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Chromosome-level Mutation. A B C D E F. G H I J K L M. A B C D E F G. D E F G H I J K L M. I H G J K L M. A B C. inversion. translocation.
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Chromosome-level Mutation A B C D E F G H I J K L M A B C D E F G D E F G H I J K L M I H G J K L M A B C inversion translocation
Processes of Gene Rearrangement A B C D C D E duplication B A C D E A B C D terminal deletion pericentric inversion A B C D E Eliminate A D C B E paracentric inversion A B C E A B C D E interstitial deletion breakage
Exchange of Genetic Information A B C D E F W X Y Z Translocation Centric fusion Z Y X C D E F A B C X Y Z W D E F
Terms for Comparing Gene Order Synteny : Occurence of two or more genes on a chromosome. Conserved Synteny : Synteny of orthologous genes between species.
Ambystoma Linkage Map 5251 cM (~93%)
Salamander Genome….BIG! Human Salamander Reptile
Genome-wide recombination is not proportional to chromosome # in Ambystoma genome Chom. Chrom. obligatory proportion size (Gbp) # Arms Map (cM) cM / Mb(A# * 50cM) obligatory cM/arm Mouse 2.7 20 20 1361 0.5 1000 0.73 68.1 Rat 2.6 21 33 1749 0.7 1050 0.94 53.0 Human 3.0 23 46 3615 1.2 1150 0.64 78.6 Chicken 1.2 38 44 3800 3.2 1900 0.58 86.4 Ambystoma 30.0 14 28 5152 0.2 700 0.27 184.0
Chromosomal Distribution of Orthologous Genes Salamander Salamander MOUSE HUMAN N = 338 Refseq database size = 16,800 N = 402 Refseq database size = 21,098 CHICKEN RAT N = 338 Refseq database size = 11,348 N = 236 Refseq database size = 12,427
Number of Conserved Syntenies Comparison #a #b Human 69 28 Mouse 82 24 Chicken 52 17 Rat 58 14 #a based on 2 or more orthologues #b based on 4 or more orthologues
Spatial Distribution of Orthologous Loci : Segmental Homology H U M A N G E N O M E (1-23) Lg1 Lg2 Lg3 Lg14 white met melanoid Salamander Genome
Conserved Synteny based upon 3 or more genes C H I C K E N G E N O M E (1-23) Lg1 Lg2 Lg3 Lg14 white met melanoid Salamander Genome
Candidate Genes sex Cross-Referencing melanoid white met
Primary Mechanism of Duplication : Unequal Crossing Over Crossing over Between Daughter Strands Addition (duplication) Deletion (tandom duplications) Crossing over Between Daughter Strands Addition Deletion
Concerted Evolution • Members of a gene family evolve in concert. • Mutations are transferred among members of the family (homogenization) • Mutations are spread to all individuals in the population (fixation).
Fate of Duplicated Loci • Both copies retain original function e.g. rRNA genes (2) Gain new function through mutation and selection e.g. globin genes (3) Become functionless pseudogenes e.g globin genes
a Duplication TD a b Speciation TS a b a b Species 2 Species 1 aandbare said to be paralogous genes aspecies1andaspecies2are said to be orthologous genes
Time of duplication may be estimated by observing the phylogenetic distribution of genes All vertebrates but jawless fish have a and b H1: Two independent gene losses H2: Duplication
Processed Pseudogene Creation of a processed pseudogene.
Fate of a Processed Pseudogene • Functional Jingwei (see your book, p. 464) Human phosphoglycerate kinase (PGK) Preproinsulin in some mammals • Nonfunctional • Examples are known for all gene types