Mutation, DNA Repair, and Maintenance of Genetic Information Flashcards
Define various types of mutation that occur in humans, including missense, nonsense, frameshift, germ-line, somatic, inversions, translocations, and silent mutations.
Missense - Altered amino acid - may affect protein function or ability
Nonsense - Stop codon-loss of expression/function
Frame shift - likely to result in premature termination with loss of function or expression
germline: a mutation that is passed to offspring
somatic - a mutation that can occur in any cell but not passed to children
inversions - a chromosome segment is clipped turned upside down and reinserted back into the chromosome
translocations - wen chromosome segments and genes change positions
silent mutation - when the amino acid remains unchanged
Predict the relative health risks generally associated with various types of human mutations.
Mutation - changes that may lead to disease
Polymorphism - locations in the genome in which differences exist
–many new mutations do not really affect health because mutations can occur in noncoding regions
–factors influencing mutant disease: environment, homozygous or heterozygous for allele, location of mutation (splice out or not), every cell (germline) or some cells (somatic)
Explain why DNA repair mechanisms are important, using disorders of DNA repair as examples.
Type of DNA repair:
Base excision repair (BER) - removes abnormal bases - colorectal cancer
Nucleotide excision repair (NER) - removes thymine dimers - Xeroderma pigmentosum
Post-replication repair - removal of double strand breaks - Breast Cancer
Mismatch Repair (MMR) - corrects mismatched bases - colorectal cancer
Describe the appropriate nomenclature for a mutation, given a wild-type and mutant mRNA sequence and a genetic code table
Missense - c.482G>A, p.Arg117His - Arginine to Histidine
Nonsense - c.1756G>T, p.Gly542X - Glycine to Stop
Explain mechanistically how telomeres are maintained in human cells and one way in which defects in this process related to aging & cancer.
Telomerase contains a RNA sequence that provides a template for the telomeric repeat sequences at the tips of chromosomes. Defects in Telomerase will make cells reach the Hayflick limit (limit on how many times a cell can divide) this will cause premature aging
