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Lecture 11

BIOL 3113 Lecture Notes - Lecture 11: Gene Duplication, Transfer Dna, Dna Replication

Course Code
BIOL 3113
Barbara S

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11 Genetic Variation
Although a stable genome is essential for the existence of both the individual and the
species, the origin of the differences between individuals and the origin of species
depends on the ability of the genome to undergo change
Conditions of change:
*must be heritable - affect germ line
*must not prevent the individual from reproducing
Genetic changes that offer an organism a selective advantage are the most likely to be
Main sources of genetic variation:
*mutation within a gene - point mutations
change a single nucleotide, duplicate or delete one or more nucleotides in gene DNA
usually a results of rare “mistakes” made during DNA replication or failures in DNA
repair after DNA damage
*gene duplication
existing gene, its part or large segment of DNA can be duplicated
It creates a set of closely related genes in a single cell. After additional mutations in cell
progeny, duplicated genes can assume functions distinct from those of the original gene
source of genetic novelty for evolving organisms
Duplications of oncogenes- common cause of many cancers
*gene deletion
Individual genes or blocks of genes can be lost through chromosome breakage and
failures to repair
*exon shuffling
two or more existing genes can be broken and rejoined to make a hybrid gene
containing DNA segments from different genes
can generate proteins with new combinations of protein domains
*horizontal (intercellular) gene transfer
piece of DNA can be transferred from the genome of one cell to the genome of another
cell or to the genome of another species
common in procaryotes, rare in eukaryotes
Conjugation - process by which bacterial cells can horizontally transfer DNA
Plasmids often carry genes for antibiotic resistance and can be transferred from
species to species
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