清华大学：《分子生物学》课程PPT教学课件（基因ene）第二章 从基因到基因组（From Genes to Genomes）

Chapter 2 From Genes to Genomes 清革大当

Chapter 2 From Genes to Genomes

2.1 Introduction We can think about mapping genes and genomes at several levels of resolution: A genetic (or linkage)map identifies the distance between mutations in terms of recombination frequencies A linkage map can also be constructed by measuring recombination between sites in genomic DNA A restriction map is constructed by cleaving DNA into fragments with restriction enzymes and measuring the distances between the sites of cleavage. The ultimate map is to determine the sequence of the DNA From the sequence.we can identify genes and the distances between them 清菜大当

2.1 Introduction We can think about mapping genes and genomes at several levels of resolution: A genetic (or linkage) map identifies the distance between mutations in terms of recombination frequencies. A linkage map can also be constructed by measuring recombination between sites in genomic DNA. A restriction map is constructed by cleaving DNA into fragments with restriction enzymes and measuring the distances between the sites of cleavage. The ultimate map is to determine the sequence of the DNA. From the sequence, we can identify genes and the distances between them

2.1 Introduction 2.2 The nature of interrupted genes 2.3 Organization of interrupted genes may be conserved 2.4 Exon sequences are conserved but introns vary 2.5 Genes can be isolated by the conservation of exons 2.6 Genes show a wide distribution of sizes 2.7 Some DNA sequences code for more than one protein 2.8 How did interrupted genes evolve? 2.9 The scope of the paradigm 清苇大当

2.1 Introduction 2.2 The nature of interrupted genes 2.3 Organization of interrupted genes may be conserved 2.4 Exon sequences are conserved but introns vary 2.5 Genes can be isolated by the conservation of exons 2.6 Genes show a wide distribution of sizes 2.7 Some DNA sequences code for more than one protein 2.8 How did interrupted genes evolve? 2.9 The scope of the paradigm

2.2 Genes can be mapped by restriction cleavage bp is an abbreviation for base pairs; distance along DNA is measured in bp Restriction enzymes recognize specific short sequences of DNA and cleave the duplex (sometimes at target site,sometimes elsewhere. depending on type) Restriction map is a inear array of sites c DNA cleaved 情菜大当

bp is an abbreviation for base pairs; distance along DNA is measured in bp. Restriction enzymes recognize specific short sequences of DNA and cleave the duplex (sometimes at target site, sometimes elsewhere, depending on type). Restriction map is a linear array of sites on DNA cleaved by various restriction enzymes. 2.2 Genes can be mapped by restriction cleavage

NA八入NN 2.2 Genes can be Cleave with Cleave with enzyme A enzyme B mapped by restriction cleavage Electrophorese Electrophorese Electrophorese A-fragments control DNA B-fragments ↓ Figure 2.1 DNA can be 2600.mm 2500 2100 2000 cleaved by restriction 1400 1500 1000 1000 18 enzymes into fragments 500 500 that can be separated by ge electrophoresis. Fragment sizes Control consists Fragment sizes compared 清菜大当 of fragments compared with control of known size with control

Figure 2.1 DNA can be cleaved by restriction enzymes into fragments that can be separated by gel electrophoresis. 2.2 Genes can be mapped by restriction cleavage

2.2 Genes Individual Individual Total DNA A-fragments B-fragments digested can be are digested are digested with both with enzyme B with enzyme A enzymes mapped by 101ch 导 110mh 205 品 restriction 山 cleavage ↓↓↓↓ Figure 2.2 Double digests define the 90中 90中 90中 cleavage positions 000 0时 000 0g0 of one enzyme with 80 600 regard to the other 2op 500 清菜大当

Figure 2.2 Double digests define the cleavage positions of one enzyme with regard to the other. 2.2 Genes can be mapped by restriction cleavage

2100 A The A-2100 2.2 Genes can 2ene发 1 B-cutting site be mapped by 1900 restriction "2i00 A-digest fragm ents cleavage m mmmmmmmmmmmm mmm Double digest Overlap with the B-2500 traqment Figure 2.3 1900 extendsthe map -"2500 digest fragm ents to the right A restriction map can be "2U而 .→月 constructed by Overlap with B- T亚.中亚.，d 1200 extends m ap relating the A- to lef ovenap wth ←"i00≥ 1900 A-1400 extends ←一1200 map to right fragments and B- "250" fragments through the overlaps seen A Left end of map is with double digest dentified by A- 1000&B-1200 fragm ents,right fragments. 1900 end is identifed by 2500 .B73→ A-500andB-1300 清菜大当

Figure 2.3 A restriction map can be constructed by relating the A￾fragments and B￾fragments through the overlaps seen with double digest fragments. 2.2 Genes can be mapped by restriction cleavage

2.2 Genes can be mapped by restriction cleavage Figure 2.4 When Restriction map restriction fragments are identified by Fragments identified on gel their possession of a A-G (unbroken) labeled end,each A-B-C-D-E-F fragment directly shows the distance BE-B-E of a cutting site A-B-C from the end B Successive A 1re9ien8中crease in length by the distance between adjacent restriction Labeled end sites 情菜大当

Figure 2.4 When restriction fragments are identified by their possession of a labeled end, each fragment directly shows the distance of a cutting site from the end. Successive fragments increase in length by the distance between adjacent restriction sites. 2.2 Genes can be mapped by restriction cleavage

2.2 Genes can be mapped by restriction cleavage AB A B A 1000200 1900 60800500 Figure 2.5 A restriction map is a linear sequence of sites separated by defined distances on DNA.The map identifies the sites cleaved by enzymes A and B.as defined by the individual fragments produced by the single and double digests 清菜大当

Figure 2.5 A restriction map is a linear sequence of sites separated by defined distances on DNA. The map identifies the sites cleaved by enzymes A and B, as defined by the individual fragments produced by the single and double digests. 2.2 Genes can be mapped by restriction cleavage

2.3 How variable are individual genomes? Haplotype is the particular combination of alleles in a defined region of some chromosome.in effect the genotype in miniature.Originally used to described combinations of MHC alleles.it now may be used to describe particular combinations of RFLPs SNP(single nucleotide polymorphism)is any site at which a single nucleotide has changed when two (haploid)genomes are compared 清菜大当

Haplotype is the particular combination of alleles in a defined region of some chromosome, in effect the genotype in miniature. Originally used to described combinations of MHC alleles, it now may be used to describe particular combinations of RFLPs. SNP (single nucleotide polymorphism) is any site at which a single nucleotide has changed when two (haploid) genomes are compared. 2.3 How variable are individual genomes?