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Which bacteria are used for conjugation?
Via an interrupted mating experiment
Hfr + F- cell (with several mutations)
Explain the interrupted mating experiment.
The Hfr and F- cells are mixed together and then samples are remvoed from the culture at various times and plated on different agar dishes lacking a variety of things
What did the experiment show?
it showed that all genes being transferred are not at once, but rather occur at different times.
What might be the problem with mapping genes via conjugation?
It is not completely accurate and is unable to distinguish the relative positions of two genes less than two minutes apart
Explain the activity of telomerase.
What does this mean for cells?
it is not active in all mammalian cells. It is functinal in the early embryo, but after birth, it is only active in stem cells.
it means that they shorten at every division
What is the senscent state?
after 50 rounds or so of division, the cells enter a senescent state in whcih they remain alive but cannot divide.
It is a protective mechanism that counters the tendency fo a cell lineage to accumulate defects such as broken or rearranged chromosomes. It prevents cells from becoming cancerous by ensuring that the lineage is terminated before the danger point is reached
True or False: All somatic cell lines display senescence.
Defend your answer.
False: Not all display senescence
Cancerous cells divide continuously in culture, their immortality being looked on as analogous to tumor growth. They may activate telomerase
What is a future experiment for teloerrase.
Observation: It is not clear whether telomerase activation is a cause or an effect of cancer, although the former seems more ikely because dyskeratosis congenita results from a mutation in the gene specifying the RNA component of human telomerase
There are little to no therapeutic relevancies with this
Currently, the protein component is used to make vacines. And, the RNA component is thought to be able to inhibit the telomerase enzyme if it is complementary
What do cyclins influence?
DNA replication by regulating events at the replication origin
Where can DNA damage take effect?
At the G1 to S phase transition: it can affect both the G1/S-Cdk, which will in turn affect the S-Cdk since it will not be able to accumulate and allow transition
S phase, which may cause a shunt of the pathway into apoptosis, slowing down, or stopping.
M-phase: affects the M-CDK, which allows the G2 phase transition to M phase
dual role of CENPA
located in metaphase chromosome
- CENP-A makes chromosome more rigid
- CENP-A also forms the platform for kinetochore assembly
a set of genes and other DNA sequences that enable plasmids to capture genes from phages and other plasmids
What are the three bacteriophage types?
icosahedral: individual protein subunits (protomers( arranged in 20 faced geometric structure that surrounds nucleic acid
filamentous: protomers arranged in helix
head-and-tail: combine both features
Most eukaryotes follow only the __, but few of them __
lytic infection cycle
take over the host cell's machinery in a way that the lytic bacteriophage takes over a host bacterium
The progeny of a eukaryotic virus miight be ...
- a) stored in the host cell prior to release, forming a crystalline inclusion inside the cell
- b) continually extruded from the infected cell; the virus particles become coated with a small part of the outer cell membrane as they are released from the cell
a type of viral retroelement encapsidted genome is made of DNA
acute transforming viruses
retroviruses that cause cell transformation because of abnormalities int heir genome structures; they carry cellular genes that they have captured from previous cells they have infected
explain defective retroviruses
if a cellular gene replaces part of the retroviral gene complement, the virus can't replicate and produce new viruses, as it has lost genes coding for vital replication enzymes and/or capsid proteins
These defective retroviruses are not always inactive as they make use of proteins provided by other retroviruses in the same cell
diference between retroviral synthesis and retrotransposition
retroviral: not only is it an outside thing, but it gets immediately converted into DNA and then dsDNA--> reintegratin
retrotransposition: RNA--> dsDNA--> reintegration; it is also endogenous
an active or inactive retroviral genome integrated into a host chromosome
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