Mutations Flashcards
What are mutations?
Errors made in the DNA sequence that are inherited. These errors can have deleterious side effects, no effect, or positive side effects for an organism
Give an example of a positive and negative mutation
Positive: the large size of the human brain as a result of mutation
Negative: mutation of CFTR gene resulting in CF can be inherited
What are the two types of mutations
Point mutation, chromosomal mutations
Describe point mutations
Mutations at a specific base pair in the genome
Describe chromosomal mutations
These mutations involve large segments of the DNA and are apparent at the chromosomal level
Occurs when large sections of chromosomes ar altered or shifted leading to change in the way the genes are expressed
What are the types of point mutation?
Silent: A mutation that doesn’t result in a change in the amino acid coded for and thus does not result in a phenotypic change. It usually occurs in the introns so they get cut out of the primary mRNA transcript. Also, due to the redundant nature of the genetic code, it normally codes for the same amino acid (wobble hypothesis)
Missense: Arises when a change in the sequence occurs leading to a different amino acid being placed in the protein sequence (ex. Sickle cell anemia)
Nonsense: A change in the DNA sequence that converts a codon for an amino aid into a termination codon (often lethal for the cell)
Frameshift: A change in the DNA sequence because one or more nucleotides are inserted or deleted that causes the reading frame of codons to change, resulting in different amino acids being incorporated into the polypeptide that will be defective
What are the causes of mutations?
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 (UV radiation, cosmic rays, certain chemicals, pesticides, viruses)
What are the types of chromosomal mutations?
Translocation: Involves the interchange 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 problems 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 don’t separate properly and the daughter cell ends up with unequal amounts of DNA
Review the types of point mutations (examples)
Read section 7.5 (340); pg. 345 1-8
