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Flashcards in Gene Mutation Deck (16):

Define mutation

Any change to the quantity or the structure of the DNA of an organism


What do mutations form the basis of?

Discontinuous variation


Define gene mutation

Any change to one or more nucleotide bases, or any rearrangement of the bases in DNA


Define the substitution of bases

Where a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base


Depending on which new base is substituted for the original base, there are three possible consequences. What are they?

A nonsense mutation, mis-sense mutation or a silent mutation


When does a non-sense mutation occur?

If the base change results in the formation of one of the three stop codons that mark the end of a polypeptide chain which means the protein cannot perform its normal function


When does a mis-sense mutation occur?

When the base change results in a different amino acid being coded for so the polypeptide will differ by one amino acid


When does a silent mutation occur?

When the substituted base, although different, still codes for the same amino acid as before, so the mutation will have no effect


How does a mutation occur by deletion?

A nucleotide is lost from the normal DNA sequence


What does a deleted nucleotide create?

A frame shift


What are mutagens?

Outside factors that increase the mutation rate


Give two examples of mutagens

High-energy radiation that can disrupt the DNA molecule and chemicals that can alter the DNA structure or interfere with transcription


In normal cells, what is the rate of cell division controlled by?

Proto-oncogenes which stimulate cell division and tumour suppressor genes that slow cell division


What can a gene mutation cause proto-oncogenes to mutate into?



How can oncogenes affect cell division?

The receptor on the cell surface membrane can be permanently activated so that cell division is switched on even in the absence of growth factors or the oncogene may code for a growth factor that is then produced in excessive amounts, again stimulating excessive cell division


What are the two types of tumour?

Malignant and Benign