Replications + Mutations in DNA

initiation

initiation

the DNA double helix “unwinds” (or denatures)

DNA helicase

an enzyme that “unzips” the DNA by acting as a wedge to drive it apart

replication fork

a point at which a DNA molecule is replicating

ATP hydrolysis

ATP is broken down and releases energy which is used by cells to perform various functions

topoisomerase

breaks the sugar-phosphate backbone of DNA, allowing the strands of DNA to untwist, then reforming it

goal of DNA replication

to generate two daughter molecules from each parent DNA molecule

primer

a strand of nucleic acid that is necessary to begin synthesis of a new DNA strand (usually RNA)

primase

an RNA enzyme that starts the synthesis of an RNA primer, using a DNA template

polymerase

an enzyme that synthesizes nucleic acid polymers

elongation

synthesize a new strand of DNA

leading strand

synthesized continuously

lagging strand

synthesized discontinuously; has multiple RNA primers

Okazaki fragment

newly formed DNA making up the lagging strand in replication

DNA ligase

links together Okazaki fragments together to give a continuous strand and unites broken DNA strands

telomeres

repeated DNA sequences at the ends of eukaryotic chromosomes, allows chromosomes to be extended at the ends + triggers repair pathways

incorporation error rate

the probability that an incorrect base will be inserted into a new strand during DNA replication

proofreading

DNA polymerase excises a base that is incorrectly inserted according to the template

mismatch repair

a mechanism that scans DNA after it has been replicated and corrects any mismatches

base-pair substitutions

a change of a single base pair in a nucleotide sequence

point mutation

a mutation that results from the gain, loss, or substitution of a single nucleotide

spontaneous mutations

a genetic change caused by internal cellular mechanisms (errors in DNA replication)

mutagens

any agent that increases mutation rate

induced mutations

changes in the sequence of DNA caused by a mutagen

excision repair proteins

Definition:

recognize the distortions in the DNA helix, excise incorrect segments, and facilitate the synthesis of the correct DNA sequence

silent mutations

a change in the gene sequence that has no effect on the amino acid sequencing

loss-of-function mutations

results in the loss of a functional protein

gain of function mutations

results in a protein with a new function

conditional mutations

a mutation that results in a characteristic phenotype under certain conditions environmentally

deletions

a mutation resulting from the loss of a continuous segment of a gene or chromosome

duplications

mutation in which a segment of a chromosome is duplicated

inversions

a rare 180 reversal of the order of genes within a segment of a chromosome

translocations

segments of chromosomes break off and become joined to different chromosomes

nonhomologous end joining

a repair pathway that functions to join together the two ends of a broken chromosome