tailieunhanh - Lecture Biology - Chapter 18: Genomics

Learning objectives of this chapter include: Define genome; discuss the breath of genomics; distinguish between genetic maps and physical maps; describe the different techniques used for sequencing a genome; discuss the pros and cons of using clone-by-clone sequencing versus shotgun sequencing;. | Genomics Chapter 18 Mapping Genomes Maps of genomes can be divided into 2 types -Genetic maps -Abstract maps that place the relative location of genes on chromosomes based on recombination frequency -Physical maps -Use landmarks within DNA sequences, ranging from restriction sites to the actual DNA sequence Physical Maps Distances between “landmarks” are measured in base-pairs -1000 basepairs (bp) = 1 kilobase (kb) Knowledge of DNA sequence is not necessary There are three main types of physical maps -Restriction maps -Cytological maps -Radiation hybrid maps Physical Maps Restriction maps -The first physical maps -Based on distances between restriction sites -Overlap between smaller segments can be used to assemble them into a contig -Continuous segment of the genome Molecular weight marker A A A A B B B 14 kb 5 kb A A 8 kb 9 kb 2 kb 9 kb 5 kb 3 kb 2 kb 2 kb 2 kb 2 kb 2 kb 3 kb 6 kb 5 kb 5 kb 5 kb 10 kb 10 kb 19 kb 9 kb 9 kb 8 kb 14 kb 14 kb 1. Multiple copies of a segment of DNA are cut with restriction enzymes. 2. The fragments produced by enzyme A only, by enzyme B only, and by enzymes A and B together are run side-by-side on a gel, which separates them according to size. 3. The fragments are arranged so that the smaller ones produced by the simultaneous cut can be grouped to generate the larger ones produced by the individual enzymes. 4. A physical map is constructed. DNA 0 enzyme A enzyme A + B enzyme B Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Physical Maps Cytological maps -Employ stains that generate reproducible patterns of bands on the chromosomes -Divide chromosomes into subregions -Provide a map of the whole genome, but at low resolution -Cloned DNA is correlated with map using fluorescent in situ hybridization (FISH) Physical Maps Physical Maps Radiation hybrid maps -Use radiation to fragment chromosomes randomly -Fragments are then recovered by fusing irradiated cell to another | Genomics Chapter 18 Mapping Genomes Maps of genomes can be divided into 2 types -Genetic maps -Abstract maps that place the relative location of genes on chromosomes based on recombination frequency -Physical maps -Use landmarks within DNA sequences, ranging from restriction sites to the actual DNA sequence Physical Maps Distances between “landmarks” are measured in base-pairs -1000 basepairs (bp) = 1 kilobase (kb) Knowledge of DNA sequence is not necessary There are three main types of physical maps -Restriction maps -Cytological maps -Radiation hybrid maps Physical Maps Restriction maps -The first physical maps -Based on distances between restriction sites -Overlap between smaller segments can be used to assemble them into a contig -Continuous segment of the genome Molecular weight marker A A A A B B B 14 kb 5 kb A A 8 kb 9 kb 2 kb 9 kb 5 kb 3 kb 2 kb 2 kb 2 kb 2 kb 2 kb 3 kb 6 kb 5 kb 5 kb 5 kb 10 kb 10 kb 19 kb 9 kb 9 kb 8 kb 14 kb 14 kb 1. Multiple copies of a segment