Chapter 14 Eukaryotic DNA replication Flashcards
The larger size and complex packaging of eukaryotic chromosomes means they must be replicated from
from multiple origins of replication
–It is a complex of both an RNA polymerase and a DNA polymerase
–Makes short RNA primers that are then extended with DNA to produce the final primer
Eukaryotic Primase
Eukaryotic Primase
–It is a complex of both an RNA polymerase and a DNA polymerase
–Makes short RNA primers that are then extended with DNA to produce the final primer
Which strand is DNA polymerase epsilon found on?
Leading Strand
Which strand is DNA polymerase alpha and DNA polymerase delta found on?
lagging strand
A significant problem must be resolved in linear chromosome replication!! What is it?
removal of the last primer on the 3’ end of lagging strand
leaves a gap that cannot be primed and With each round of DNA replication, the linear eukaryotic chromosome becomes shorter.
Solves this problem: With each round of DNA replication, the linear eukaryotic chromosome becomes shorter
Telomeres
Telomere sequence
5’ TTAGGG 3‘:
is an enzyme that forms the telomeres on the 3’ end of DNA strands eukaryotic chromosomes.
Telomerase
Where does telomerase remain active?
Embryonic stem cells
What gives cancer cells the characteristic of immorality?
ability to activate telomerase
What do humans and other primates have in common?
Chromosome 2 in humans have a random telomere sequence in the middle which matches up with 2 different chimpanzee chromosomes
Rate of DNA damage
•DNA damage occurs at a rate of 1,000 to 1,000,000 molecular lesions per cell per day!!
Person who recognized that base excision repair constantly counteracts the collapse of our DNA
Tomas Lindahl
Person who worked on mismatch pair and recognized how the cell corrects errors that occur when DNA is replicated during cell division
Paul Modrich
Person who worked on nucleotide excision repair and recognized the mechanism that cells use to repair UN damage to DNA
Asis Sancar
DNA repair mechanisms that able to repair many different kinds of DNA damage
non-specific
•corrects damaged or mismatched nitrogenous bases
excision repair
Example of nonspecific repair
excision repair
DNA repair mechanisms that –targeting a particular type of DNA damage caused by UV light called thymine dimers
Specific
DNA damage caused by UV light
thymine dimers
A stretch of DNA that codes for a type of protein that has a function in the organism
gene
