University:
York University
Course:
BIOL 107 | Introduction to Cell Biology
Academic year:

2024
Views:

365

Pages:

2
Author:

Ciara T.

Natural Selection Confer-grant/allow Natural Selection and Populations •Population group of individuals of same species living in same area at the same time •2 conditions for natural selection to occur in population: i) individuals in population vary in characteristics that are heritable (passed on to offspring) ii) in a particular environment, certain versions of these heritable traits help individuals survive better/reproduce more than other versions •if certain heritable traits lead to ↑ success in producing offspring, these traits become more common in the population over time Evolution in Action: Research on Natural Selection •Drug resistance in bacteria Case Study 1: How did Mycobacterium tuberculosis Become Resistant Antibiotics TB: infects lungs, often causing death In late 1980s, rates of TB surged Strains of the bacteria responsible for were resistant to the a global health emergency once-effective antibiotics A Patient History. Diagnosed w/ TB ↳ given antibiotic rifampin Infection cleared after 10 months 2 months later, diagnosed again. •Tests showed the the TB in resistant to rifampin his lungs were completely A Mutation in a Bacterial Gene Confers Resistance DNA from the rifampin-resistant bacteria was found to have a single point mutation in a •rpob codes for gene → гров a component of RNA polymerase (pol) •Rifampin works by binding with the TB w/ transcription RNA pol interfering mutation prevents rifampin from binding Allels That Confer Drug Resistance Increase in Frequency When Drugs are Used •Diagrams show how natural selection acts on individuals (the human), because individuals experience differential success Also shows how only populations (the bacteria) evolve, as alle le frequencies change in populations not individuals Variation existed in the population •both resistant nonresistant strains of TB were present before administration of the drug Variation was heritable •The variation in the phenotypes of the 2 strains was due to variation in? The cells w/ drug resistant alleles had reproductive success seriation Drug Resistance: A Widespread Problem heredity aslaction the •Resistance to a variety of insecticed, fungicides, antibiotics, antiviral drugs, herbicides has evolved in 100's of insects, fungi, bacteria, viruses, plants *As the suseptible individuals die from In every case, evolution has occurred because individuals the drug. resistance allels w/ the hevitable ability to resist some chemical compound ↑ in Arequency were present in the original population Natural Selection Doesn't Change Individuals during the process, individuals do not change - only the - population does For eg: •The frequency of the rifampin-resistant allele↑ the population over time PROCESS: EVOLUTION OF DRUG RESISTANCE M. Jubercules inung 1. Large population of M. tuberculose bachera in patient's args maksum sck A line of the tra happen to have a point mulatory in the pagine sormal грой gere Mutant CT mutation 2. Drug therapy begins killing most tubercus Patient seems cund and drug therapy enosd. Even moiagh the populatio tanatically reclicet a ligh pracottion of the sumasing celly is resutant to the drug 2. The mutant cols preferat. resulting in another major infection of the lungs. The patent Descenes gan 4. A second icurt of drug theran begins but ineffective on the drug resistant techeta The patient dies