Chapter 3 Mutations Flashcards
Mutations
What are they
- Change in order of nucleotides
- Can be either somatic mutations where it occurs in the somatic cell. EG) all cells expect gametes. These only affect individuals. An example is cancer.
- Can be germline where it occurs in the sex cells/gametes. This mutation is passed onto the next generation.
Mutations
What can cause them
Errors in cell divide cause mutation
- Translation
- Transcription
- DNA replication
Types of mutations
What is a SNP
A single nucleotide is affected
Single nucleotide polymorphism
Types of mutations
Silent/synonymous mutations
▪ A silent/synonymous mutation occurs when substitution results in a codon that codes for the same amino acid.
→ There is no change in the DNA.
→ No change in the translated Amino Acid.
Types of mutations
Missense mutations
▪ A missense mutation occurs when substitution results in a change in one amino acid.
Types of mutations
Nonsense
▪ A nonsense mutation occurs when substitution creates a stop codon (ie. early termination).
→ leads to early termination of translation of the transcribed gene sequence.
Types of mutations
Insertions and deletions
▪ Insertions and deletions cause the addition or removal of a nucleotide.
Insertion is the addition of one or more nucleotides. Deletion is the loss of a nucleotide.
→ Usually results in a frame-shift mutation, which affects all codons ‘downstream’.
→ All codons from insertion or deletion will be nudged out by one.
→ This results in all the amino acids to be different from the original code.
Mutations in chromosomes
Deletions
The removal of a section of DNA
Mutations in chromosomes
Inversion
When a section of DNA is flipped/reversed
Mutations in chromosomes
Translocation
When a section of a chromosomes swaps with a section of a non-homologous chromosome
Mutations in chromosomes
Duplication
When a copy is made of a section
Effects of mutations on survival
Neutral mutations
▪ Neutral mutations occurs when the nucleotide is unchanged by the change in an amino acid
→ The survival of an organism is not affected.
→ Occurs with silent mutations.
→ It can sometimes occur with missense mutations if the new amino acid has similar properties to the original.
Effects of mutations on survival
Deleterious mutations
▪ Deleterious mutations disrupt the function of encoded proteins and impacts ability to survive.
→ This usually occurs with nonsense mutations with (usually) serious effects.
→ An organism can survive if they have a copy of the normal allele.
Effects of mutations on survival
Transposable
▪ Transposable elements cause death if occurring in the exon.
→ These are less harmful in introns and can be passed on if in gametes.
Effects of mutations on survival
Beneficial
▪ Beneficial mutations aid the survival of an organism.
→ Missense mutations can change the function of the original protein for the better.
EG: Having one allele of the sickle cell mutation prevents the catching of malaria.
→ Nonsense mutations may eliminate harmful proteins.
EG: Some people have nonsense mutations eliminate surface proteins needed by HIV to enter cells.
Causes of mutations
▪ Mutations can be spontaneous due to errors in cell division.
▪ Mutations can also be induced by either chemical or physical mutagens.
▪ According to mutation research:
→ mutations arise spontaneously;
→ environmental influences effect mutations rate;
→ mutations are persistent;
→ mutations usually mean a disadvantage (premature death means alleles spread in population).
▪ Mutations can be invisible, subtle or severe - rarely beneficial.
▪ The effect depends on whether the mutations are in somatic or germ-line cells (gametes).
Causes of mutations
Somatic cell mutations
▪ Somatic cell mutations occur only in affected body cells and any daughter cells produced by mitosis.
→ All other cells lack mutation.
→ Mutations usually build up, accelerate ell division and terminates apoptosis.
→ These mutations cannot be inherited.
Causes of mutations
Germ-line mutations
▪ Germ-line mutations affect gametes so it can be inherited.
→ If so, present in every cell of the offspring.
→ This often leads to developmental abnormalities that cause spontaneous abortion.
→ If birth occurs, offspring may be born with severe disorders.
→ If consistently passed on, a new allele has entered the population.
