October test Flashcards
what is a zoonatic disease?
a disease that originated in a non-human organism and
“splitover” into humans
How do Viruses replicate?
- Virions enter the host cell
- Reverse Transcriptase will make RNA into DNA
- Integrase splices viral DNA into host DNA
- Transcription/Translation
- New virions bud or burst out
Are viruses considered as a living organism?
Viruses are not really considered to be living organism because
1. They cannon reproduce on their own - they need a host cell
2. They have no energy metabolism
3. No response to stimuli
Only when they enter a host are they considered to be alive.
What are the three orgins of viruses?
Virus First: viruses evolved from complex proteins and nucleic acids before cells did. So viruses contributed to the rise of cellular life.
Reduction hypothesis: viruses were once smaller cells that acted as parasites and larger cells
Escape: viruses evolved from bits of DNA or RNA that escape from genes or larger organisms.
Why is it difficult to treat viruses?
It is hard to treat viruses without hurting the host cell.
Viruses has a rapid rate of mutation (due to reverse transcriptase) so random resistance mutations can occur. Then that resistance baryon will continue to reproduce and increase in frequency. Therefore decreasing the drug effectiveness.
Why are drug cocktails so helpful?
If the virus has the random mutation, using two drugs against it will work better than using just the one
What is reverse transcriptase?
an enzyme found in viruses that is error prone (which is why viruses are prone to mutations).
It mistakes AZT for the Thymidine base pair which is how it killed the virus. The AZT lacks the hydroxyl group in thymidine , therefore nothing else can join it, ending the reverse transcription.
Why is reverse transcriptase prone to so many mutations?
Because it does not have any proof reading capabilities. therefore its unable to go back and fix any mistakes it has made.
this is why many viruses have yearly vaccines. Because the influenza strain changed over time.
What is the theory of natural selection?
Heritable variations passed on selectively leading to a change in genotype of a population.
* A change in your genome that makes you more adaptive to you environment that is passed down to offspring.
what is the theory of evolution?
decent with modification from a common ancestor.
- A change in allele frequency from one generation to another.
- leads to speciation as the genes of each generation will be classified as their own species.
- Variational not Transformational
- often gradual
Proof: homologous structures - similarity suggests a common ancestor.
what is the difference between variational and tranformational?
Transformational - an organism can transform itself and propagate those traits onto future generations
variational - random mutations that occur in a population that increases an organisms fitness (ability to reach a reproductive age and reproduce) over generations.
*random occurrences that are beneficial to that species in its environment.
Which of the following best describes evolution by natural selection?
A. Environmental change causes some individuals to experience mutations. Mutation’s that improve survival or reproduction in the new environment will spread through the population.
B. Mutations are always occurring, regardless of environmental conditions. If a mutation improves survival or reproduction, it will spread through the population.
C. Mutations are alway arising, regardless of the environment conditions. If a mutation is not currently helpful, but is likely to be helpful in the future, it will increase in frequency.
D. Changes in the environment causes individuals to change their phenotype. This change is passed on to the next generation in the form of mutations to their genotype.
Answer: B
What is falsifiability?
- An idea that can never be proven but can but can falsify to support the idea
- what makes the idea scientific is if it can be proven wrong.
When is an idea normally NOT falsifiable?
They are not specific
They are opinions/ subjective
They cannot be measured
Which of the following is not falsifiable?
A. Pacific salmon cannot reproduce more than once in their lifetime.
B. Passenger pigeons never really went extinct: they have just become so rare that they are difficult to find.
Answer: A
what is the value of “n”
One set of an organisms nuclear chromosomes. It also represents the ploidy number. For example, in humans, one set of chromosomes is 23 of them. However humans are diploid, meaning we have two sets of chromosomes. Therefore we have 2n.
What is the value of “C”
The amount of DNA in one set of chromosomes. It should be the same number as the ploidy, and it will double in DNA synthesis as DNA is being replicated. Once the cells have split, it will return to normal. For example in the human cell there is 2C and 4C during division.
NOTE - C is never less then n and is usually a multiple pf n
What is prokaryote cell division
Simple and divide through binary fission
What is Eukaryote cell division
G1 - where the cell grows and prepares itself to divide. (2n&2C)
S Phase (synthesis) - where the DNA is doubled and replicated. DNA is only replicated here!! (2n & 4C until mitosis is complete)
G2 - The cell checks over everything and makes sure its ready for division before M-phase (mitosis)
Mitosis - Where the cell undergoes the process of splitting into two daughter cells
Note: through g1,S and g2 the proteins and molecules are continuously being synthesized in preparation for division and other normal cell functions.
Cells that never divide remain in the g2 stage. Whereas cells that divide rapidly may never enter the g2 stage.
What occurs at the G1 -S Checkpoint?
is the cell in the correct condition to replicate DNA? Is there cell damage? is it receiving signals to replicate?if they fail this checkpoint they will initiate cell arrest or enter g0
What occurs at the G2 Checkpoint?
Is the cell in the right condition to divide? Has DNA full been replicated in the S phase? is any DNA damaged? If at any of the checkpoints there is damage to the cell, it will try and fix itself. However if deemed irreversible, the cell will apoptose
What occurs at the Metaphase Checkpoint
Are the chromosomes ready to separate? Are they ligned up properly? Are they correctly attached to the mitotic spindle? If at any of the checkpoints there is damage to the cell, it will try and fix itself. However if deemed irreversible, the cell will apoptose
What are the stages of Mitosis
Prophase - chromosomes condense and become visible under a microscope. nuclear envelope begins to dissovle and the spindles begin to form.
Prometaphase - nuclear membrane completely dissolves, spindle fibers attach to now visible chromosomes
Metaphase - all chromosomes align along the metaphase plate (aka spindle mid-point)
Anaphase - the cohesion that holds together sister chromatids in the middle of the cell is cleaved and drawn to opposite poles of the cell. Each chromatid is now considered a chromosome (4n&4C)
Telophase & Cytokinesis - chromosomes begin to unfold and a nuclear envelope begins to form while the cell begins to divide into two due to cytokinesis.
Definition of Mitosis
The replication of genetic material. How organelles are replicated and split
