Unit 7 Lesson 6: Evolution of the Influenza Virus Flashcards
(26 cards)
genetic drift
variation in the frequency of genes in a population due to random chance events, such as natural disasters or disease
In an ecosystem, genetic drift is the change in the frequency of genes in a population due to chance. What happens to alleles during genetic drift
During genetic drift, certain the presence of certain alleles can increase or decrease in frequency. This change is not dependent on which genes are better suited for survival, it is random.
There are many reasons genetic drift can occur, including
individuals being left behind, immigration, and natural disasters.
natural selection vs genetic drift
In comparison, natural selection is not random. Natural selection is a process in which those that are better suited to their environment will survive and reproduce.
Natural selection leads to a population dominated by organisms that are
anatomically, behaviorally, and physiologically well-suited to survive and reproduce in a specific environment.
Example of genetic drfit
For example, a beetle population consists of four green and two red beetles that live on a specific tree. During a thunderstorm, high winds happen to blow away the red beetles, leaving only the green ones. This random event has changed the frequency of color in this population of beetles.
There are four parts to the process of natural selection:
- There is the potential for a species to increase in number. Overpopulation may occur where there are many organisms born and not enough resources for the population.
- There are differences in the population because of genetic variation of individuals due to mutation and sexual reproduction.
- Those born that have the ability to compete for the environment’s limited supply of resources are more likely to survive and reproduce.
- Those organisms that are better able to survive and reproduce in that environment will pass along their genetic information to the next generation.
Influenza
Influenza is a viral infection that affects the respiratory system in humans and many other animals. T\
influenza virus and vaccines
Furthermore, because of the time it takes to mass produce a vaccine, scientists involved in the production of flu vaccine must make predictions about which flu strains will be the most infectious during flu season and make the vaccine against those strains. Sometimes, those predictions hold true and the vaccine is very effective against the flu virus for that year, but other times, different flu strains become more infectious and the flu vaccine is not 100% effective against the flu virus for that year.
The influenza virus, like most viruses, mutates, or undergoes genetic change, in response to its environment. There are slight genetic changes in the virus, but it is still the influenza virus. What effect does this have
. When the virus mutates, a person’s antibodies no longer recognize it to fight off the infection. Through the process of natural selection, the virus has adapted to the point where it is no longer recognized by the antibodies. This allows the virus to survive, reproduce, and be transmitted to other people.
The influenza virus has one of the highest mutation rates among viruses, which creates an enormous diversity in flu viruses every year.
This is why flu vaccines must be administered to people every year. The vaccine from the previous year is not effective against the current flu viruses.
Another example that shows natural selection is the ability to tolerate lactose, a sugar that is present in milk. What do lactoase intolerant people not have
People who are lactose intolerant do not have the enzyme to break down lactose in milk and dairy products.
In ancient times, the ability to digest milk disappeared in childhood, and today only about 40% of humans have this ability. The majority of adult humans who can digest milk have ancestors that once lived in Europe, Turkey, and certain parts of Africa. Why can these people drink milk while others cant
Thousands of years ago, people in these areas raised cattle and goats as a source of food. The milk of the cattle and goats is nutritious, and the ability to digest the milk into adulthood would give people a survival advantage. This would also increase their fitness and allow them to reproduce.
genw that allowsone to digest peope
The ability to digest milk comes from a gene that has undergone a mutation and is found on one of the non-sex chromosomes, or autosomes. Male and females can both pass this mutation equally since it is not sex-linked.
how to be lactose intolherant
A person who is not lactose intolerant inherited two copies of this gene, one from the mother and one from the father.
Another example of the process of natural selection can be found with bacteria.
There are more and more case studies of antibiotic-resistant bacteria as a consequence of natural selection. Bacteria grow and multiply quickly, copying their DNA each time they divide. This can lead to mutations, and some of the mutations can give the bacteria a survival advantage. These mutations can make some bacteria resistant to antibiotics or other antibacterial products. The bacteria that are not resistant will die, leaving the resistant bacteria to reproduce. In such a case, the bacteria have adapted to their environment through the process of natural selection.
Describe how the influenza virus adapts to its environment.
The influenza virus mutates enough to have changes in its genetic makeup but still remains the virus. This prevents human antibodies from recognizing the virus, allowing the virus the chance to reproduce and spread to others.
How is the ability to digest milk as an adult an adaptation as a result of natural selection?
Some people in certain areas of the world who lived thousands of years ago raised cattle and goats and relied on their milk as a source of nourishment. Those who could digest that milk had a mutation in their DNA that allowed them to tolerate lactose. They survived and thrived in their environment and were able to pass that ability through their genetic material to future generations.
lactose intolerance is due to the inability to digest an enzyme found in milk. This is incorrect.
. It is rather the lack of the enzyme that breaks down the sugar lactose that causes lactose intolerance and results in the inability to properly digest lactose. The video goes on to state that this enzyme is called lactose. This is also incorrect. The enzyme that breaks down lactose is known as lactase, and this enzyme breaks down the sugar lactose. Finally, the video states that two copies of the dominant allele are needed to be able to digest lactose. However, because this is a dominant gene, only one copy would be needed, either from the mother OR the father, for a person to be able to digest lactose. Two copies of a recessive gene are required for lactose intolerance.
How is the ability to drink milk into adulthood a beneficial trait?
It is a beneficial trait because those who have the trait are better able to survive in their environment and have more children, but it is only beneficial if a significant portion of your nutrition comes from milk or other dairy products
The surface of the virus contains two proteins—hemagglutinin, or HA, and neuraminidase, or NA, what do they do
—hemagglutinin, or HA, and neuraminidase, or NA—that activate the body’s immune system to protect against the virus.
Small changes in the influenza virus can occur such that the immune system cannot recognize HA or NA. This is called antigenic drift
a natural process seen in viruses in which mutations caused by the process of viral replication cause the virus to appear differently to the immune system
The infection begins when the influenza virus has entered into a few cells. The viruses use the cells to replicate the virus’s genetic information and create new viruses, which then leave the cells to infect other cells. Some of the copies are exact copies of the virus, and some contain mutations due to antigenic drift. Soon, billions of cells are infected, and that is when most people start to feel sick, although everyone responds differently.
In order to discover why there is such a variety of responses in humans to the influenza virus, Bloom and his team infected cells made from lung tissue in a petri dish and used sophisticated techniques to look at the messenger RNA (both cellular and viral) of single cells. To determine if a cell had recognized the virus, they measured the amount of interferon, which is a particle that activates antiviral defenses in the body. They also measured the amount of viral mRNA to determine the success of the virus in each cell, while locating mutations as the virus moved from cell to cell. They discovered that cells with the unmutated virus contained more mRNA. Cells that contained the mutated virus had the opposite effect. Based on their findings, they concluded tha
viral replication depends on cells being infected with working viral genes. Mutated viral genes cannot replicate the virus correctly.
