Module 10 Flashcards
Point Mutations
Can be in the form of a missense, nonsense, silent, or frameshift mutation
Gene mutations outside coding regions:
- Promoter
- Regulatory element
- 5’/3’-UTR
- Splice recognition sequence
Position Effect
An alteration in the expression of a gene after it is transposed (changes position), it may either assume the expressivity of another gene under which promoter it lands under, or it may not be expressed if moved to heterochromatin/inactive sequence
Germ Line Mutations
Can occur directly on an egg or sperm cell, affects the entire zygote
Somatic Cell Mutations
Can occur within a single embryonic cell, as that cell proliferates a patch develops with the mutation
Lederberg & Lederberg Experiments
Studied resistance of E. coli to bacteriophage T1, discovered tonr gene conferring resistance only from specific colonies repeatedly, which supported their random mutation hypothesis
Spontaneous Mutations
Mutations with intracellular causes (ex. DNA replication errors)
Induced Mutations
Mutations caused by environmental agents (ex. chemical or physical mutagens)
Examples of Spontaneous Mutations:
- Depurination (removes purines, forming apurinic sites)
- Deamination (removes amino group from cytosine, which becomes uracil or thymine)
- Tautomeric Shift (T and G can convert to enol, A and C can convert to imino)
Trinucleotide Repeat Expasion (TNRE)
Causes some human genetic disease above a length limit for carriers, contain C and G and form hairpin during replication which lengthen the DNA strand
Mutagen
Agents altering DNA structure and causing mutations
Can be physical (ex. ionizing and non-ionizing radiation) or chemical (ex. base modifiers, intercalating agents, and base analogues)
Base Modifiers
Covalently modify nucleotide structure (C to U, A to H)
Ex. Nitrogenous mustards
Intercalating Agents
Contain flat, planar structure which form double helix that distorts helical structure of DNA to result in frameshifts
Ex. Proflavin
Base Analogues
Become incorporated into daughter strand during replication
Ex. 5-bromouracil is a T analogue
Ionizing radiation can cause ____
damage to DNA backbone and double stranded breaks