Ch. 8b Extrachromosomal Replicons (Exam 2) Flashcards
What happens to the ends of linear DNA molecules after successive rounds of replication?
Shortening
Where is the natural position for the priming site of the lagging strand?
Near the replication fork
Why isn’t the extreme 3’ end of the lagging strand always copied?
Because primers are only placed at the replication fork, which does not exist until helicase starts unwinding the parent strands. Ergo, the 3’ tip of the lagging strand isn’t formed
What happens to the 3’ end of the lagging strand when a true 3’ end doesn’t form?
There is a missing Okazaki fragment, which causes the lagging strand to be shorter than it should be
What are telomeres?
DNA sequences made up of multiple copies of short repeats, or satellites
What is the function of telomerase?
They extend telomeric DNA at the 3’ overhang to reverse the loss of DNA from the lagging strand’s missing 3’ end Okazaki fragment
What is telomerase made of?
RNA and protein
What is unusual about telomerase (HINT: use of RNA and protein)?
Because the RNA is used as a template for 3’ extension, and the protein synthesizes DNA via reverse transcriptase
What happens after the protein component of telomerase synthesizes enough DNA?
Polymerase primes and synthesizes a new Okazaki fragment from the telomerase’s 3’ extension, forming a complete double strand
How does mitochondrial replication fit into the cell cycle (HINT: describe as flowchart in 4 steps)?
DNA replication > DNA segregation > mitochondrial duplication > mitochondrial/organelle segregation
What is meant when we say that mitochondrial replication appears to be stochastic?
Each copy is randomly redistributed
What is the overall result of such random distribution of mitochondria?
Some mitochondrial DNA molecules are replicated more times than others
What is the protein involved in the formation of the membranous vesicles in animal mitochondria?
Dynamin
In mitochondrial DNA (mtDNA) replication, the number of genomes increases in proportion to the…
Mitochondrial mass
Does each mitochondrial genome replicate the same number of times after each replication?
No
Since each genome replicates a variable number of times, it leads to changes in…
Allelic representation in the daughter mitochondria
What does the “D” in the term “D-loop” stand for?
Displacement
What is a D-loop?
Non-coding region that acts as a promoter of the heavy and light strands
What does the RNA primer do in the first step of D-loop replication?
It initiates replication at the origin of the H strand
What happens after the primer initiates replication at the H strand in the second step of D-loop replication?
DNA is synthesized from the primer to form a new L strand, and a D-loop is created, which displaces the original L strand
In the third step of D-loop replication, after the D-loop displaces the original L strand, what happens?
Replication of the new L strand continues 2/3 of the way around the H strand until it passes the origin of the old L strand
In D-loop replication, what is prompted after the new L strand passes over the old L strand’s origin?
Synthesis of the new H strand
Nearing the end of D-loop replication, the completion of the new L strand prompts this action.
The release of daughter genomes
At the end of D-loop replication, why does the daughter genome with the new L strand seal itself quicker than the daughter with the new H strand?
Synthesis of the new H strand began when the new L strand was already 2/3 of the way sealed, so the new L strand ended up completing first
