Rucete ✏ Biology In a Nutshell
1. Point Mutations
- Occur when a single nucleotide in the DNA sequence of a gene is altered.
- Types of point mutations:
- Substitution: One nucleotide is replaced by another.
- Deletion: A nucleotide is removed.
- Insertion: An extra nucleotide is added.
- These mutations can change gene function, potentially leading to disease.
Example: Sickle-Cell Disease
- Caused by a point mutation in the gene for hemoglobin.
- Results in abnormally shaped red blood cells, which can lead to pain, anemia, and organ damage.
2. Aneuploidy
- Refers to a genome with extra or missing chromosomes.
- Caused by nondisjunction during meiosis.
Down Syndrome (Trisomy 21)
- Caused by an extra copy of chromosome 21 (three instead of two).
- Symptoms include intellectual disability, heart defects, and respiratory issues.
Turner Syndrome (XO)
- A condition where females have only one X chromosome instead of two.
- Leads to short stature, infertility, and other developmental abnormalities.
3. Chromosomal Aberrations
- Involve structural changes in chromosomes:
Duplication
- A segment of a chromosome is repeated.
- Can lead to developmental issues depending on the genes involved.
Inversion
- A chromosome segment is reversed end to end.
- May disrupt gene function if important genes are inverted.
Translocation
- A segment of one chromosome is moved to a different chromosome.
- Can be reciprocal (segments exchanged) or nonreciprocal (one-way).
- May lead to disorders or increase the risk of certain cancers.
Deletion
- A segment of a chromosome is missing.
- The severity depends on the size and genes involved in the deletion.
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Biology in a nutshell