Genetics unit 4: Mutations

a heritable change in DNA structure

define mutation

one nucleotide is changed, added, or removed 

what is a point mutation

when a purine is switched with a purine or a pyrimidine is switched with a pyrimidine

what is a transition mutation

transition, transversion, insertion, deletion

what are the 4 different kinds of point mutations

when a purine is switched for a pyrimidine or vice versa 

what is a transversion mutation 

mis-pairing, insertion of base analogs, or chemical mutagens

what causes transversion mutations

missense, nonsense, sense

what are the three categories of mutation that point mutations cause

nonsynomymous mutation

what is another name for a missense mutation

synomymous mutation

what is another name for a sense mutation

conservative and nonconservative

what are the two types of missense mutations

the point mutation results in a chemically similar amino acid that may function similarly to the original and have little effect

what is a conservative missense mutation

the point mutation results in a chemically dissimilar amino acids that may affect tertiary or quaternary protein structure and function

what is a nonconservative missense mutation

a point mutation that results in 1 incorrect codon and 1 incorrect amino acid

what is a missense mutation

a point mutation that results in the creation of a stop codon that terminates protein synthesis and often renders the protein nonfunctional

what is a nonsense mutation

a point mutation that results in the same amino acid being created through wobble and is usually a silent mutation 

what is a sense mutation

they remove or add a single nucleotide causing a frameshift that changes all codons after it causing a large impact

what is important about insertions and deletions

indel mutations

what is another name for insertions and deletions

northern and western blotting 

how can we visualize mutations 

non coding regions

where do the majority of mutations occur

non coding regions often participate in regulatory processes which if impaired can have negative impacts

how can mutations have an effect if they are in non-coding

mistakes in DNA replication, spontaneously, environmental influences

what are the 3 things that cause mutations to occur

tautomerizaton, Syn vs anti conformation (flipping around glycosidic bind), H2O acting as a bridge

what are the three mechanisms that cause mismatches in DNA replication 

H-bonding properties of the base

What do mutation mechanisms during DNA replication alter

Base analogs are molecules that are similar in structure to nucleotides that sometimes get mistakenly added to DNA during replication and cause mutations

what is Base analog incorporation and when does it occur

Deamination, Depurination/Depyrimidination, Oxygen radical damage 

what are the three kinds of spontaneous DNA mutation

because the primary amino groups of nucleic acid bases are unstable they can be converted to keto groups (by the removal of an amine group) and pair incorrectly

what is oxidative deamination

C changes to U and pairs with T, A changes to hypoxanthine and pairs with C, G changes to Xanthine and still pairs with C

what are the pairing rules for oxidative deamination

The glycosyl bond linking DNA bases with deoxyribose is unstable and purines/pyrimidines are lost creating an AP site that is often replaced with an A or removed from the DNA.

What is Depurination/Depyrimidination 

Depurination is more common because the purines create weaker bonds

which is more common and why: Depurination or Depyrimidination 

nitrous acid formed from nitrites reacting with stomach acid causing oxidative deamination, alkylating agents add methyl or ethyl groups to bases and change pairing properties, Intercalating agents like ethidium bromide distort the helix causing frameshift mutations

what are some examples of chemical mutagens and their effects

UVC 180-290, UVB 290-320, UVA 320-visible

what are the three types of UV light and thier wavelengths

germicidal, most energetic and lethal uv light, not found in sunlight because it is absorbed by ozone 

what is UVC light 

major lethan/mutagenic fraction of sunlight

what is UVB light

near uv, has negative effects because it creates oxygen radicals but produces less pyrimidine dimers that UVB and is less lethal

what is UVA light

A and B

which two UV lights cause most common damage to human DNA

causes dimers to form between adjacent T bases or adjacent T and C bases on DNA creating a cyclobutyl ring that links the adjacent nucleotides and interferes with base pairing blocking DNA replication

how does Uv light cause damage to DNA

e coli

what is the model system for understanding DNA repair mechanisms

Mismatch, Direct, and Excision repair 

what are the three main types of DNA repair

fixes pyrimidine dimers caused by things like UV damage

what is direct repair

Base and Nucleotide excision repair (BER and NER)

what are the two types of excision repair

fixes abnormal bases like uracil, hypoxanthine, and alkylated bases

what is Base excision repair 

fixes large structural changes and helix distortions like pyrimidine dimers and bulky base adducts

what is Nucleotide Excision repair

fixes mismatches

what does mismatch repair do….

Mutations that are not displayed in the phenotype because they do not change the amino acid created 

what are silent mutations