北京大学：《微生物学》课程PPT教学课件（英文版）Chapter 5 Macromolecules and Molecular Genetics

Chapter 5 Macromolecules and molecular genetics The key informational macromolecules in prokaryotic and eukaryotic cells are DNA RNA, and protein Molecular genetics deals with the mechanisms by which the information in DNA is replicated and by which it can be transcribed into rna and translated into specific proteins

Chapter 5 Macromolecules and Molecular Genetics The key informational macromolecules in prokaryotic and eukaryotic cells are DNA, RNA, and protein. Molecular Genetics deals with the mechanisms by which the information in DNA is replicated, and by which it can be transcribed into RNA and translated into specific proteins

Central Dogma of Molecular Biology 中心法则 One-way transfer of genetic information from nucleic acid Replication to protein is call Central Dogma of DNA Molecular Biology Transcription RNA Translation Protein

Central Dogma of Molecular Biology 中心法则 One-way transfer of genetic information from nucleic acid to protein is call Central Dogma of Molecular Biology

Information ransfer in Prokaryotes and Eukaryotes Prokaryotes Gene A Gene B DNA Transcription mRNA Coding region A Coding region B Translation Prot A B

Information Transfer in Prokaryotes and Eukaryotes Prokaryotes

NUCLEUS DNA Exon 1 Intron 1 Exon 2 I Intron 2 3 ↓ Transcription Primary RNA [Exon 1I Intron 1T Exon 2 intron 2 Exon 3 transcript RNA processing Introns excised during processing Mature mRNA Transport to the cytoplasm mRNA Eukaryotes CYTOPLASM

Eukaryotes

DNA SYnthesis proceeds 523 5- Groving strand 3 A: Adenine 2 G: Guanine OH 2 T: Thymine 3 OH C: Cytosine 2 2 CH? CH2 P 2 3+ Parental strand -5

DNA Synthesis proceeds 5’ 3’ A: Adenine G: Guanine T: Thymine C: Cytosine

Replication of dna proceeds by insertion of a new nucleoside triphosphate at the free 3-hydroxyl end, with loss of two phosphate Chain Elongation p P 5- Growing strand 3 OH 尺 人 CH 2 OH 2 CH2 P 2 CH2 Parental strand 5

Replication of DNA proceeds by insertion of a new nucleoside triphosphate at the free 3’-hydroxyl end, with loss of two phosphate

helical DnA double tum helix groove any important proteins interact backbone with the mayor groove o DNA double hel

DNA double helix Many important proteins interact with the major groove of DNA double helix

How DNA is supercoilded and relaxed Enzyme involved in supercoiling (in bacteria) DNA gyrase(旋转酶): DNA Topoisomerase I(DNA拓朴异构酶I) Enzyme involved in removing supercoiling DNA gyrase DNA TopOISOmerase I Two antibiotics(Nalidixic acid and Novobiocin) inhibit the action of DNA

How DNA is supercoilded and relaxed Enzyme involved in supercoiling (in bacteria): – DNA gyrase (旋转酶）： • DNA Topoisomerase II (DNA拓朴异构酶II) Enzyme involved in removing supercoiling: – DNA gyrase: • DNA Topoisomerase I Two antibiotics (Nalidixic acid and Novobiocin) inhibit the action of DNA

Secondary Structure of DNA DNA bending: involving several runs of five to six adenines(in the same strand), each separated by four or five bases, Inverted repeat: regions of DNA containing repeated sequences in inverse orientation, leading to a stem-loop(茎—环); Sticky end: DNA with single-strand complementary sequences at the end, this can form a hairpin, linear DNA can form a cycle with their sticky end These structures influence dna interaction with proteins

Secondary Structure of DNA DNA bending: involving several runs of five to six adenines (in the same strand), each separated by four or five bases; Inverted repeat: regions of DNA containing repeated sequences in inverse orientation, leading to a stem-loop (茎—环）; Sticky end: DNA with single-strand complementary sequences at the end, this can form a hairpin, linear DNA can form a cycle with their sticky end. These structures influence DNA interaction with proteins

The effect of temperature on DNA Structure Two hydrogen bonds hold adenine-thymine(A-t) together Three hydrogen bonds hold guanine-cytosine(G C)together; Thus, G-C pairs are stronger than A-T pairs The separation of double stranded dna by heating is called melting DNA with higher GC content has higher melting temperature Organisms living at high T has higher GC content

The effect of temperature on DNA structure Two hydrogen bonds hold adenine-thymine (A-T) together; Three hydrogen bonds hold guanine-cytosine (G￾C) together; Thus, G-C pairs are stronger than A-T pairs; The separation of double stranded DNA by heating is called melting; DNA with higher GC content has higher melting temperature; Organisms living at high T has higher GC content