Download Principles of Genetics, A BRIEF INTRODUCTION

CEng 713 Evolutionary Computation, Lecture Notes
Principles of
Genetics, A BRIEF
INTRODUCTION
Darwin's Theory of Evolution
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The common descent of all organisms from a
single ancestor.
The manifestation of novel traits in a lineage.
The mechanisms that cause some traits to
persist while others perish.
Forces of evolution:
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Survival of the fittest
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Recombination,mutation
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Gene flow
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Genetic drift
Population Genetics
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Investigates genetic variation among
individuals withing groups (populations, gene
pools)
Investigates the genetic basis for
evoluitionary change and seeks to
understand how patterns vary geographically
and through time.
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How genetic diversity affected by evolution?
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Mutation
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Selection
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Genetic drift
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Migration
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Non-random mating -
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Hardy-Weinberg assumptions:
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population is infinetely large
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mating is random
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no natural selection
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no mutation
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no migration
Hardy-Weinberg law:
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If assumptions are met, population will be in
genetic equililibrium
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Genetic Drift
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Random increase or decrease in the trait
frequencies in the gene pool of a population.
Sampling affect. Each population is a sample
of its parent population.
For small populations, sampling errors will be
significant.
An allele can be fixed (p=1) or go extinct
(p=0)
Gene Flow
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Gene flow/migration:
movements of genes from one population to
the other
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Introduce and spreads unique allelles to new
population
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Allele frequencies of populations change
Natural Selection and Adaptation
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Natural selection and adaptation
Ecological selection:
organisms which survive and reproduce increase
the frequency of their genes in the gene pool
wrt. organisms who cannot survive
Sexual selection:
organisms which are more attractive to the
opposite sex because of their features reproduce
more and thus increase the frequency of those
features in the gene pool
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Purifying selection: eliminates the deterious mutations
Positive selection: increase frequency of beneficial
mutations
Balancing selection: maintain the variance of population
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heterozygous forms are more fit than the homozygous
forms
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frequency dependent selection: rare variants have high
fitnes or sexual attractivity.
Baldwinian evolution: culturial species that are able the
learn can change the environment to introduce new
selection forces.
Speciation
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Creation of two or more species from one.
Allopatric speciation: geographical isolation.
Habitat fragmentation, migration.
Sympatric speciation: same habitat.
Adaptive Landscape
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genetic compositions with mean fitness is
high gets a higher position in the landscape.
Selection move population to high fitness
(probably a local maxima)
Drift may move the population to lower
position in the landscape.
Interaction of species, parasites, symbiotic
life, migration, climate conditions,... Fitness
definition is complicated.
Chromosome
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DNA: nucleic acid that contains the genetic
instructions specifying the biological development of
all cellular forms of life
Chromosome: macromolecule package of DNA.
A sequence of nucleotide
bases in double helix
structure.
Human genetic information:
~3,000,000,000 bases,
32,000 genes in
46 chromosomes.
Structure of the DNA
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Double helix model
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Nucleotides, 4 bases:
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Adenine
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Thymin (only in DNA)
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Cytosine
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Guanine
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Uracil (only in RNA)
Purpose:
Protein synthesis
Gene Structure
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Sequence of 3 nucleotide bases form a codon. Each
codon defines an amino acid.
Each gene defines the information for synthesis of a
protein.
Introns: non-coding segments. they are not realized
in the phenotype.
Exons: coding segments
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enhancer and promoter codons facilate RNA
alignment with the gene.
genes may overlap. Introns in one gene can be exon
in the other.
Several genes can affect a phenotypical
characteristic.
existence of a gene can affect the activityof the
other (ephistasis)
A more complicated picture.
Transcription and Translation
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Transcription of data in a gene
into mRNA, messenger RNA.
tRNA, transfer RNA, transports the
RNA sequence to ribosome
rRNA, ribosomal RNA, forms
complexes called ribosomes with
protein
Reproduction
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During the Meiosis, two chromosomes are
crossovered.
Crossover
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During crossover, offspring gets half of its
genome from either parents.
Mutation
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Error during the crossover of two DNA sequences.
Some portion of DNA can be deleted, inserted,
inverted during the copying.
There is a repair mechanism however not all of the
sequences can be repaired.
So genes can have:
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point mutation
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frameshift
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transposition
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inversion
Glossary
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Allele: An alternative form of a gene that occurs at a specified
chromosomal position (locus)
Codon: A group of thre nucleotide bases within the DNA that
encodes a single amino acid or start and stop information for
the transcription process.
Crossover: A process of information exchange of genetic
material that occurs between adjacent chromatids during
meiosis.
Deme: An independent subpopulation.
Diploid: In diploid organisms, each body cell carries two sets of
chromosomes; each chromosome exists in two homolohous
forms, one of which is phenotypically realized.
DNA: Deoxyribonucleic acid, a double-stranded macromolecule
of hlical structure determining building plan of an organism.
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Exon: A region of codons within a gene that is expressed for
the phenotype of an organism.
Intron: A region of codons within a gene that do not bear
genetic information that is expressed for the phenotype of an
organism.
Gamete: A haploid germ cell that fuses with another in
fertilization to form a zygote.
Gene: A unit of codons on the DNA that encodes the synthesis
for a protein.
Genome: The total genetic information of an organism.
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Genotype: The sum of inherited characters maintained within
the entire reproducing population.
Phenotype: The behavioiral expression of the genotype in a
specific environment.
Locus:A particular location on a chromosome.
Meiosis: The process of cell division in diploid organisms
through which germ cells (gametes) are created.
Mitosis: The process by which a cell separates its duplicated
genome into two identical halves.
Niche: Adapatatoin of species occurs with respect to any major
kind of environment, the adaptive zone of this species.
Polygeny: The combined influence of several genes on a single
phenotypical characteristics.
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RNA: Ribonucleic acid. The transcription process in the cell
nbucleus generates a copy of the nucleitode sequence on the
coding strand of the DNA.