Mutations Flashcards
Review Mutations Examples worksheet
Define mutation
An error made in the DNA sequence that is inherited. These errors can have deleterious side effects, no effects, or positive side effects for an organism
Give an example of a positive and negative side effect
Negative: mutation of CFTR gene resulting in cystic fibrosis can be passed from parent to child
Positive: the large size of the human brain evolved as a result of mutations
What are the two categories of mutations?
Point mutations: at a specific base pair in the genome
Chromosomal mutations: involve large segments of DNA and are apparent at the chromosome level
What are the types of point mutations
Silent: does not result in a change in the amino acid coded for and therefore does not cause phenotypic change. Usually occurs in the introns and get cut out of the primary mRNA transcript. Also the redundant nature of the genetic code means an error in the third base pair of a codon usually codes for the same amino acid.
Missense: arises when a change in the base sequence of the DNA alters a codon, leading to a different amino acid being placed in the protein sequence (ex. Sickle cell anemia)
Nonsense: a change in the DNA sequence which converts a codon for an amino acid into a termination codon (often lethal for cell)
Frameshift: a change in the DNA sequence because one or more nucleotides are inserted or deleted that causes the reading frame of the codons to change, resulting in different amino acids being incorporated into the polypeptide that will be defective
What are the causes of genetic variation?
Spontaneous: occur without chemical change or radiation but as a result of an error made in DNA replication
Mutagenic agents: agents that cause a mutation (ex. UV radiation, cosmic rays, certain chemicals, pesticides)
What are the five types of chromosomal mutations?
Translocation: involves the interchanging of large segments of DNA between two different chromosomes
Inversion: occurs when a region of DNA flips its orientation with respect to the rest of the chromosome. This can lead to the same problem as translocation.
Deletion: occurs when large regions of a chromosome are removed. This leads to a loss of genes
Duplication: occurs when regions of chromosomes are doubled
Non-disjunction: during meiosis, the homologous chromosomes dont separate properly and the daughter cells end up with unequal amounts of DNA
