Question

how the dna mutation (substitution, insertion, or deletion) contributes to the trait

Explanation:

1. Substitution Mutation: A single - base pair in DNA is replaced by another. This can change the codon (a sequence of three nucleotides that codes for an amino acid) during translation. For example, in sickle - cell anemia, a substitution mutation in the gene for hemoglobin changes the codon for glutamic acid (GAG) to a codon for valine (GTG). This change in the amino acid sequence of hemoglobin leads to the production of abnormal hemoglobin molecules, which cause red blood cells to become sickle - shaped. These abnormal red blood cells have reduced oxygen - carrying capacity and can get stuck in blood vessels, leading to the symptoms of sickle - cell anemia.
2. Insertion Mutation: One or more nucleotide bases are added to the DNA sequence. This causes a frameshift mutation if the number of inserted bases is not a multiple of three. A frameshift mutation changes the reading frame of the genetic code. For instance, if a single nucleotide is inserted into a gene that codes for a protein, all the codons downstream of the insertion will be read incorrectly. This can lead to a completely different amino acid sequence in the resulting protein. If the protein is involved in a particular trait (such as an enzyme involved in metabolism), the non - functional or abnormal protein produced due to the frameshift can alter the trait. For example, in some forms of cystic fibrosis, insertion mutations can disrupt the normal structure and function of the CFTR (cystic fibrosis transmembrane conductance regulator) protein, affecting ion transport across cell membranes and leading to the characteristic symptoms of the disease.
3. Deletion Mutation: One or more nucleotide bases are removed from the DNA sequence. Similar to insertion, if the number of deleted bases is not a multiple of three, it causes a frameshift mutation. The reading frame of the genetic code is shifted, and the resulting protein may be non - functional or have altered function. For example, in some cases of Duchenne muscular dystrophy, deletions in the dystrophin gene lead to a non - functional dystrophin protein. Dystrophin is important for maintaining the integrity of muscle cell membranes, so the absence of functional dystrophin leads to muscle degeneration and the symptoms of the disease. If the mutation is in a gene related to a visible trait (like eye color - related genes), it can also alter the production of pigments or other molecules involved in determining the trait.

Answer:

• Substitution: Alters codon, may change amino acid (e.g., sickle - cell anemia), affecting protein function and trait.
• Insertion: Can cause frameshift (if not multiple of 3), changes protein sequence, altering trait (e.g., some cystic fibrosis cases).
• Deletion: Can cause frameshift (if not multiple of 3), disrupts protein function, affecting trait (e.g., some Duchenne muscular dystrophy cases).