Chapter 15 Flashcards
Point mutations
A change in one or a few base pairs
Somatic mutations
mutant characteristics that only affect the individual (not heritable)
Germ-line mutations
Transmitted through gametes (heritable)
transition mutation
A mutation from one purine to another purine (or pyrim to pyrim)
Transversion mutation
a mutation from a purine-pyrimidine base pair to a pyrimidine- purine base
Missense mutation
Base pair change that causes a different amino acid
Nonsense mutation
base pair change that alters a base pair to a stop codon
Neutral mutation
Changes a base pair to produce a different amino acid, but there is no change in function
frameshift mutation
an addition or deletion of one base pair which causes everything downstream to change
Deletion (FSM)
removal of a base pair
Forward mutation
changes at a wild type gene to a mutant gene
Insertion (FSM)
addition of a base pair
Silent Mutation
When a base pair is altered but the same amino acid is produced
Reverse mutation
Changes mutant gene at the same site so it functions same as the wild type
True reversion
the amino acid is rewritten back to the wild type
Partial reversion
amino acid is reverted to different aa but protein function is partially or fully restored
suppressor mutation
mutation that minimizes effects of another mutation
Intragenic suppressor
occurs in same gene as other mutation
Intergenic mutation
mutation in another gene which results in a second mutation
Nonsense suppressors
two mutations occur (one in gene, other in tRNA)
Sickle cell mutation
differ in a single amino acid (sixth amino acid from one end)
spontaneous mutations
all point mutations occur spontaneously and are naturally occuring
Tautomeric shift
protons are transferred from one site to another (isomers that readily interconvert)
Tautomeric shift for A and C
cause the NH2 group on A and C to shift
Tautomeric shift for G and T
Causes a shift in the COH group
Base tautomers
Causes T-G to bind and A-C
Induced Gene mutations
are caused by the environmental factors
What is a large cause of mutation
food preservatives
Ionizing energy
so strong that is knocks e- out of atomic shell and destroys covalent bonds
A form of Non-ionizing radiation
UV light
Deinococcus Radiodurans
A species of Archae that can survive chronic ionizing radiation
How much radiation is naturally occuring
81% (56% is radon gas)
Photoreactivation Repair
A type of direct reversal repair that requires light and IS NOT found in humans
Photolyase
light activated enzyme that splits dimers apart
Nucleotide excision repair
Type of excision repair that repairs pyrimidine dimers , does not require light to work
What do UvrA and UvrB do
it scans for DNA damage
Chemical Mutagens
naturally occurring and synthetic substances that cause mutations
Base Analogs
require replication to induce mutation (look very similar to nitrogenous bases)
Example of base analog
5-Bromouracil
What base does 5-BU imitate in its normal state
Thymine
What base does 5-BU imitate in its rare state
Cytosine
Base modifying agents
changes structure of base
Types of base modifying agents
- Deaminating agent ( nitrous acid)
- Hydroxylating agent (hydroxylamine)
- Alkylating agent (methylmethane)
What do deaminating agents do
lead to the loss of an amino which affects base pairing
What do Hydroxylating agents do
They lead to the addition of a hydroxyl group and prevent bases from pairing
what do alkylating agents do?
they lead to the addition of a methyl group which affects bonding
intercalating agents
insert in between DNA bases
Example of intercalating agent
Ethidium Bromide (remember Prof eyes)
Direct reversal repair
corrects damage without breaking the phosphodiester bonds, which preserves more genetic material
What activates Photolyase
Blue light
DNA Polymerase Mismatch repair
During replication, DNA polymerase can go back and detect mismatched base pairs and fix them
Excision repair
DNA damage is excised from one stand, complement is used as a template to produce a corrected strand
Types of excision repair
- Base excision repair
- Nucleotide excision repair
- methyl directed mismatch repair
Base excision repair
repairs damaged single bases
Methyl directed mismatch repair
recognizes base pair mismatches remaining after replication
