Chapter 24 Flashcards
Genomics
Comparing genomes (entire D N A sequences) of different species provides a powerful new tool for exploring the evolutionary divergence among organisms
Comparative Genomics
Genomes of viruses and bacteria evolve in a matter of days
Complex eukaryotic species evolve over millions of years
Plant, fungal, and animal genomes have unique and shared genes
3814 gene families are shared by every plant.
Move onto land arose in 3006 new gene families.
Moss and flowering plants very different but share 80% of developmental genes.
Mosses to plants with internal transport required 516 more gene families.
Transition to flowering plants required 1350 more gene families.
Compare plants with animals and fungi
Of remaining genes, many are similar to those found in animal and fungal genomes
Genome Size
Genome size and gene number vary greatly among eukaryote species
Polyploidy
Three or more chromosome sets
Autopolyploids
genome duplication within a single lineage.
Allopolyploids
hybridization of two lineages followed by genome duplication
Paleopolyploids
ancient polyploids
Synthetic polyploids
Crossing plants most closely related to ancestral species and chemically inducing chromosome doubling.
Polyploidy can alter gene expression
During early generations after polyploidization, changes in gene expression are observed
Barbara McClintock
Hypothesized that transposons could be mobilized by genome shock.
Transposable
(mobile) genetic elements
Aneuploidy
Gain or loss of an individual chromosome
Gene duplication
One of the greatest sources of novel traits
Paralogues
two genes within an organism that have arisen from the duplication of a single gene in an ancestor
Orthologues
reflects conservation of a single gene from a common ancestor
Conservation of synteny
when the common ancestral sequence has been preserved in both species
Gene inactivation
Loss of gene function
Olfactory receptor (OR) genes
Inactivation best explanation for our reduced sense of smell relative to other mammals
Noncoding D N A
Much of the genome is noncoding-D N A (ncD N A)
Repetitive D N A is often retrotransposon D N A
30% of animal and 40–80% of plant genomes
Conserved noncoding regions (C N Cs)
evolve more slowly than expected assuming no function
Horizontal gene transfer (H G T)
Genes hitchhike from other species
Also called lateral gene transfer.
Can lead to phylogenetic complexity.
Likely most prevalent very early in the history of life.
vertical gene transfer (V G T)
genes passed generation to generation
