Mutations Flashcards
What is a mutation?
A mutation is a permanent change in the DNA sequence that can alter protein production and affect phenotype.
When do mutations typically occur?
Mutations usually happen during DNA replication or cell division, when the DNA strands are vulnerable to damage or errors in base pairing.
Can mutations be inherited?
Yes, if they occur in germline cells (sperm or egg), they can be passed on to offspring. Somatic mutations (in body cells) are not inherited.
What are the two major categories of mutations?
- Point Mutations – Affect a single nucleotide.
- Chromosomal Mutations – Affect large sections or the entire chromosome.
What are the three main types of point mutations?
- Substitution – One base is swapped for another.
- Insertion – A base is added.
- Deletion – A base is removed.
What are the possible effects of a point mutation?
• Silent Mutation – No change in the amino acid sequence.
• Missense Mutation – Changes one amino acid, affecting protein function.
• Nonsense Mutation – Creates a stop codon, truncating the protein.
What is a silent mutation?
A base substitution that does not change the amino acid sequence due to the redundancy of the genetic code.
Do silent mutations affect the protein?
No, because the new codon still codes for the same amino acid.
Example:
• Original DNA: GAA (Glutamic Acid)
• Mutated DNA: GAG (Glutamic Acid) → No effect.
What is a missense mutation?
A base substitution that changes one amino acid in the protein.
How does a missense mutation affect protein function?
It may cause the protein to malfunction, depending on the importance of the altered amino acid.
Example:
• Sickle Cell Anemia – A single missense mutation changes glutamic acid → valine in hemoglobin, causing sickle-shaped red blood cells.
What is a nonsense mutation?
A base substitution that creates a premature stop codon, leading to an incomplete protein.
How does a nonsense mutation affect the protein?
It results in a nonfunctional or severely shortened protein.
Example:
• Duchenne Muscular Dystrophy – A nonsense mutation creates a stop codon, preventing muscle protein production.
What is a frameshift mutation?
A mutation caused by insertion or deletion of a base, which shifts the reading frame of the genetic code.
How does a frameshift mutation affect protein synthesis?
It alters all codons downstream, drastically changing the amino acid sequence and producing a dysfunctional protein.
Example:
• Tay-Sachs Disease – A frameshift mutation in the HEXA gene disrupts enzyme function, leading to neurodegeneration.
What are chromosomal mutations?
Large-scale mutations that affect entire genes or chromosomes.
What are the five types of chromosomal mutations?
- Deletion – A section of a chromosome is lost.
- Duplication – A segment is copied multiple times.
- Translocation – A segment moves to another chromosome.
- Inversion – A chromosome segment flips upside down.
- Insertion – A segment from one chromosome is inserted into another.
Give an example of a disorder caused by a deletion mutation.
Cri-du-chat Syndrome – A deletion on chromosome 5 leads to intellectual disabilities and a distinctive cry.
Give an example of a disorder caused by a duplication mutation.
Charcot-Marie-Tooth Disease – Duplication of a gene on chromosome 17, affecting nerve function.
Give an example of a disorder caused by a translocation mutation.
Chronic Myeloid Leukemia (CML) – Translocation between chromosomes 9 and 22 forms the Philadelphia chromosome, leading to uncontrolled cell division.
What increases the likelihood of mutations?
Mutagens – physical, chemical, or biological agents that cause mutations.
What are examples of physical mutagens?
• UV Radiation – Causes thymine dimers, leading to DNA damage.
• X-rays & Gamma Rays – Create free radicals that break DNA strands.
What are examples of chemical mutagens?
• Cigarette Smoke (Benzopyrene) – Causes DNA adducts, leading to cancer.
• Asbestos – Induces chromosomal instability.
• Benzene – Damages bone marrow DNA.
What are examples of biological mutagens?
• Viruses (Hepatitis B, HPV) – Integrate into host DNA and cause mutations.
• Bacteria (H. pylori) – Causes stomach cancer through chronic inflammation.
How do mutations cause disease?
They disrupt normal protein function, leading to genetic disorders and cancer.
What are two well-known genetic diseases caused by mutations?
- Sickle Cell Anemia – Missense mutation in the hemoglobin gene.
- Cystic Fibrosis – Deletion of three bases in the CFTR gene, causing thick mucus buildup.
How do mutations lead to cancer?
• Oncogene Activation – Mutations turn normal genes into cancer-causing genes.
• Tumor Suppressor Gene Inactivation – Mutations prevent the suppression of cell growth, leading to uncontrolled division.
Are all mutations harmful?
No! Some mutations are beneficial and drive evolution.
What is the role of mutations in natural selection?
Mutations introduce genetic variation, allowing organisms to adapt to their environment. Beneficial mutations are passed down through generations.
