Gene Mutations Flashcards
What happens as a result of gene mutations?
- change in the DNA base sequence of chromosomes
- may cause a different polypeptide
- new alleles form
How are most mutations described?
Harmful and Recessive
What causes mutations?
- incorrect pairing during DNA replication
- mutagenic pairing
Give some examples of mutagenic agents.
- High energy radiation
- High energy particles
- Chemicals, such as: nitrous oxide, benzene and tar
How does substitution act as a gene mutation?
It is the replacement of one or more bases by one or more different bases.
Substitution by a single base may lead to:
- a new triplet coding for a different amino acid which may produce a non functioning protein
- a functional protein still being produced
- same amino acid may be coded for due to the degenerate DNA code
- formation of a stop triplet
How does deletion act as a gene mutation?
The removal of one or more bases in a copied DNA sequence.
- results in a frame shift which alters all of the triplets from the point of deletion which forms a non-functional protein
Describe the effect of mutation on protein structure.
- DNA base sequence changes due to deletion/ substitution
- mRNA sequence in transcription changes
- tRNA molecules bring different amino acids to the different mRNA sequence
- So amino acid sequence ( primary structure) changes
- So secondary structure changes as hydrogen bonds form in different places
- So tertiary structure also changes as hydrogen, ionic and disulfide bonds form in different places
- If the protein is an enzyme, the active site shape changes
- Substrate is no longer complementary so will not bind
- ES complexes can not form and the enzyme becomes non-functional
How does addition affect the DNA base sequence?
One of more bases are inserted which cause a frame shift which can lead to the formation of a new protein
