Lecture 13 Flashcards
Australopithecus
- 2-4 MYA (S. Africa)
- bipedal, not a tree dweller
- several species
- flat skull bases
- stood 4’-5’ tall
- human like teeth
- brain size of a gorilla’s (small)
- hunter-gatherer lifestyle
A. afarensis
“Lucy”
-3.6 MYA
Larger brain, more human like skull, less prominent face
Homo habilis
- 3 MYA
- humanlike cave-dweller
- cared intensely for young
- first to use tools extensively (habilis means handy)
- coexisted with and was followed by homo erectus
Homo erectus
1 MYA
- shallow forehead, massive brow ridges, brain about 1/3 the size of modern humans
- angled skull-base, possible speech
- social, cooperative, used fire
- male-female pairs
- found in China, Java, Africa, Europe, and SE Asia
- Pockets may have persisted until about 35,000 years ago
When did homo sapiens first appear?
“The wise human” probably fist appeared about 200,000 years ago
Homo sapiens idaltu
- lived about 156,000 years ago
- physically similar to modern humans
- probably resembled an Australian aborigine
Homo neanderthalensis
- Split from the human lineage about 516,000 years ago
- Lived all over Europe
- Larger brains, prominent brow arches, muscular jaws, distinct spacing of teeth, and large barred-shaped chest
when did Neanderthals disappear?
by 28,000 years ago
Otzi, the ice man
a peserved man, frozen in ice from about 5,200 years ago, died about 3300 BC
- it was found in the Schnalstal glacial in 1991
- genetically similar to modern soutjer European populations of Sicily and Sardinia
Neanderthals revisted
- They had variants of the FOXP2 gene (possible speech)
- Some had mutations in the MC1R gene (had pale skin and red hair)
Denisovans
Nuclear sequences suggest Denisovans separated from Homo sapiens and Neanderthal about 1 million years ago.
-Remains found in a cave in Sivera and probably once widespread in east Asia.
Mitochondrial DNA (mtDNA)
- used to trace maternal lineage
- lack of DNA repair in mitochondria leads to a faster mutation rate
Y chromosome
- sons inherit it form their fathers
- used to trace male lineage
Mitochondrial “Eve”
mtDNA sequences of indigenous peoples worldwide were compared to determine the common ancestral mtDNA sequenced
Hypothetically, when and where did ancestral woman live? Who also lived around this time?
~170,000-200,000 years ago in Africa.
-This is remarkably close to the date of the homo sapiens idaltu fossils (~156,000)
What supports the Out of Africa hypothesis
mtDNA
Y chromosome
autosome sequences
Hypothesis 1 of expansion of modern humans from Africa to the rest of the world
- Out of Africa or replacement hypothesis
- Within Africa, Homo sapiens evolved from Homo erectus.
- descendents migrated from Africa about 60,000 years ago to replace hominids living in Europe, Asia and Middle East
Hypothesis 2 of expansion of modern humans from Africa to the rest of the world
- Multiregional hypothesis
- Homo ererctus migrated out of Africa to Europe, Asia, and Middle East
- Evolution of homo sapiens occured in multiple locations with interbreeding between populations
Distinctive genetic nametag that Native Americans carry
5 mtDNA and two Y chromosome haplogroups
what is a mutation and where does it occur
a mutation is a change in a DNA sequence and occurs at the DNA or chromosome level
Polymorphism
a genetic change that is present in > 1% of a population
The effects of mutations
loss-of-function
gain-of-function
“loss-of-function” mutations
recessive
“gain-of-function” mutations
dominant
germline mutations
- originate in meiosis
- affect all cells of an individual
somatic mutations
- originate in mitosis
- affect only cells that descend from changed cell
Examples of mutations that cause disease
beta globin gene
collagen genes
What agent causes a mutation and how does it occur?
agent = mutagen
-occur spontaneously or by exposure to a chemical or radiation
Spontaneous mutation
- de novo or new mutation
- not caused by exposure to known mutagen
- result from errors in DNA replication
- DNA bases have slight chemical instability
what alternating forms do spontaneous mutation exist in?
tautomers
-as replication form encounters unstable tautomers, mispairing can occur
Does the larger or smaller genes have higher mutation rates?
larger genes
-but each human gene has about 1/100,000 chance of mutatng
why do mitochondrian genes mutate at a higher rate than nuclear genes
becaust mtDNA cannot repair their DNA
How can estimates of mutation rate be derived?
from observation of new dominant alleles
-for autosomal dominant genes, mutation rate - # of new cases.2X where X - # of individuals examined
