Study Unit 5 Flashcards
Mutation and genetic variation
Neurofibromatosis type 1 is caused by various mutations, including point mutations, deletions, and insertions in the NF1 gene. These mutations lead to the loss of function of neurofibromin, a tumor suppressor, causing the formation of benign and malignant tumors along nerves.
Genotype is the genetic makeup of an individual, while phenotype is the expression of the genotype.
What are the different types of mutations and their effects?
Mutations can be neutral, beneficial, or harmful. They include point mutations, insertions, deletions, and movement of transposable elements.
What are point mutations and their types?
Point mutations are changes in a single nucleotide. Types include synonymous (silent), nonsynonymous (missense), and nonsense mutations.
What is a synonymous (silent) mutation?
A mutation where there is no change in the amino acid in the protein, thus having no effect on the phenotype.
What is a nonsynonymous (missense) mutation?
A mutation that changes the amino acid sequence of a protein, potentially altering its function.
What is a nonsense mutation?
mutation that introduces a premature stop codon in the mRNA, resulting in a truncated, nonfunctional or unstable protein.
What are frameshift mutations?
Mutations caused by the insertion or deletion of one or two base pairs, shifting the reading frame and altering the entire downstream amino acid sequence.
What is the difference between frameshift and in-frame insertions/deletions?
In-frame insertions or deletions involve multiples of three bases and do not alter the reading frame, only adding or removing amino acids.
Give an example of a harmful mutation.
A mutation in the HTT gene increases glutamines, leading to Huntington’s disease.
Give an example of a beneficial mutation.
Lactase persistence in some adults allows continued digestion of lactose, improving survival and reproduction.
What is the difference between somatic and germ-line mutations?
Somatic mutations occur in nonreproductive cells and are not passed to offspring, while germ-line mutations occur in reproductive cells and are heritable.
What are the two classifications of mutations?
Small-scale mutations include single base-pair changes and frameshift mutations. Large-scale mutations include chromosome-level changes.
What are transposable elements?
DNA sequences that can change positions within the genome, potentially causing or reversing mutations and altering the cell’s genome size.
Who discovered transposable elements and how?
Barbara McClintock discovered transposable elements by studying the mutation in corn that resulted in yellow kernels due to the insertion of these elements.
What are some examples of chromosomal level mutations?
Examples include deletions, duplications, inversions, and reciprocal translocations.
What are the different DNA repair mechanisms?
DNA repair mechanisms include postreplication mismatch repair, base excision repair, and nucleotide excision repair.
How does postreplication mismatch repair work?
Mismatch repair involves recognizing and removing mismatched bases that alter the DNA double helix shape, followed by replacement with the correct bases.
How does base excision repair differ from nucleotide excision repair?
Base excision repair removes specific chemically modified bases, while nucleotide excision repair removes larger sections of mismatched or damaged DNA.
What types of damage does nucleotide excision repair address?
It removes multiple mismatched bases or bulky lesions, such as thymine dimers caused by UV damage.
What are some key concepts related to mutation and genetic variation?
Key concepts include the role of mutations in genetic variation, types of mutations, and DNA repair mechanisms.
