Module 2 Termination & Repair

In prokaryotes, replication is complete when _____ after replicating their portion of the circular DNA In eukaryotes, many _____ fuse to become larger until it reaches the ends of the chromosomes the ____

Chromosomal end must be repaired. The enzyme ____ prevents shortening of lagging strands during replication. It is an RNA-directed DNA polymerase, or in other words a _____ A protein component is _____, an enzyme that can make DNA copies from RNA templates

The ends remain unpaired as there is no place for a primer to be made. They get shorter with every division. The end of linear chromosomes are _____, which protect the genes from getting deleted. _____ six base pair sequence repeated 100 to 1000 times

Telomerase is active in ____ and ____ but not in ____ _____ received the Nobel Prize for _____

Telomerase-deficient mice had (4)

Fidelity of DNA replication is due to three activities: Accurate selection of ____ Immediate _____ _____ repair

There are _____ genes whose products participate in DNA repair. Fialure to repair DNA leads to a _____

Types of DNA Damage or lesion 1) _____ The loss of an amino group. Like a C converted to a U 2) ______ of the normal bases because of failure to proofread. Like U instead of T 3) ____. Which could be single ____ or _____ The frequent cause is ____ and ____ 4)____ can be formed between bases. Chemotherapeutic drugs can crosslink DNA. Either same strand _____ or opposite strand _____

Other lesions: _____ Removal of purines by acid and heat; removal of altered bases by DNA glycolysis _____ ionizing radiation, alkylating agents _____ proofreading of incorrectly incorporated bases ____ Intercalating agents cause addition or loss of nucleotide _____ Cyclotubyl dimers resulting from UV irradiation _____ Breakage of phosphodiester bonds by ionizing radiation ot chemicals _____ covalent linkage of two strands by alkylating agents ______ Disruption of structure by free radicals

Agents that damage DNA: Certain wavelengths of ____: - Ionizing like _____ and ___ - longer-wavelength ____ (260 nm) Highly-reactive ____ produced during cellular respiration Chemicals in the environment like _____ in cigarette smole Also chemicals used in _____

Types of DNA DAMAGE: ______ A) UV light induces formation of pyrimidine dimers and joined by cyclobutane ring B) Alkylation or addition of methyl or ethly groups C) Carcinogens add bulky chemical groups

Types of DNA DAMAGE: ______ A) deamination of bases b) depurination (loss) resulting to a cleavage

Mechanisms of DNA repair: General classes: ______ chemical reation responsible for DNA damage ______ removal of damaged bases and synthesis of replacement

Three types of excision repair: ______ cause:_____ uses:_____,____ DNA repair mechanism that corrects damaged or altered bases by excising the specific damaged base, using specific glycosylases. The gap is then filled with the correct nucleotide sequence by the action of DNA polymerase and ligase, restoring the integrity of the DNA.

Three types of excision repair: ______ cause: ______ uses: ______ addresses a wider range of DNA damage, including bulky lesions and thymine dimers. a stretch of nucleotides containing the damaged site is excised, and the gap is filled in through the action of DNA polymerase and ligase, ensuring the removal and repair of a larger segment of damaged DNA.

Three types of excision repair: ______ cause: ______ uses: _____ designed to correct errors that occur during DNA replication, such as mismatched base pairs. MMR proteins identify and remove the mismatched bases, and the correct bases are then inserted.

Last mode of repair: ______ Causes: _____ _____ two broken ends of a chromosome are glued together, not accurate _____ matches info from a homologous chromosome that matches the damaged one. Template usage.