types of mutations

mutation

change in genetic code

purines

As and Gs

pyrimidines

Ts and Cs

point mutation

change in 1 nucleotide

transition

change nucleotide but not the class of nucleotide

transversion

purine to pyrimidine or back, changes class on nucleotides

silent mutation

changes nucleotide or DNA, but doesnt change amino acid and does affect structure

missense mutation

G to C, transversion, change amino acid

nonsense mutation

stop codon → stop translation

nothing will be made or read after this point

frameshift

3 nucleotides is 1 codon

reading by frame of three

insertion

shifts codon frame so it could be off by 3s

deletion

one or more nucleotide is removed

mismatched repair pathway

detects mismatched base pairings

mostly occurs in highly repetitive regions

base excision repair

detects distorted bases

caused by carcinogens/mutagens

age affect: cancer and cognition

Nucleotide excision repair

detects DNA adducts (anything that can chemically bind to DNA) or bulky damage from uv

more common in fair or light skin

homology-directed repair (HDR)

repairs double stranded breaks

can only occur when sister chromatid is present

→ no loss of genetic material

what is the defect of HDR

BRCA ½ (can increase likelihood of breast cancer)

what is the defect of nucleotide excision repair

xeroderma pigmentosum

what is the defect for mismatched repair pathway

lynch syndrome

what is mismatched repair pathway repaired by

polymerase delta

what is base excision repair repaired by

polymerase beta (drop in age so affects memory loss)

what is nucleotide excision repair repaired by

polymerase delta or epsilon

non homologous end joining (NHEJ)

repairs double stranded breaks

will occur if HDR isnt available

loss of genetic material

what is NHEJs defect

SCID (Severe combined immunodeficiency)