Why circular chromosomes do not have telomeres?
Most prokaryotes with circular genome do not have telomeres. During DNA replication, the leading strand of circular chromosomes can simply continue to grow from 5'→3' direction until its 3' end is joined to the 5' end of the lagging strand coming around from other direction.
Is telomerase used in circular chromosomes?
In wild-type cells that contain multiple chromosomes, it is rare to find fused or circular chromosomes, even when the activity of telomerase has been compromised: this is because cells can extend and maintain telomeres by using a mechanism called homology-directed recombination that repairs double stranded breaks in …
Why do prokaryotes not need telomerase enzymes?
Bacteria don't need telomerase because their chromosomes don't have telomeres. Most bacterial chromosomes are circular, meaning they have no end.
Why do somatic cells not have telomerase?
Telomerase activity is absent in most normal human somatic cells because of the lack of expression of TERT; TERC is usually present.
Why is telomerase used by some eukaryotic cells but not prokaryotic cells?
Telomeres are only present in eukaryotes. This is the case because eukaryotes are the only type of cell that contains linear DNA. There are telomeres on each end of the chromosomes within the nucleus of these cells. Prokaryotes on the other hand have a single circular strand of DNA within a nucleoid.
Do all chromosomes have telomeres?
So the telomeres are special DNA that sit at the end of the chromosome that have repetitive sequences that are recognized as the end of the chromosome, but they keep the chromosome from becoming frazzled or damaged. And every time the cell divides, the telomeres also divide. But sometimes they can become shorter.
What problem with replication of linear chromosomes does telomerase address?
What problem with replication of linear chromosomes does telomerase address? The lagging strand stops short of the 3' end during replication, so chromosomes would shorten in each replication cycle without telomerase.
Why are telomeres not important to bacterial cells?
Bacteria don't need telomerase because their chromosomes don't have telomeres. Most bacterial chromosomes are circular meaning they have no end.
Why are bacteria not dependent on telomerase for complete DNA replication?
Why are bacteria not dependent on telomerase for complete DNA replication? Telomerase allows for the accurate replication of linear DNA molecules, and bacteria have circular chromosomes. Compare and contrast DNA replication in prokaryotes and eukaryotes. Eukaryotic DNA replication is very similar to that in E.
What cells do not have telomerase?
Telomerase is found in fetal tissues, adult germ cells, and also tumor cells. Telomerase activity is regulated during development and has a very low, almost undetectable activity in somatic (body) cells. Because these somatic cells do not regularly use telomerase, they age. The result of aging cells is an aging body.
What the consequence is for a eukaryotic cell that lacks telomerase?
Answer and Explanation: A eukaryotic cell lacking telomerase would shorten the ends of its chromosomes with every replication.
Why do eukaryotes need telomerase?
To prevent the loss of genes as chromosome ends wear down, the tips of eukaryotic chromosomes have specialized DNA “caps” called telomeres.
What would happen to chromosome ends in the absence of telomerase?
These results demonstrated that telomere loss in telomerase-deficient cells lacking cell cycle regulation results in chromosome rearrangements leading to cancer.
How does telomerase prevent linear chromosomes from shortening during replication?
Explain how telomerase prevents linear chromosomes from shortening during replication. Telomerase binds to the overhang at the end of a chromosome. Once bound, it begins catalyzing the addition of deoxyribonucleotides to the overhang in the 5' -> 3' direction, lengthening the overhang.
Why are bacteria not dependent on telomerase for complete DNA replication quizlet?
Why are bacteria not dependent on telomerase for complete DNA replication? Telomerase allows for the accurate replication of linear DNA molecules, and bacteria have circular chromosomes.
What happens to cells without telomerase?
Since in a healthy person only certain kinds of cells have telomerase turned on, this means that as people get older and their cells have divided many times, their telomeres get shorter and shorter. Eventually they lose too many repeats and their cells die.
What happens when telomerase is absent?
In the absence of telomerase, telomeres progressively shorten with every round of DNA replication, leading to replicative senescence.
Why is telomerase needed in eukaryotes but not prokaryotes?
Telomeres are only present in eukaryotes. This is the case because eukaryotes are the only type of cell that contains linear DNA. There are telomeres on each end of the chromosomes within the nucleus of these cells. Prokaryotes on the other hand have a single circular strand of DNA within a nucleoid.
Why telomeres are needed in eukaryotes but not prokaryotes?
We just saw that prokaryotes have a round or circle shaped chromosome so there is no end for prokaryotic chromosomes to be identified. In the case of eukaryotes, They have a linear or straight chromosome in which the end or the final part is identifiable. This is why telomeres are present only in eukaryotes.
What happens if the telomeres are removed?
However, each time a cell divides, some of the telomere is lost (usually 25-200 base pairs per division). When the telomere becomes too short, the chromosome reaches a "critical length" and can no longer replicate. This means that a cell becomes "old" and dies by a process called apoptosis.
Are bacteria Dependant on telomerase to complete synthesis of their chromosome ends?
Telomerase is an RNA-containing enzyme that adds telomeric DNA sequences onto the ends of linear chromosomes. Bacteria are dependent on telomerase to complete synthesis of their chromosome ends.
Why is telomerase needed?
Telomeres act as protective caps on the ends of our chromosomes and prevent damage and fusion with other chromosomes. A useful analogy for this can be the way an aglet of a shoelace prevents fraying, unravelling and tangling of laces.
Why do eukaryotic chromosomes have telomeres?
Telomeres are the physical ends of eukaryotic chromosomes. They protect chromosome ends from DNA degradation, recombination, and DNA end fusions, and they are important for nuclear architecture. Telomeres provide a mechanism for their replication by semiconservative DNA replication and length maintenance by telomerase.
Why do eukaryotic cells require telomerase?
Telomeres are needed to maintain the ends of chromosomes and sustain chromosome stability in eukaryotic cells. Telomeres loss their noncoding DNA sequences in the erosion that happens during DNA replication in each cell cycle. They do this to protect the genetic information in the chromosomes (42, 43).