Mid Term Flashcards
What characteristics do viruses have that consider them to be alive
Contain nucleic acid, replicate, and can evolve rapidly by natural selection
What charcteristics of viruses consider them to not be alive
Viruses do not have a metabolic system, and cannot reproduce on their own, they must invade a host cell to do so
What are the basic features of viruses
How do viruses replicate
Virus RNA infects cell, reverse transcription occurs and virus genome is replicated into DNA , virus gene is transcribed into RNA, virus RNA is translated into protein and new viruses are produced
Evolutionary origins of HIV
AZT is used to treat HIV, it binds to reverse transcriptase and stops the replication of HIV, however reverse transcriptse went through a mutation which gave it the proof reading ability so it is able to detect AZT and remove it
Why is it difficult to erradicate viral diseases
Because they have high mutation rates and are always evolving, it is diffucult to create a vaccine that accounts for all variants
How did HIV become drug resistant
HIV developed a mutation that is resistant to AZT (random), this mutation was favored by the environment (natural selection) so it reproduced more
Why will the effectiveness of ant-viral deug treatment decrease over time
HIV has a high mutation rate, because of this there are many variants and variants that are resistant to the drugs can be a result of this
Principles underlying evolution by natural selection:
mutations in the population are random, these mutations create genetic variation, the variants that are more likely to survive reproduce more resulting in a change of the genotype of the population
Why are multiple drugs used to treat HIV
Multiple drugs target different areas of the HIV life cycle, making it harder for the virus to evolve
What is a scientific theory
A coherent set of testable hypotheses that attempt to explain facts about the natural world
What is a belief system?
A set of beliefs which together form the basis of a religion, moral code, or philosophy
-does not rely on evidence
What evidence supports evolution
biogeography, comparative morphology, geology, fossils
Biogeography
Similar species are fiund in distant places-a common ancestor changed over time into different forms
Comparative morphology
when compared bone structure of different species are similar-com from one common ancestor
Vestigal structures
Structures that aren’t useful
Geology
Geological change is slow, this is evidence that earth is billions of years old-plenty of time for evolutionary change
Fossils
Many forms of life existed then but have since gone extinct, evidence that life is different from the pasr
Darwins contribution to theory of evolution
There is variation for traits in a population, individuals whose traits allow them to better survive and leave more offspring are favoured, overtime individuals with thesw traits become more common
Evolution is variational
individual vary in their traits this is passed on, individuals cannot change and then pass on these characteristics
What are some misconceptions about the theory of evolution
Evolution does not occur gradually, selection is targeted to a specific goal, evolution results in organisms perfectly suited for their environment, the fittest indivuals are the fastest, strongest, and largest
Where is DNA located in prokaryotic cells
DNA is packaged into a singular circular chromosome located in a central region called the nucleoid
Where is DNA located in eukaryotic cells
The nucleus
Phases of cell cycle of prokaryotic cells
DNA replication,
Phases of cell cycle of eukaryotic cells
Stages of mitosis
Stages of meiosis
DNA recombination in prophase of meiosis
Randomness of alignment of homologous pairs in metaphase I
Distance between genes and recombination
Cell cycle phases
G1, S, G2, Mitosis
What occurs during G1
cell growth before DNA replicates
What occurs during S phase
DNA replicates and chromosomal proteins are duplicated
G2
After DNA is replicated the cell prepares for division
Why do cells divide
When a cell grows the volume becomes greater than the surface area, the plasma membrane is responsible for all cell mechanisms, the surface area must keep up with the volume of cell for it to get all the proper nutrients at one point the surface area cannot keep up
Cell cycle checkpoint 1
between G1 and S, checkpoint proteins make sure no mutations are present
Cell cycle checkpoint 2
right before mitosis, makes sure there were no errors in synthesis, if there were the errors are corrected, if the errors cannot be corrected, apoptosis occurs
Cell cycle checkpoint 3
Between metaphase and anaphase, makes sure spindles are attached properly so chromatids can be pulled apart properly
What is positive regulation
pushes cell cycle to go
What is negative regulation
Inhibits cell cycle
Process of positive regulation
Cyclin and CDK bind together, Cyclin-CDK complex becomes phosphorylated, the complex phosphorylates the target protein, the target protein is now active and moves cell into next stage of the cell cycle
Process of negative regulation
p53 detects DNA damage and increases p21 expression by binding to the promoter, p21 binds to Cyclin-CDK and inactivates it, the complex cannot phosphorylate target proteins
What is the risk of any protein involved at the cell cycle checkpoints not functioning properly (be specific)?
developmental defects, cancer
Why is p53 considered to be the guardian of the genome
p53 detects damages in the cell and repairs them, if p53 cannot repair it triggers apoptosis.
What risks are associated with p53
If p53 is mutated it cannot stop the cell cycle, the cell cycle will continue to divide uncontrollably. This could lead to cancer
Prophase
centrosome divides into two parts and move to opposite ends of cell, begins to develop spindles and nucleus begins to shrink
Metaphase
chromosomes align themselves in the middle
Anaphase
Chromatids begin to seperate to opposite ends (spindles pull them apart)
Telophase
Chromatins unfold and spindles disassembles, return to interphase
Interphase
Regular growth period, where the cell spends most of its life cycle
What does mitosis ensure in future generations
Future generations are identical (genetic composition and identical chromosome set)
When would cells be programmed to die by apoptosis
If DNA damage cannot be repaired
Aneuplody
uneven distribution of chromosomes
Difference between meiosis and mitosis
Mitosis-genetically identical, 1 division, 2 daughter cells, diploid no recombination
Meiosis- genetically distinct gametes, 2 cell divisions, 4 daughter cells, haploid, recombination
Why is meiosis I reductional
A haploid is produced from diploid-the number of chromosomes decreases
Why is meioisis II equational
The number of chromosomes stay the same
Characteristics of homologous chromosomes
Same structural features, the same genes at same loci positions (one from mom one from dad)
Mechanism of recombination
Homologous chromosomes pair, they arrange themselves on top of each other, homologous chromatids crossover and exchange segments (genetic material changes), the pair seperates at first meiotic division
Mechanism by which recombination creates novel combinations of alleles
Every chromosome undergoes at least one recombination, new combinations of alleles are created
Linked genes
If genes are close to each other they are more likely to be inherited together, crossover is more likely to occur where there is more space
What are mechanisms that give rise to variation in meiosis
Independant assortment, random fertilization
Independant assortment
alleles of two or more diffrent genes get sorted into gametes independantly of one another
Random fertilization
any ranom combination of sperm and egg cell
Mechanisms giving rise to aneuploid products of meiosis
non-disjunction (unequal distribution)
Relationship between age of an oocyte and the risk of offspring having Down Syndrome
The older the oocyte the higher chance of down syndrome
Animal life cycle
meiois to form gametes, gametes are fertilized to create a zygote, zygote undergoes mitosis
Plant and fungi life cycle
meiois to form spore, spore undergoes mitosis to form gametophyte, gametophyte undrgos mitosis to form gamete, gamete fertilized to form zygote, zygote undergoes mitosis to form sporophyte
Life cycle of fungi and algae
meiois to form spore, spore undergoes mitosis to form gametophyte, gametophyte undergoes mitosis to form gametes, gametes fertilized to form zygote
Purines
Adenine, Guanine
Pyrimidine
Cytosine, Uracil, Thymine
Direction of movement of DNA polymerase on template strands
3’-5’
Meaning of semi-conservative, leading strand and lagging strand
Each DNA double helix acts as a template for synthesis of new strand
3’ vs 5’ polarity of nucleic acid chains involved in DNA replication
Direction of elongation of a given DNA strand
5’-3’
Main features of chromosome anatomy
chromatids, centromeres
what is n
number of unique nuclear chromosomes present in an organism (coefficient tells us the number of unique sets)
What is c
Amount of DNA in one genome (coeeficient tells us the number of copies of the entire genome)
How does coefficient of n change throughout cell cycle
Stays the same
How does coeeficient of c change throughout cell cycle
doubles at s phase and goes back after m
C-value paradox
genome does not dictate complexity
Structures of DNA
mechanism Structures that ensure inheritance of sameness
Structure of replication bubble
cell senescence
why chromosome shorten at replication
telomerase action
