Lecture 23 Flashcards
Contrast the multiregional emergence hypothesis and the recent African origin hypothesis
concerning the origins of humanity. What does each hypothesis predict with respect to the fossil
record? Which hypothesis is supported by human mitochondrial DNA? Explain.
MRE: multiregional emergence of humans from home-rectus across the world all at once an hypothesizes that the oldest human fossils should be found at each site of the independent origin
RAO: humanity evolved one time from eastern Africa and migrated out of Africa, hypothesize that the oldest human fossils should be found in Africa
RAO + admi xture with other hominin species is best supported by mitochondrial dna
How similar/different are the genomes of two random humans?
any two random humans differ in 1/1000 bases in term of single nucleotide polymorphism
Where is genetic diversity the highest for human populations? How does this idea tie into the
concept of serial founder effects?
genetic diversity is highest in African populations because as subsets of the African ancestaal populations migrated from Africa serial bottlenecking occurred where gnetic diversity decreased
If we saw an Fst value for comparing populations A and B of 0.65 and an Fst value when
comparing populations A and C of 0.07, how would we interpret this result in terms of genetic
differentiation of these populations?
We would conclude that there is more genetic differentiation between populations A and B compared to between A and C.
if Fst=0 than they are not two distinct populations
Why are phylogenetic trees of human populations misleading? Define reticulation in your answer.
Phylogenetic trees are misleading as they do not consider exchange of genes between the different species populations
Reticulation: is the horizontal mixture of genetic information between populations within a species that violates assumptions of phylogenetic trees.
How do mitochondrial genomes partially circumvent this issue of reticulation?
mitochondrial trees combat reticulation as mitochondrial DNA does not undergo recombination events and is strictly maternally derived.
Define mitochondrial Eve. Does the existence of mitochondrial Eve mean that any other females
that existed concurrently with this individual have no living descendants? Explain your answer.
Mitochondrial eve: a single woman who by which all mitochondrial genes are derived from.
This does not mean other females did not leave descendants, it instead means their mitochondrial DNA eventually went extinct.
How old are the oldest fossils of anatomically modern humans? When did humans and chimps
share a common ancestor?
the oldest fossil of modern humans are 200,00 years old.
Humans and chimps shared common ancester 5-7 million years ago.
shared genomic information amonst great apes
What is a conservative amino acid substitution? Are these expected to be common or rare if most
of the differences between humans and chimps are due to regulatory mutations?
Conservative amino acid substitution is the substitution of an amino acid across species that does not result in any protein expression changes ( similar to codon optimization).
These are expected to be common as they do not have any detrimentla effect.
If you are looking at a particular nucleotide in a gene shared by gorillas, chimps, and humans, and
you see that gorillas and chimps have a G at this position and humans have a T. Which base is likely
the ancestral state? Define outgroup in your answer.
The ancestral state is likely G and humans independently derived the T allele making them an outgroup.
How are we able to determine that humans interbred with Neanderthals and Denisovans?
By sequencing the dna of extracted fossils from denisovans and neanderthals there is evidence of admixture between humans and these other hominin species
What are the three main hypotheses concerning the disappearance of Neanderthals?
- humans drove them to extinciton through violence
- Human drove them to extinction by outcompeting for resources
- Humans were simply more numerous so when admixture occurred the diverged populations were mostly genetically human and had some neanderthal DNA.
- What is adaptive introgression? Provide a potential example of this occurring in humans.
Adaptive introgression is the transfer of genes from one lineage to another as a result of admixture and a subsequent selection of these advantageous alleles in the population that received them.
This occurred in humans. After neanderthals migrated from Africa many years before humans they developed immunity to certain east asian pathogens. When human later migrated to these same regions and admixture happened with neanderthals the advantageous alleles coding for immunity were transferred to humans and over time selected for.
What does FOXP2 tell us about the likely language capacities of Denisovans and Neanderthals?
FOXP2 is a TF that encodes for language and speech abilities so while humans have two structural changes in the amino acid sequences for this gene compared to the great apes
neanderthals and Denisovans share these two structural changes as us which indicates they may have had similar language abilities as us.
What does it mean to “humanize” the FOXP2 allele in mice?
In a study, the alle for the FOXP2 gene in mice was mutated to be more similar to humans. This helped the mice to learn to escape a maze faster and cuased changes in their vocalization
What are two population genetic consequences of adaptive alleles spreading in a population?
When adaptive sales spread in a population :
- there could be a subsequent increase in variants that are linked to the adaptive alleles
- at that locus on the chromosome there will be a decrease in variation
Did lactose tolerance arise once or multiple times independently? Defend your answer
Lactose tolerance arose independently in different populations as each population developed different mutations that elicited the same effect of lactase persistence. Considering these populations either relied on cattle or were pastoralists they evolved to have these mutations.
Contrast convergent and parallel evolution.
convergent evolution is the independent development of different mutations across populations
parallel evolution is the independent development of the same mutations across populations.
What is the main benefit of darker skin in equatorial environments?
The increased melanin in darker skin provides protect from UV rays that are in higher abundance near the equator
What is the main potential drawback of darker skin at higher latitudes?
Darker skin at higher latitudes has a draw back as increased melanin where there are low UV levels hinders the harvesting of that UV to make vitamin d3.
What are the three main applications of forensic genetics?
- linking Crime Scene DNA to a suspect
- paternity testing
- identification of remains
What are three criteria for a locus to be included in CODIS?
- known chromosome locations and assorrt indepenndetly ( if they did not two markers would hav eoverlapping information)
- must have multiple alleles of at most 25% frequency ( if it were greater, many people would be hojmozygous for the allel and it would not be informative of the indentiyof the individual)
- consistent and reproducible PCR
Consult table E.2 in the slides and the book and calculate the probability that a random individual
would have the following genotype assuming HWE
Homozygous for FGA= P^2=(.18*.18)=
Heterozygous for vWA= 2pq=(2.017.125)=
Heterozygous for D3S1358= 2pq(2.186.088)=
joint probability= .0324.00425 0.032736= 0.0000450774
Consult table E4 and identify each CODIS marker that excludes F2 from being the father of the
child.
FGA: the 23 allele is maternally derived so the child 20 allele must have come from the father however f2 is heterozygous for 18 and 23 therefore it could not have been the father as it cannot pass down the 20 allele
vWA: child has 17,18 allele and because mother has 18,18 had to have gotten 17 allele from father
D8S1179: child has two 14 alles so father must have an 14 allele like the mother but he doestn
D16S539: child received 12 allele from mother so father must have 14 allele but he doesn’t
D21S11: child received 30 allele from mother as she does not have 28 allele. 28 allele has to have come from father however F2 does not have 28 allele.
