9.3 Evolution's Role in Medicine and Agriculture Flashcards
Studying the ______ of disease can help us understand and control disease ________.
evolution; frequencies
Lack of ______ can make crops and livestock ________ to evolutionary forces.
variation; vulnerable
Micro-organisms reproduce very ______ (some as little as 20 mins)
Therefore, Microevolution can happen extremely
______
quickly; fast
Bacteria and viruses need to be monitored in order to prevent _____________________________
disease outbreaks and pandemics
Advances in genetics allows for the study of alleles and how they play in both _____________
causing and preventing diseases
Pandemic definition
A disease outbreak over a large geographical area
Alleles and Disease Resistance
Some humans/populations show resistance to certain diseases due to natural selection
For example:
-Europeans with CCR5 D32 allele resistant to plague; now resistant to other diseases like HIV
Africans with SCA allele resistant to malaria
-Europeans heterozygous for CF allele resistant to bacterial infections (TB, typhoid fever, salmonella, cholera)
Influencing Disease Frequencies
Some diseases may not be selected against due to age of onset or medical interventions
-Huntington’s Disease– adult onset (~40); people have often already reproduced
-Cystic fibrosis – better treatment/management allows affected individuals to survive and potentially reproduce
-Tests for many genetic diseases – can choose to reproduce or not
Evolution in Agriculture
Agricultural developments aim to produce as much food as possible
Pesticide resistance and reduced genetic variability are problems that have been encountered
Slowing Pesticide Resistance
-New pesticides expensive to develop; only effective for a short period of time
-Refugia: local environments not affected by regional ecological change
For example:
-Most of field sprayed with pesticides, allows some resistant pests to survive
-Part of field not sprayed with pesticides, allows resistant and sensitive species to survive and reproduce
-Therefore, keeps allele frequency lower
Refugia definition
local environments not affected by regional ecological change
Genetic Diversity in Crops
-Crops are Artificially Selected to have certain traits
-Easy to grow; clones have reduce genetic variability
-E.g. Irish potato famine (1840s) – only one type of potato planted, completely wiped out by blight
-Corn in US (1970) – fungus
-California vineyards (1980s) – insect pests
Genetic Diversity in Livestock
-Artificial selection reduces variability in animals as well as plants
-Chickens bred for egg-laying ability need to be cross-bred with other breeds to increase diversity in case of disease outbreaks
-Reproductive technologies like artificial insemination allow for desired traits to be passed on more quickly, but further reduce variation
-However, can allow for breeding that wouldn’t happen in nature (due to location/distance)
how does artificial insemination affect diversity?
reduces genetic variation
Why are new flu vaccinations needed every year?
the virus mutates so quickly, every year new vaccines have to be created to protect against the new strains
Why are Europeans more likely to be resistant
to HIV than Asians or Africans?
-people of European descent carry at least one copy of the D32 allele of the CCR5 gene
-this allele allowed some people to resist plague infections in the past and they were more likely to survive
Why do heritable adult-onset diseases such
as Huntington’s disease still occur in the
population?
-in adult-onset genetic diseases, symptoms may occur AFTER reproduction has already taken place. -therefore, the disease-causing allele may have already been passed on to the offspring
How does the occurrence of one disease affect
the incidence of another? Provide an example
-20 percent of Europeans and people of European descent have been found to carry at least one copy of the D32 allele of the CCR5 gene
-Scientists think this allele allowed some people to resist plague infections in the past and they were more likely to survive.
-So individuals with the allele were selected for whenever there was an outbreak of the plague
How can refugia help reduce pesticide
resistance?
both pesticide-resistant and pesticide-sensitive insects survive in the refuge and they will interbreed.
If the allele for pesticide resistance is recessive,
only about a quarter of the offspring will be resistant.
Thus, over several generations, the proportion of pesticide-resistant insects in the population
will be significantly reduced
refugia
Refugia are any local environments that have not been affected by regional ecological change.
In agriculture, refugia are blocks of land in fields that are not sprayed with pesticides
Identify two alleles that cause disease yet have
been favoured by natural selection. Explain
why they were favoured
Cystic Fibrosis allele
-evidence shows that heterozygous individuals may be resistant to several serious diseases caused by bacteria, including tuberculosis, typhoid fever, salmonella poisoning, and cholera
D32 allele
-scientists think this allele allowed some people to resist plague infections in the past and they were more likely to survive. So individuals with the allele were selected for whenever there was an outbreak of the plague
Provide an example of how artificial
insemination has affected livestock
Using this technique, a single prized male can produce far more offspring than he would have through conventional selective breeding.
Though the desired traits are maintained in the population, the genetic diversity within the breed is reduced, since so many individuals have the same father
How have outbreaks of diseases such as cholera
affected humans over time?
Cholera was once extremely common in Europe.
Before the invention of antibiotics, those who got cholera had a 50 percent chance of dying from it
It greatly reduced population sizes
How have reproductive technologies such
as genetic screening affected the evolution
of diseases?
Tests have been developed for many genetic diseases, including Huntington’s.
People who discover they have a disease-causing allele may choose not to reproduce.
If they do not reproduce, the frequency of the allele in the gene pool will be reduced
Suppose herbicide has been developed that
attacks only purple loosestrife. Create a plan
to slow herbicide resistance in these plants,
which have invaded a large marsh
-create a refuge so that both pesticide-resistant and pesticide-sensitive insects survive in the refuge
and they will interbreed.
If the allele for pesticide resistance is recessive,
only about a quarter of the offspring will be resistant.
Thus, over several generations, the proportion of pesticide-resistant insects in the population will be significantly reduced
How have modern agricultural practices made
crops vulnerable to evolutionary forces?
Some agricultural practices also reduce the genetic diversity of livestock and crop species, which can leave them vulnerable to evolutionary forces
-e.g. monoculture
Pregnant women often experience nausea,
especially in the first three months of fetal
development. The nausea is often triggered by
certain types of food, including spices. Form a
hypothesis about how this nausea might be an
evolutionary adaptation
-morning sickness protects the embryo by causing pregnant women to physically expel and avoid foods that contain chemicals, especially toxic chemicals in strong-tasting vegetables, caffeinated beverages and alcohol
-this helps the fetus become less vulnerable to the effects of chemical disruptions
Some people believe that because a new
influenza vaccine is needed each year, there
is no point in getting vaccinated.
(a) Discuss some of the disadvantages in getting
vaccinated each year.
Some vaccines are associated with fever, rash, and achiness. Serious side effects are rare, but may include seizure or life-threatening allergic reaction.
Some people believe that because a new
influenza vaccine is needed each year, there
is no point in getting vaccinated.
(b) Why should governments keep investing
money to develop a new flu vaccine each
year?
Because the virus mutates so quickly, every year new vaccines have to be created to protect against the new strains
Some individuals who are infected with
malaria develop anemia, which is a deficiency
of red blood cells.
(a) How could anemia benefit these
individuals?
people with sickle cell anemia are resistant to malaria
Some individuals who are infected with
malaria develop anemia, which is a deficiency
of red blood cells.
(b) If these individuals then have children,
will the children be anemic? Explain.
since anemia is a recessive disorder, at least one parent has to carry 2 recessive alleles and the second parent must be heterozygous for the children to be anemic
Which population of pigs is more vulnerable to
disease? The genetically identical population or the genetically diverse population? Explain
the genetically identical population is more vulnerable to disease
-without genetic variation, a population cannot evolve in response to changing environmental variables or diseases and, as a result, may face an increased risk of extinction
-the greater the variation in genes, the more likely it is that individuals in a population will possess the differentiated genes which are needed to adapt to an environment
Scientists have to monitor disease-causing bacteria and viruses because of their ability to _____ quickly
mutate
An allele that, when present in both copies, leads to a deadly disease in which sufferers die before they can have children. When present in heterozygous form, however, the allele imparts resistance to many serious diseases caused by bacteria, including cholera. Cholera was very prevalent in ancient Europe, and now one in every 25 people of European descent carry this allele. Which genetic disease is this?
cystic fibrosis
An allele that, when present in both copies, leads to a deadly disease in which sufferers die before they can have children, but when present in heterozygous form imparts resistance to many serious diseases caused by bacteria. The survival benefits of this disease allele…
allow the allele to be maintained in the gene pool.
What genetically linked disease is most likely to decrease in frequency over time?
a) Childhood disease with treatments available
b) Childhood-onset disease with no treatments developed
b) Childhood-onset disease with no treatments developed
A childhood-onset disease will result in a phenotype of the disease, and likely an individual with compromised health or reproductive abilities. If there are no treatments, the disease will run its course, and it is likely the alleles for the disease will not get passed on to any offspring. Treatable diseases may boost the organism’s health enough to reproduce as well.
In the 1340s, Europe suffered from a widespread outbreak of a deadly disease caused by a bacterium. It killed about one-third of Europe’s population. Which disease caused this pandemic?
bubonic plague also known as the black death
The white leghorn is the breed most widely used for producing eggs. What is a disadvantage of selectively breeding a chicken to maximize egg production?
It is more susceptible to disease
