significance of the difference depends on the role of the amino acid, could change the whole structure

Question 5

Silent mutation

Answer 5

Silent mutation
- substituted base codes for the same amino acid
- due to genetic code being degenerate
- no effect on the protein

Question 6

Substitution of bases, types of mutation

Answer 6

• non-sense
• missense
• silent

Question 7

Deletion of bases

Answer 7

• results in a “frame shift”
• the polypeptide chain is entirely different
• different tertiary structure / non-functional protein

Question 8

Mutagenic agents

Answer 8

Mutagenic agents - factors that increase mutation rate
e.g., high energy radiation or chemicals that alter DNA structure

Question 9

Mutation adv and disadv

Answer 9

mutations in gametes
+ genetic diversity
- organisms less suited for environment
mutations in body cells
- disrupt normal cellular activities, e.g. cell division

Question 10

Role of proto-oncogenes

Answer 10

porto-oncogenes stimulate cell division
- by attaching to the receptor protein on the cell surface membrane and switching on genes for DNA replication through relay proteins

1. mutation in a proto-oncogene
2. formation of an oncogene
3. receptor protein permanently activated / oncogene codes for a growth factor
4. stimulate excessive cell division
5. tumour formation

Question 11

Benign vs malignant tumours

Answer 11

Benign tumours - do not spread to other pats of the body
Malicious tumours - cancerous cells invade nearby tissues, spreading to other parts of the body, forming further tumours

Question 12

Role of tumour suppressor genes

Answer 12

tumour suppressor genes inhibit cell division

1. mutation in a tumour suppressor gene
2. tumour suppressor gene is inactivated
3. stops inhibiting cell division
4. mutant cells divide rapidly forming tumours