A gene is a part of a chromosome. Genes are in pairs
Genes affect our learning ability
A chromosome consists of a double-stranded chemical = DNA
Each pair (23 in humans) splits apart taking its genes with it
Sometimes can get the genes from the other chromosome by a process called `crossing over’
Natural selection is not good or bad.
It just happens.
Most of the mutations that occur are deleterious.
Evolution of traits
Natural selection (Natura)
There was probably one ancestor from one place- Africa.
All modern people can trace their heritage to Africa.
DNA samples of 12,127 men from 163 Asian and Oceanic populations.
Every one of the subjects carried a mutation at one of 3 genetic markers on the Y Chromosome.
Those three sites can be traced back to a single African population some 35,000 to 89,000 years ago.
Although there was probably one population, several species of early man may have appeared and died out.
Somewhere between 200,000-500,000 years ago some migrated out of Africa (Lemonick, 1994; Harris and Hey, 1999).
All children from the same mother have identical mitochrondrial DNA
Africa has been shown to be the actual birthplace of Eve at 200,000 years ago on the basis of mtDNA (Cann, Stoneking, and Wilson)
mtDNA change only by mutation (1-2% every 100,000 years).
Each chance mutation is preserved in the next generation
50 genes =cognitive differences between man and ape.
Just 50 out of 140,000 genes that humans and chimps are thought to possess ( 0.3%) may account for all of the cognitive differences between man and ape.
Chimps and gorilla are more closely related to humans than they are to orangutans (Jean-Jacques Hublin)
Humans = a third race of chimpanzees.
From our DNA , humans appear from a genetic perspective as a third race of chimpanzees.
Although chimps took a different evolutionary path from humans about 8 (9?)? million years ago, they share 98.4 percent of our DNA.
In comparison, on the average humans share 99.8 percent of the same genetic material (Lewontin, 1972).
There are Learning and memory genes
during learning (STM) and memory (LTM) new genes are expressed that are required to establish long-term memories.
There are specific genes devoted to memory storage.
most identified as affecting memory are involved in signal-transduction pathways for purposes unrelated to memory
Evolution of Gene Related to Brain's Growth
Genes affect the evolution of the cortex.
A gene (ASPM) helps determine the size of the human brain.
ASPM has been under intense Darwinian pressure in the last few million years,
changed its structure 15 times since humans and chimps separated from their common ancestor.
Formation of memories
If neuron fires often and strongly it is declaring that this is an event that should be recorded and the relevant genes turn on.
The synapses holding STM are made by proteins and become tatooed into LTM.
LTM (long-term memory)
Long-term strengthening of synaptic connections involves
the induction of new genes in the neuron
an increase in the number of functional synapses
Genes know when to strengthen a synapse. Genes manufacture synapse-strengthening proteins. The cell’s nucleus “listens” to the cell’s action potential to determine when to strengthen a synapse and make a memory last.
CREB is turned on by genes and vice versa
CREB= a molecular switch for the formation of LTM.
CREB is required for the stability of initial and reactivated memories.
Gene zif268 is associated with learning and memory.
It is turned on by hippocampal neuron firing.
When the membrane depolarizes the machinery in the nucleus listens to the output of the neuron to decide whether to synthesize memory-fixing proteins.
Turn on active Genes genes
knockout-mouse or fly (Drosphilia)
tells us what genes are necessary to develop a normal learning and memory phenotype in the adult.
These knockout lines do not give us access to all the molecules in the adult brain that participate in memory encoding.
Knockout fly used in experiment in next movie clip.
Master genes rule cascade of genes genes1
Learning genes in Drosphilia
4 mutants obtained from behavioral screens: dunce , rutabaga , amnesiac and linotte .
(3 of the 4 mutants affect molecules that are involved in learning).
the mutant dunce seemed to affect learning the most
Environmental modification of heritable behaviors (nature + nurture)