Transcript Recombination, Mutation, Genetic Drift, Gene Flow

Recombination,
Mutation, Genetic Drift,
Gene Flow
Also evolution 
Recombination
 Remember



This is when recombination occurs
Shuffling of chromosomes/genes/alleles
Also crossing over
 Remember

Meiosis?
fertilization?
Coming together of shuffled genes
 New
alleles not created, just
rearranged for more genetic variability
Mutations
 Creates
new alleles
 Beneficial, neutral, or lethal
 Passed on to new generations if they arise
in gametes
 Can reduce chances of survival and
reproduction
 If
it causes severe reductions, usually ends with
death
 Neutral
mutation changes base sequence but
has no effect on survival or reproduction
mutation ex. – corn plant has a
mutation that makes it grow faster or larger
giving it best access to sunlight and nutrients
 Beneficial
 Neutral
mutation might prove helpful if the
environment changes
Genetic Drift
 Random
changes in allele frequencies over
time
is greatest in small populations –
leads to loss of genetic diversity
 Effect

Allele will become more or less prevalent in
small pops
 Bottleneck
 and
Founder Effect
Bottleneck
 Drastic
reduction in population size
because of severe pressure
Founder Effect
 A few
individuals establish a new
population
 Unpredictable genetic shifts occur
Gene Flow

Physical movement of alleles into and out of a
population

Opposes the effects of mutation, natural
selection, and genetic drift

Keeps populations similar to one another

Increases genetic variability in that new
population
Cladograms
 Aka.
Phylogenetic tree, branching tree,
evolutionary tree
 Lines not still apparent at present are
extinct
 Do not have to all face the same way
Hardy-Weinberg Principle
1.
2.
3.
4.
5.

Random mating
Large population
No movement
No mutations
No natural selection
Allele frequency in a population will remain
constant
H-W Principle
 p2
+ 2pq + q2 = 1
p + q = 1
p2 = frequency of homozygous dominant
2pq = frequency of heterozygous
q2 = frequency of homozygous recessive
p = dominant allele
q = recessive allele
H-W Principle
1 in 1700 US Caucasian newborns have cystic
fibrosis. C for normal is dominant over c for
cystic fibrosis.
 What percent of the above population have
cystic fibrosis (cc or q2)?
 What percent of the population do not have
cystic fibrosis and are homozygous dominant
(CC or p2)?
 What percent of the population is
heterozygous?