lec 16- The history in our genes Flashcards
MHC (major histocompatibility complex) genes have hundreds of alleles that control what?
immunity responses to antigens by linking T cells
do most genes have more than 2 alternate alleles?
yes
breast cancer gene (BRCA1) also has many alleles, how large is the gene?
120,000 base pairs
what does BRCA1 normally act as and what happens when mutated?
acts as a tumor repressor, but when mutated it will increase breast cancer risk
what is coalescence?
when alleles in a population can be traced back in time to a single common ancestor
How was the breast cancer gene activated?
from one point mutation (G to T) many generations ago
what thing do gene locations on chromosomes have?
their own genealogy (gene trees)
is it possible to produce a consistent genealogy that agrees with a phylogenic tree based on morphilogical traits?
yes
how do companies like 23andMe trace backwards to find out your ethnic backgrounds?
by tracing the history of many allele variants or mutations (called markers) to reconstruct the history
what is very common in building a phylogeny with genetic data?
homoplasy because only four nucleotides to study in DNA sequences that make it common
what are slowly evolving conserved genes useful for in the phylogeny?
distantly related species
what are rapidly evolving genes useful for in the phylogeny?
closely related lineages
who is mitochondria inherited from, and does the DNA undergo crossing over?
inherited from mother, DNA does not undergo crossing over
what is the shape of the Mitochondria’s DNA?
a loop (like ancestral bacteria) that has 37 functional metabolic genes except in control region
why is brown fat darker than normal fat?
because it is densely packed with mitochondria, which makes the fat warmer than normal due to respiration and high heat production
is brown fat that is used in hibernation an ancient survival adaptation?
yes
what are the four common methods in molecular phylogenetic analysis and tree building?
-Maximum Parsimony: simplest explanation favored
-Distance Matrix (neighbor joining): cluster taxa based on genetic distance (more different = more distant)
-Maximum Likelihood: finds most likely tree given specific model of molecular evolution
-Bayesian methods: looks at probability that a tree is correct given a specific model of molecular evolution
what do humans have an identical Beta-globin protein with?
chimpanzees
are phylogenetic trees hypotheses?
yes, they are constantly reevaluated when new data becomes available
what are the two hypotheses behind human evolution?
-humans evolved from widespread species connected by gene flow and interbreeding
-humans evolved from a single African human ancestor
who tested the blood DNA of modern africans to see if they had the highest genetic diversity (meaning it’s the origin of human evolution)?
Sarah Tishkoff
which hypotheses of human evolution was supported?
-second, Africans displayed the most genetic variation (mutations) of mtDNA then rest of the world
what is mtDNA (microsatellite DNA)?
non-coding repeating short sequences, high mutation rates
did race evolve first in Africa?
no, physical characteristics like braincase, protruding chin and more evolved first in africa, while race evolved later
where did neanderthals originate from?
eurasia
when did neanderthals live?
in Europe and the near east from 200,000 to 28,000 years ago
what were the characteristics of neanderthals?
stocky,strong, and thick boned with large brains (larger than modern humans)
did neanderthals and humans interbreed?
yes
what are the two main ideas behind the extinction of the neanderthals?
- ice age, harsh temperatures and altered vegetation and animal distribution
- competition from modern humans who left Africa around 60,000 years ago (most likely)
what is HIV and AIDS?
-HIV: human immunodeficiency virus, two main types HIV-1 and HIV-2, with HIV-1 responsible for most infections in four main strains, both are retroviruses (RNA viruses)
-AIDS: acquired immunodeficiency syndrome, is a medical condition that develops at the advanced stage of HIV infection, first diagnosed in 1981
where did HIV-1 originate?
africa
where did HIV-1 come from?
from chimps and gorillas that carry a similar virus known as the simian immunodeficiency virus (SIV), humans ate Bush Meat (chimps and gorillas) and SIV jumped to humans
what are the four strains of the HIV-1 virus and where did they come from?
O and P- came from gorilla strains of SIV, and later transferred to chimps then humans
M and N- evolved independently in humans, from two contact events with chimps
