BIO4 - Evolution and Ecology Flashcards
How do viruses require extensions of the central dogma of molecular biology?
Viruses require extensions of the central dogma of molecular biology because they can contain different types of genetic material (DNA or RNA) and rely entirely on the host cell’s machinery to reproduce. They often deviate from the traditional DNA → RNA → protein flow by hijacking the host’s systems for their replication. Some viruses, like retroviruses, use reverse transcription (RNA → DNA), which extends the central dogma to include pathways not typically seen in cellular (Eukaryote) organisms.
What is the difference between the lytic and lysogenic cycles of viruses?
Lytic and lytogenic viruses are two distinctly different approaches of virus reproduction.
Lytic cycle: in the lytic cycle, the virus injects its genetic material into the host-cell and immediately hijacks its machinery to create new virus particles. Eventually, the host-cell will burst (lyse) leading to a rapid spread of the virus within the affected organism.
Lysogenic cycle: In the lysogenic cycle, the virus does not immediately take over the hos-cells machinery to replicate. Instead, it incorporates its genome into the host cell’s DNA and is replicated each time the cell divides. The virus can then remain dormant for long periods of time, until it is triggered, and enters the lytic cycle.
What characterizes a retrovirus?
Retroviruses are viruses that inject their genetic material into the host cell in the form of RNA. They then use reverse transcription (RNA -> DNA) with the help of the enzyme reverse transcriptase. After reverse transcription the virus DNA can then be incorporated into the host cell’s DNA, and either enter the lytic or lysogenic cycle.
HIV is an example of a retrovirus.
How can sequence (protein, RNA) alignments be used to construct phylogenetic
trees?
When you compare the sequence of aminoacids between species, you see that species that are more similar have a more similar genome. Therefore, you can compare their protein / RNA sequences, to determine how closely related two organisms are.
What is the evidence that all life on earth descends from a common ancestor, LUCA?
It is the Last Universal Common Ancestor, where you can trace the development of species back to the same single living cell. Many of the biological pathways and molecules are identical (or almost identical) for all living organisms, which strongly suggests that we share a common ancestor.
What are the conditions for evolution in biology?
First and foremost, evolution takes place because of random mutations in the genome of biological organism. These mutations create different phenotypes in individuals, which in turn makes an organism more or less competitive (i.e. survival of the fittest).
This assumes finite ressources, which the organisms compete for. Better adapted organisms win the battle of these resources, and therefore, create offspring with similar genome.
What is an allele? What is the gene pool?
Alleles are different variants of a gene. Diploid cells contain two alleles of each gene, which can be the same or different. Different organisms of a population can have different combinations of alleles, leading to a natural diversity in the population.
Alleles can be recessive or dominant, depending on whether they define the phenotype of the organism that carries them. Sometimes one allele is defective, which is mostly recessive. Two such alleles together can lead to genetic disease.
The gene pool of a population consists of all the allele’s present in a given population.
How can genetic diversity in a population of organisms be increased?
Genetic diversity in a population is mainly increased by mutation, sexual reproduction (meiosis), and environmental changes that create selection pressure.
What are examples of mutagens?
Mutagens are compounds that are known to increase the mutation rate in living organisms. Examples of such compounds include:
Radiation and certain chemical agents such as benzene.
How can mutations lead to changes in gene expression?
First of all, it is important to understand the different types of mutations.
Deletions: The deletion of a nucleotide in the genome
Insertions: The insertion of a nucleotide in the genome
“Swap”: One nucleotide is changed with another in the genome.
Deletion and insertions lead to what is called a fremshift mutation. I.e. since the genetic code is read 3 basepairs at a time, if you add or subtract a base, it will change the way the sequence is read.
Swapping a nucleotide can either lead to a missense or nonsense mutation. Missense is when the gene is expressed with a different amino acid, nonsense is when the nucleotide swapped results in a stop codon. Some of these mutations can be silent, which means that the nucleotide that is swapped, does not change the aa-chain.
Why can gene duplication be useful for evolution?
Having a “spare” gene, means that you can have changes happen to one gene without it affecting the phenotype. This mutated spare can then contribute to evolution. This is how hemoglobin was created from myoglobin.
- What is horizontal gene transfer?
What is a genome-wide association study?
A Genome-Wide Association Study (GWAS) is a research approach used to identify genetic variants associated with specific traits or diseases. It involves scanning the genomes of many individuals to find common genetic markers (such as single nucleotide polymorphisms, or SNPs) that occur more frequently in people with a particular trait or condition compared to those without it. GWAS helps researchers understand the genetic basis of complex traits and diseases.
What is adaptive laboratory evolution and what is it useful for?
Adaptive Laboratory Evolution (ALE) is a method used to study evolution in controlled environments. In ALE, microorganisms are exposed to specific selective pressures (such as changes in temperature, pH, or the presence of certain chemicals) over many generations. The organisms evolve to adapt to these conditions, and researchers track genetic changes and improved fitness over time.
Useful for:
Understanding evolutionary processes and genetic adaptations.
Engineering microorganisms for industrial applications, such as improving resistance to stress or enhancing production of biofuels and pharmaceuticals.
Studying antibiotic resistance and microbial pathogenesis.
What is convergent evolution?
Convergent evolution is the process where unrelated or distantly related organisms independently evolve similar traits or adaptations in response to similar environmental pressures or challenges. Despite having different evolutionary origins, these species develop analogous structures or functions to solve similar problems.
An example is the evolution of wings in birds, bats, and insects. Though these species are not closely related, they all developed wings for flight.
How have humans shaped the biomass distribution on earth since their appearance?
Humans and domesticated mammals now far outweigh wild mammals (not animals). I.e. associating oneself with humans seems to have been a successful strategy for many species.
