genome maps - linkage maps showing relative location of genes
- 1st map made in 1911 when 5 genes of Drosophila mapped
- distances measured in centimorgans (cM)
- genetic maps - distances between genes found by recombination frequencies
- physical maps - diagrams showing relative landmarks within sequences
- landmark - specific DNA sequences, where restriction enzymes cut DNA
- contig - contiguous segment of genome made from pieces cut by restriction enzymes
- sequenced-tagged sites (STS) - 100-500 base-pair sequence of a clone
- physical map can be made by overlapping STSs
- useful when 2 different groups working on certain nonsequenced DNA
sequencing - automated sequencing required for the very large genomes
- automated sequencers - provides accurate sequences for up to 500 base-pairs
- errors still possible, 5-10 copies used
- DNA prepared w/ fluorescent nucleotides, unlabeled nucleotides
- fluorescent nucleotides lack hydroxyl groups, halt replication
- DNA separated by size (1st base in sequence found in shortest band, last base in sequence found in longest band)
- artificial chromosome - used to clone larger DNA pieces
- contained replication origin (to replicate independently of genome) and centromere sequences (for stability)
- bacterial artificial chromosomes (BAC) - used for large-scale sequencing, accepts DNA inserts 100-200kb long
- clone-by-clone sequencing - physical mapping followed by sequencing
- cuts DNA fragments which are each cloned into smaller fragments
- shotgun sequencing - sequencing all the clone fragments all at once, uses computer to put together overlaps
- assembles consensus sequence from multiple copies of sequenced regions
- doesn’t use extra info about genome
human genome project - 3.2 gigabase nucleotide sequence in humans
- number of genes doesn’t indicate complexity of organism (rice has more genes than humans)
- physical map finished on June 26, 2000
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