The progression of cells through the division cycle is regulated
by extracellular signals from the environment, as well as by internal signals
that monitor and coordinate the various processes that take place during different cell cycle phases.
How replication in eukaryotes is regulated as once per cycle?
Eukaryotic DNA replication is regulated
to ensure all chromosomes replicate once and only once per cell cycle
. Replication begins at many origins scattered along each chromosome. Except for budding yeast, origins are not defined DNA sequences and probably are inherited by epigenetic mechanisms.
How the cell cycle is regulated quizlet?
The cell cycle is regulated
to ensure cells only divide as and when required
. At each checkpoint in the cell cycle, a set of conditions determines whether or not the cell will continue into the next phase. Cyclins and CDK’s are molecules that check the cell cycle at various points.
Why does the cell cycle need to be regulated?
Cell cycle regulation is
crucial for proper cellular homeostasis
. Communication between or within a cell is done through cell signaling and a change in the activity of the cell is sent as a signal that may trigger a cascade of reaction for the body to respond accordingly.
How does the cell ensure that DNA is replicated once and only once per cell cycle?
During successive cell division cycles, identical genetic information must be precisely transmitted from the mother cell to the two daughter cells. This is achieved by
duplicating the cell’s genomic DNA in S-phase and distributing the two copies equally to the daughter cells at M-phase
.
Which does DNA polymerization by DNA polymerase require?
New DNA is made by enzymes called DNA polymerases, which require
a template and a primer (starter)
and synthesize DNA in the 5′ to 3′ direction.
What mechanism do Eukaryotic cells employ to keep their chromosomes from replicating more than once per cell cycle?
The molecular mechanism that restricts DNA replication to once per cell cycle involves
the action of a family of proteins (called MCM proteins) that bind to replication origins together with the origin replication complex (ORC) proteins
(see Figure 5.17).
What is cell cycle and how is it controlled?
Positive Regulation of the Cell Cycle
Two groups of proteins, called cyclins and cyclin-dependent kinases (Cdks), are responsible for the progress of the cell through the various checkpoints
. The levels of the four cyclin proteins fluctuate throughout the cell cycle in a predictable pattern (Figure 2).
Why is regulation of the cell cycle important quizlet?
Why is regulation of the cell cycle important?
Internal regulators allow the cell cycle to proceed only when certain processes have happened inside the cell
Cancer cells do not respond to the signals that regulate the growth of most cells.
How do cells regulate themselves?
The cell replicates itself in an organized, step-by-step fashion known as the cell cycle
. Tight regulation of this process ensures that a dividing cell’s DNA is copied properly, any errors in the DNA are repaired, and each daughter cell receives a full set of chromosomes.
How does replication licensing ensure that DNA is replicated only once at each origin per eukaryotic cell cycle?
How does replication licensing ensure that DNA is replicated only once at each origin per eukaryotic cell cycle? –
a replication licensing factor binds to the origin during G1 phase and is removed during S phase
. In what ways is eukaryotic replication different from bacterial replication?
Why do eukaryotic cells have multiple origins of replication?
Prokaryotic chromosomes have one origin of replication, while eukaryotic chromosomes have multiple origins. This is because
eukaryotic chromosomes are much larger, so multiple origins are needed to replicate the entire chromosome in a short amount of time
.
What controls the process of DNA replication?
DNA replication is controlled by
the replisomes
which are found in the chromosomes. The replisomes are what replicate the DNA from the origins in the chromosome.
Do eukaryotes have Okazaki fragments?
Okazaki fragments are present in both prokaryotes and eukaryotes
. DNA molecules in eukaryotes differ from the circular molecules of prokaryotes in that they are larger and usually have multiple origins of replication.
How many DNA polymerases are in eukaryotes?
Eukaryotic cells contain
five
DNA polymerases: α, β, γ, δ, and ε. Polymerase γ is located in mitochondria and is responsible for replication of mitochondrial DNA.
How do the DNA polymerases of eukaryotes differ from those of prokaryotes?
Both eukaryotic and prokaryotic DNA polymerases build off RNA primers made by primase.
Eukaryotic DNA replication requires multiple replication forks, while prokaryotic replication uses a single origin to rapidly replicate the entire genome
. DNA replication always occurs in the nucleus.
What is the process of DNA replication in eukaryotes?
DNA replication in eukaryotes occurs in three stages:
initiation, elongation, and termination
, which are aided by several enzymes.
How are eukaryotic chromosomes replicated?
As in prokaryotes, the linear chromosomes of eukaryotes replicate
by strand separation and complementary base pairing of free deoxyribonucleotides with those on each parent DNA strand
. As with prokaryotes, DNA replication in eukaryotic cells is bidirectional.
Where does replication occur in eukaryotic cells?
| Prokaryotic DNA Replication Eukaryotic DNA replication | Occurs inside the cytoplasm Occurs inside the nucleus | Only one origin of replication per molecule of DNA Have many origins of replication in each chromosome |
|---|
What are two things that control the cell cycle?
Two groups of proteins, called
cyclins and cyclin-dependent kinases (Cdks)
, are responsible for the progress of the cell through the various checkpoints.
