Genetic populations 17/11/22 Flashcards
What is the homo habilis?
-Oldest member of the genus Homo
-Found in East Africa
-Tool user
What is the homo heidelbergensis?
-Big game hunter
-Sophisticated tool user
-Fire user
Where can modern humans be traced back to?
-Modern humans can be traced back to a group of Homo sapiens who lived in Africa 150,000 years ago
-Mitochondrial inheritance down the female
line all came from one ‘mitochondrial eve’
-Y-Chromosome down the male line
-Next-generation sequencing to look at
ancestry
-We are all related to everybody else on the planet
What factors contribute to genetic population differences?
*Mutation
* Recombination and rearrangement
* Genetic drift
* Natural selection
* Bottlenecks and Founder effect
* Admixing and Gene flow
How do mutations cause genetic differences?
-Environmental factors can cause different mutations to occur such as the Chornobyl disaster or atomic bombs in japan
-Epigenetics can also cause differences in gene expression due to environmental factors
What is the probability of mutations occurring?
The probability of a mutation is influenced by the likelihood that the particular error will occur and the likelihood that it will be repaired.
How does recombination and rearrangement cause genetic differences?
-Recombination increases the diversity of a population by changing what genetic variants are inherited together
-Gene dosage can also affect genetics as the gene to metabolize codeine, if you have more genes for that particular function that you will metabolize drugs differently depending on your genetics
How does genetic drift cause genetic differences?
-When a population is separated they will evolve differently from one another based on the environmental factors and genetics within that group
-In small populations, the frequency of a mutation will change randomly and new mutations are likely to be eliminated by chance.
-Fixation is the process by which a new allele replaces the allele that was previously predominant in a population
-The frequency of a neutral mutation largely depends on genetic drift, the strength of which depends on the size of the population
-The frequency of a mutation that affects phenotype will be influenced by negative or positive selection
What are genetic isolates?
Small isolated populations generally show an
increased frequency of rare or population
specific genetic disorders due to increased
mating between close relatives (consanguinity) or among members of the genetic isolate (inbreeding). Monogenic disorders are less likely to show allelic heterogeneity in isolated populations then in more heterogeneous populations. Polygenic disorders are likely to show a reduced number of loci/genes making them easier to study.
What is an example of genetic isolates?
The Bedouin-Arabs of the Negev region of
Israel are a well-studied isolate population.
The population consists of about 90 000
individuals, divided into numerous tribes.
How does natural selection cause genetic differences?
-Whatever increases the chance of survival will be naturally selected
-For example, Kettlewell’s moths. Before the industrial revolution white Kettlewell moths were more common as they were better camouflaged, after the industrial revolution everything was covered in soot and dirt and so the black moths were better suited.
-Another example is sickle cell. Even though this disease is life-threatening, it also protects against malaria and therefore provides some survival increase. This is why sickle cell is most common in areas that are mostly effected by malaria.
What was the Kettlewell moth study?
Hypothesis - more pigmented moths will suffer less predation in areas with high industrial pollution.
Main experiments - a mark–release–recapture experiment that was conducted first in a polluted wood near Birmingham in July 1953. Where moths of both phenotypes were marked and released during the day on specific trees before recapture was attempted over subsequent nights. In 1955 this experiment was repeated on a smaller scale in the same wood and a comparable experiment was carried out in an unpolluted wood in Dorset.
Main findings - recapture always favored the phenotype best camouflaged within that environment, suggesting selective pressure was at play.
Possible issues:
* Moths were released during the daytime. They are nocturnal and don’t fly during the day.
* They do not generally sit around on a tree trunk waiting to be eaten.
* The moths were released at a much high density than is natural.
How does the bottleneck effect cause genetic differences?
-A population bottleneck is an event that drastically reduces the size of a population. The bottleneck may be caused by various events, such as an environmental disaster, the hunting of a species to the point of extinction, or habitat destruction that results in the deaths of organisms.
-Selective bottleneck can occur due to a pandemic, selective because only the more vulnerable may die
-Random bottleneck can occur due to something like a natural disaster where everyone would be affected the same
How does the founder effect cause genetic differences?
-The founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.
-For example, in 1775, a typhoon killed at least 90% of the people on the island of Pingelap in the Western Pacific. One of the 20 survivors carried the mutation for achromatopsia, a very rare recessive eye condition that causes color blindness and extreme sensitivity to light. Now 10% of the population has the condition.
How does admixing and gene flow cause genetic differences?
-Gene flow occurs due to populations mixing. This happens due to wars, slavery, natural disasters, and resources.
-Admixture is when genetics between two different populations combine, for example, spain invading mexico.
