14 Questions
What is a mutation?
A change in the DNA sequences
What are the causes of spontaneous mutations?
Chemical instability of purine and pyrimidine bases
Which environmental factor can cause mutations?
UV light
Why don't all mutations result in visible changes in an organism?
Affected genes may still function
Which type of mutation can cause premature protein synthesis termination?
Nonsense mutations
What type of mutation can alter the codon and produce a different amino acid in the protein product?
Missense mutations
Which type of mutation can shift the reading frame and result in non-functional proteins?
Insertions and deletions
What can cause harmful phenotypes due to the insertion of multiple copies of a trinucleotide repeat?
Insertions and deletions
Which type of mutation can cause disruptions in the reading frame and lead to non-functional proteins?
Insertions and deletions
What type of mutation does not affect the protein and is not detected by sequencing the gene or its mRNA?
Silent mutations
Which mutation type alters the precise removal of introns during mRNA processing, leading to incorrect protein sequences?
Splice-site mutations
What mutation can disrupt a gene's function or create a hybrid gene?
Translocations
Which mutation type involves the transfer of a piece of one chromosome to a non-homologous chromosome?
Translocations
In which type of mutation can a purine or pyrimidine be replaced by another?
Transitions
Study Notes
- Mutations in gametes (egg and sperm) can be passed onto offspring, while mutations in body cells do not affect the next generation.
- Types of Mutations:
- Single-base substitutions (point mutations):
- Missense mutations alter the codon and produce a different amino acid in the protein product. Example: sickle-cell disease.
- Nonsense mutations change a codon to a STOP codon, causing premature protein synthesis termination. Example: Cystic fibrosis.
- Silent mutations do not affect the protein since many amino acids have multiple codons.
- Splice-site mutations interfere with the precise removal of introns during mRNA processing and alter protein sequence.
- Large-scale changes:
- Insertions and deletions can shift the reading frame and result in non-functional proteins.
- Trinucleotide repeat diseases, such as Fragile X Syndrome, can be caused by the insertion of multiple copies of the repeat.
- Single-base substitutions (point mutations):
- Single-base substitutions:
- A purine or pyrimidine can be replaced by another.
- Transitions (purine-purine or pyrimidine-pyrimidine) and transversions (purine-pyrimidine or pyrimidine-purine).
- Depending on the consequences, substitution mutations can be grouped as silent, missense, or nonsense mutations.
- Nonsense mutations cause the premature termination of protein synthesis and can be lethal or severe in phenotype.
- Silent mutations do not affect the protein and are not detected by sequencing the gene or its mRNA.
- Splice-site mutations alter the precise removal of introns during mRNA processing, leading to incorrect protein sequences.
- Large-scale changes:
- Insertions and deletions can disrupt the reading frame and lead to non-functional proteins.
- Trinucleotide repeat diseases can cause harmful phenotypes due to the insertion of multiple copies of the repeat.
- Fragile X Syndrome is an example of a trinucleotide repeat disease caused by the expansion of a CGG repeat.
- Translocations involve the transfer of a piece of one chromosome to a non-homologous chromosome and can alter the phenotype in various ways, such as disrupting a gene's function or creating a hybrid gene. The Philadelphia chromosome in chronic myelogenous leukemia (CML) is a result of a translocation.
Test your knowledge about mutation, its effects, and mutant organisms. Learn about how mutations can lead to changes in DNA sequences and the resulting differences in appearance, physiology, and behavior of mutant organisms compared to nonmutant ones.
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