Handwrite the basic steps & function of DNA Replication – submit. 1-2 pages
Chapter 12 Biology Sylvia S. Mader Michael Windelspecht Chapter 12 Molecular Biology of the Gene Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› 1 Slide 1 Outline 12.1 The Genetic Material 12.2 Replication of DNA 12.3 Gene Expression: RNA and the Genetic Code 12.4 Gene Expression: Transcription 12.5 Gene Expression: Translation Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 2 The Genetic Basis of Eye, Hair, and Skin Coloration All life on Earth contains the four bases of DNA: A, G, C, and T. These bases are molecules and code for biological parts such as the proteins that make skin, bones, and eyes. Different combinations of these bases make up genes. MC1R is a gene that contributes to skin, hair, and eye color in humans and is found in the nucleus of every cell. Some of the cells in skin become specialized pigment-making cells called melanocytes. Humans have variations in their MC1R that come from their ancestry. Differences in the DNA base sequence can alter gene expression, which affects how much melanin is produced. Everyone has melanin genes, but each individual’s gene expression is determined from information in their DNA. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 3 12.1 The Genetic Material Frederick Griffith investigated virulence of Streptococcus pneumoniae. He concluded that virulence could be passed from a dead strain to a nonvirulent living strain. Transformation Further research by Avery et al. Discovered that DNA is the transforming substance DNA from dead cells is incorporated into the genome of living cells. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 4 The Genetic Material (1) DNA and proteins were the candidates for the hereditary material. Proteins contain 20 amino acids that can be sequenced in different ways. DNA and RNA each contain only four types of nucleotides. Requirements for the genetic material: Must be able to store genetic information Must be stable and able to be replicated accurately during cell division and transmitted from generation to generation Must be able to undergo mutations to provide genetic variability Researchers showed that DNA can fulfill all these functions. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 5 The Genetic Material (2) Griffith’s Transformation Experiment Mice were injected with two strains of pneumococcus, an encapsulated (S) strain and a non-encapsulated (R) strain. The S strain is virulent (the mice died); it has a mucous capsule and forms “shiny” colonies. The R strain is not virulent (the mice lived); it has no capsule and forms “dull” colonies. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 6 Griffith’s Transformation Experiment Injected live S strain has capsule and causes mice to die. Injected live R strain has no capsule and mice do not die. Injected heat-killed S strain does not cause mice to die. Injected heat-killed S strain plus live R strain causes mice to die. Live S strain is withdrawn from dead mice. 12-‹#› Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Slide 7 The Genetic Material (3) Avery, MacLeod, and McCarty’s Experiment Scientists argued that DNA lacked variability to be able to store genetic information. Avery and colleagues used enzymes that break down DNA (DNase), or RNA (RNase), or protein (protease) in separate experiments to digest the substance which allowed Streptococcus to produce a capsule and become virulent. The only enzyme that had an effect was the DNase, which prevented the “transformation” from occurring. These experiments show that DNA was the transforming substance. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 8 The Genetic Material (4) Hershey and Chase’s Experiment They used a virus called a T phage, composed of radioactively labeled DNA and coat proteins (in two separate experiments), to infect E. coli bacteria. They discovered that radioactively labeled DNA, but not protein, ended up inside the bacterial cells, causing them to become transformed. Only the genetic material could have caused this transformation. This experiment showed that only DNA, and not protein, was the genetic material. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 9 The Genetic Material (5) Transformation of organisms today: The result is the so-called genetically modified organisms (GMOs). Invaluable tool in modern biotechnology today Commercial products that are currently much used Green fluorescent protein (GFP) used as a marker A jellyfish gene codes for GFP. The jellyfish gene is isolated and then transferred to a bacterium, or the embryo of a plant, pig, or mouse. When this gene is transferred to another organism, the organism glows in the dark. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 10 The Genetic Material (6) Viral DNA is labeled (yellow). When bacteria and viruses are cultured together, radioactive viral DNA enters bacteria. Agitation in blender dislodges viruses. Radioactivity stays inside bacteria. Centrifugation separates viruses from bacteria and allows investigator to detect location of radioactivity. Viral capsid is labeled (yellow). When bacteria and viruses are cultured together, radioactive viral capsids stay outside bacteria. Agitation in blender dislodges viruses. Radioactivity stays outside bacteria. Centrifugation separates viruses from bacteria and allows investigator to detect location of radioactivity. 12-‹#› Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Slide 11 The Genetic Material (7) DNA contains: Two nucleotides with purine bases Adenine (A) Guanine (G) Two nucleotides with pyrimidine bases Thymine (T) Cytosine (C) Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 12 The Genetic Material (8) Chargaff’s Rules: The amounts of A, T, G, and C in DNA: Are constant among members of the same species Vary from species to species In each species, there are equal amounts of: A and T G and C All of this suggests that DNA uses complementary base pairing to store genetic information. Each human chromosome contains, on average, about 140 million base pairs. The number of possible nucleotide sequences is . Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 13 Nucleotide Composition of DNA Purine nucleotides Pyrimidine nucleotides c. Chargaff’s data Table 12.1 DNA Composition in Various Species (%) SpeciesATGC Homo sapiens (human)31.031.519.118.4 Drosophila melanogaster (fruit fly)27.327.622.522.5 Zea mays (corn)25.625.324.524.6 Neurospora crassa (fungus)23.023.327.126.6 Escherichia coli (bacterium)24.624.325.525.6 Bacillus subtilis (bacterium)28.429.021.021.6 12-‹#› Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Slide 14 The Genetic Material (9) X-Ray diffraction: Rosalind Franklin studied the structure of DNA using X-rays. She found that if a concentrated, viscous solution of DNA is made, it can be separated into fibers. Under the right conditions, the fibers can produce an X-ray diffraction pattern. She produced X-ray diffraction photographs. This provided evidence that DNA had the following features: DNA is a helix. Some portion of the helix is repeated. A colleague of Franklins, Wilkins, showed her photo to James Watson, who understood its significance about DNA’s structure. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 15 X-Ray Diffraction of DNA 12-‹#› Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Slide 16 The Genetic Material (10) The Watson and Crick Model (1953) Double helix model is similar to a twisted ladder. Sugar-phosphate backbones make up the sides. Hydrogen-bonded bases make up the rungs. The two DNA strands are antiparallel. Information stored in DNA must be read in the 5 prime to 3 prime direction so DNA is replicated in a 5 prime to 3 prime direction. Complementary base pairing ensures that a purine is always bonded to a pyrimidine (A with T, G with C). They received a Nobel Prize in 1962. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 17 Watson and Crick Model of DNA 12-‹#› Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Slide 18 12.2 Replication of DNA DNA replication is the process of copying a DNA molecule. Semiconservative replication: Each strand of the original double helix (parental molecule) serves as a template (mold or model) for a new strand in a daughter molecule. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 19 Semiconservative Replication The mechanism of DNA replication The products of replication Robert Brooker, et al, Biology, 2e. New York, NY: McGraw-Hill Education, Copyright © 2011 McGraw-Hill Education. All rights reserved. Used with permission 12-‹#› Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Slide 20 Replication of DNA (1) Replication requires the following steps: Unwinding, or separation, of the two strands of the parental DNA molecule by the DNA helicase enzyme Single-stranded binding proteins (SSB) attach to newly separated DNA and prevent helix from re-forming. Complementary base pairing between a new nucleotide and a nucleotide on the template strand DNA primase places short primers on the strands to be replicated. Polymerase recognizes RNA and begins DNA synthesis. The two strands are replicated differently: leading and lagging strands. Joining of nucleotides in the lagging strand by DNA ligase form the new strand. Each daughter DNA molecule contains one old and one new strand. Copyright ©2019 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12-‹#› Slide 21 Replication of DNA (2) Prokaryotic Replication Bacteria have a single circular loop of DNA. Replication moves around the circular DNA molecule in both directions. It produces two identical circles. The process begins at the origin of replication.