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BIOL001 Evolution and HIV
Terms in this set (63)
Change in the distribution of heritable phenotypes
Changes in the distribution of heritable phenotypes in a population
Group of the same species living in the same area that can mate with each other
Requirements of evolutionary change
-heritable variation in the phenotypes of individuals due to genetic variation
-a force (mechanism) of change
Can individuals evolve?
No, only populations because genotype doesn't change after birth
Can evolution purposefully generate variation?
No, acts on existing variation or variation that arises by random mutations
Can evolutionary change lead to organisms that are perfectly suited for their environment?
No because environmental conditions change, traits have trade offs, and they are constrained (limited to existing of randomly introduced variation)
Source of new alleles, rarely (if ever) cause significant changes in allele frequencies
Change due to random sampling of population (alleles)
-chance events can cause allele frequencies to change unpredictably
-dramatic reduction in population size due to random events
Examples of genetic drift
Natural disaster, disease, random fertilization
Change due to movement between population
Change due to differences in survival and reproduction (unequal fitness)
Change due to human intervention (humans choose which individuals mate based on their traits)
change due to differences in mate preferences
How many factors is random sampling due to?
Is random fertilization always occurring?
When are allele frequencies more stable from generation to generation?
When the population size is larger
T/F: microevolution can increase the frequencies of alleles that reduce an individuals ability to survive and reproduce (gene flow, genetic drift, mutation, artificial selection)
T/F: a population can undergo rapid microevolutionary change (gene flow, genetic drift)
T/F: microevolutionary change can introduce new alleles into the population (gene flow, mutations)
T/F: population can be affected by multiple mechanisms of microevolution at the same time
T/F: genetic drift can significantly decrease genetic variation in a small population
Are all populations influenced by genetic drift via random mating at all times?
T/F: allele frequencies of small populations are more likely to be significantly altered
Loss of significant portion due to random events
-allele frequency changed, genetic diversity is reduced (fewer different alleles)
New population established by small group
How many of the initial alleles are present in the "new" population?
Only a portion of initial population's alleles are present (virtually always less genetic variation)
What is likely to happen due to small population size?
Additional change via random fertilization
Factors that magnitude of change depend on (gene flow)
-differences in allele frequencies of the 2 populations
-how many move and in what directions
-duration of movement (ex. long term vs. short term)
Correct term for "survival of the fittest"
Survival of the gene most likely to reproduce
Measure of how many alleles an individual contributes to future generations (can lead to adaptations)
Heritable traits that increase an individual's relative fitness
Number of alleles an individual is able to pass on in relation to others in the population
Can adaptations change?
Yes, whether a trait is considered an adaptation or not can change with evolutionary changes (ex. light fur is not an adaptation in a dark environment)
Favors one extreme
Disfavors both extremes
Favors both extremes
2 common forms of sexual selection
Competition and mate choice
What traits does sexual selection favor
Traits that improve chances of mating (may often decrease ability to survive)
Where is sexual selection observed?
Species where male and females differ in their traits
Is genetic modification artificial selection?
Does artificial selection lead to adaptions?
No because it doesn't have a goal
-human preference determines which alleles are passes onto next generation
Individual virus (AKA virus particle)
Do viruses have to enter a cell?
Yes, they must enter a cell to reproduce (requires host cell's energy, resources, and machinery)
Morphology of most viruses
-genetic information in center (DNA or RNA)
-protein shell (capsid)
Human immunodeficiency virus
-single stranded RNA genome
How are different proteins formed in HIV?
mRNAs produced by expression of a gene can be spliced differently (also occurs in eukaryotic cells)
HIV life cycle
1. attachment and entry
3. reverse transcription (copying the HIV RNA genome into DNA)
4. integration (insertion of HIV DNA genome into chromosome
5. transcription and translation of viral genes
6. production of new viral genomes
7. assembly of new virions
8. exit (AKA budding)
What type of cells do HIV affect?
T-cells (must have the membrane protein CD4)
HIV attachment and entry steps
1. HIV envelope protein interacts with CD4; envelope protein changes shape
2. Interaction with CD4 allows HIV envelope protein to interact with CCR5 coreceptor
3. HIV envelope protein inserts into cell membrane
4. HIV envelope and cell membrane fuse
5. Fusion allows HIV capsid to enter the cell
Using an RNA template to form a complimentary DNA strand
Are there any cellular (host) enzymes that can copy the HIV RNA genome to make a complimentary DNA strand?
Insertion of double-stranded HIV DNA into one of the host cells chromosomes (location is random)
HIV enzyme that inserts DNA genome into host cell's chromosomes
-allows HIV genes to be expressed using host cells enzymes and resources
-explains why HIV is essentially incurable (passed on when cell divides)
How fast does HIV replicate?
Rapidly, about 2 days
Is reverse transcription accurate?
No, increased chance of mutations. HIV replicates rapidly so the frequency of a particular mutation can increase quickly
What nucleotide is AZT similar to?
T, but has 3 nitrogen atoms instead of a hydroxyl group (-OH)
Steps of drugs that inhibit HIV enzyme (less likely to affect normal cellular processes and prevent HIV from reproducing)
-reverse transcriptase interacts with AZT and adds to the DNA strand
-addition of AZT prevents addition of more nucleotides
-replication of HIV genome stops and new viruses cannot be produced
Can mutations that allow drug resistance be present before someone starts taking the drug?
Yes, they can be
What mechanisms of evolution can alter the frequency of an AZT resistant mutation prior to AZT treatment?
Gene flow, genetic drift, and natural selection
Highly active antiretroviral therapy
-combination of 3 different drugs
-typically inhibits at least 2 different HIV enzymes
What do individuals that lack CCR5 receptor have?
They are homozygous for a specific mutation in the CCR5 gene (CCR5Δ32)
Is the CCR5Δ32 mutation old or young?
-limited gene flow
THIS SET IS OFTEN IN FOLDERS WITH...
BIOL001 DNA Information Processing
BIOL001 Cell Division and Inheritance
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