3.2.11 Mutation and Cancer Flashcards Preview

A-level Biology Oxford AQA > 3.2.11 Mutation and Cancer > Flashcards

Flashcards in 3.2.11 Mutation and Cancer Deck (42)
Loading flashcards...

What is a gene mutation?

Changes in DNA base sequence of chromosomes


Name 2 types of errors that occur

  • Substitution 
  • Deletion 


What is deletion?

When one base is deleted 

e.g. ATGCCT becomes ATCCT (G is deleted)


What is substitution?

When one base is substituted with another

e.g. ATGCCT becomes ATTCCT (G is swapped for T)


Name 3 types of substitution 

  • Nonsense mutation 
  • Missense mutation 
  • Silent mutation 


What is a nonsense mutation?

Occurs if base change = stop codon


What is a missense mutation?

Occurs if base change = different amino acids being coded for


What is a silent mutation?

Substituted base, although different = codes for same amino acid


Why will not all substitution mutations lead to a change in the amino acid sequence of a protein?

Due to the degenerate nature of genetic code, some amino acids are coded for by more than one DNA triplet


Why will deletions always lead to changes in amino acid sequence?

From point of mutation base sequence changes/causes frame shift


What do mutagenic agents do?

Increases the frequency of mutations


Give an example of a mutagenic agent

e.g. UV radiation, ionising radiation, some chemicals and some viruses


Mutations occur _____


e.g. when DNA is misread during replication


What are acquired mutations?

Mutations that occur in individual cells after fertilisation


Describe how mutations can cause a tumour

  1. If mutations occur in genes that control rate of cell division (by mitosis) = uncontrolled cell division
  2. Uncontrolled cell division = tumour (mass of abnormal cells)


What is cancer?

Tumours that invade and destroy surrounding tissue 


Name the 2 types of gene that control cell division

  • Tumour suppressor genes
  • Proto-oncogenes 


How can tumour suppressor genes be inactivated?

If mutation occurs in DNA sequence


When functioning normally, what do tumour suppressor genes do & how?

Slow cell division by producing proteins that stop cells dividing or cause them to self-destruct


Describe how a mutation may affect tumour suppressor genes & what this can lead to

  1. Mutation prevents transcription of gene
  2. Protein isn't produced so doesn't inhibit cell division
  3. No control of mitosis (cells divide uncontrollably) = tumour


How can the effect of proto-oncogene be increased?

If mutation occurs in DNA sequence


What is a mutated proto-oncogene called?



When functioning normally, what do proto-oncogenes do & how?

Stimulate cell division by producing proteins that make cell divide


Describe how a mutation may affect proto-oncogenes & what this can lead to

  1. Proto-oncogenes become oncogenes
  2. Oncogene stimulate rapid cell division without growth factor (divide uncontrollably = tumour)
  3. Oncogene cause production of excess growth factor


Tumours can develop for years without ______ _______ & can become ____ before they're ______

Tumours can develop for years without obvious symptoms & can become large before they're discovered


 Name the 2 types of tumours 

  • Malignant tumour (cancerous)
  • Begin tumours (not cancerous)


Describe malignant tumours

  • Mass of undifferentiated cells 
  • Uncontrolled cell division
    • Usually grow rapidly and invade and destroy surrounding tissues
  • Cells break off tumours and spread to other parts of body (in bloodstream and lymphatic system)


Describe begin tumours

  • Grow slower than malignant tumours & often are covered in fibrous tissues that stop cells invading other tissues
  • Often harmless but can cause blockages & put pressure on organs
  • Some benign tumours can become malignant


Name 6 ways tumour cells can differ from normal cell

  1. Irregular shape 
  2. Nucleus is larger and darker (& sometimes have more than 1 nucleus)
  3. Don't produce all proteins needed to function correctly
  4. Different antigens on their surface
  5. Don't respond to growth regulating processes
  6. Divide by mitosis more frequently


What are cancer treatments that target the cell cycle designed to do?

  • Designed to control rate of cell division in tumour cells by disrupting the cell cycle
  • This kills tumour cells 

Decks in A-level Biology Oxford AQA Class (41):