copyright cmassengale DNA and Replication Essential Question: How does the process of DNA replication allow for information to be retained and transferred? copyright cmassengale
copyright cmassengale Objectives Describe the process of DNA replication and its role in transmitting and conserving genetic information. copyright cmassengale
copyright cmassengale History of DNA Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins were composed of 20 different amino acids in long polypeptide chains copyright cmassengale
copyright cmassengale Transformation Fred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria He found that R strain could become virulent when it took in DNA from heat-killed S strain Study suggested that DNA was probably the genetic material copyright cmassengale
copyright cmassengale Griffith Experiment copyright cmassengale
copyright cmassengale History of DNA Chromosomes are made of both DNA and protein Experiments on bacteriophage viruses by Hershey & Chase proved that DNA was the cell’s genetic material Radioactive 32P was injected into bacteria! copyright cmassengale
copyright cmassengale Chargaff’s Rule Adenine must pair with Thymine Guanine must pair with Cytosine The bases form weak hydrogen bonds T A G C copyright cmassengale
copyright cmassengale DNA Structure copyright cmassengale
DNA Traits are passed from parent to offspring through DNA. DNA is genetic material found in the cell’s nucleus. DNA acts like a blueprint for the cells of an organism, instructing them how to put together materials to produce certain traits.
DNA Genes are segments of DNA that carry instructions for the traits of an organism from parent to offspring. Genes are located on chromosomes in the nuclei, or center of cells. Genes make protein which carries out a lot of the cells functions. {Ask students where the chromosomes are in this picture. Or ask them where the DNA is. Remind them that the mitochondria also have DNA.}
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copyright cmassengale DNA Stands for Deoxyribonucleic acid Made up of subunits called nucleotides Nucleotide made of: 1. Phosphate group 2. 5-carbon sugar (deoxyribose) 3. Nitrogenous base copyright cmassengale
copyright cmassengale DNA Nucleotide O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose) O copyright cmassengale
copyright cmassengale DNA P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A copyright cmassengale
copyright cmassengale DNA Two strands coiled around each other called a double helix. The strands are complementary (fit together and are opposite of each other. copyright cmassengale
copyright cmassengale Antiparallel Strands One strand of DNA goes from 5’ to 3’ (sugars) The other strand is opposite in direction going 3’ to 5’ (sugars) copyright cmassengale
copyright cmassengale Nitrogenous Bases Double ring PURINES Adenine (A) Guanine (G) Single ring PYRIMIDINES Thymine (T) Cytosine (C) A or G T or C copyright cmassengale
copyright cmassengale Base-Pairings Purines only pair with Pyrimidines Three hydrogen bonds required to bond Guanine & Cytosine C G 3 H-bonds copyright cmassengale
copyright cmassengale DNA Replication copyright cmassengale
copyright cmassengale Replication Facts DNA must be copied before a cell divides DNA is copied during the S or synthesis phase of interphase New cells will need identical DNA strands The process by which DNA is copied during the cell cycle is called replication. copyright cmassengale
copyright cmassengale DNA Replication Begins at Origins of Replication Two strands open forming Replication Forks (Y-shaped region) New strands grow at the forks Replication Fork Parental DNA Molecule 3’ 5’ copyright cmassengale
DNA Replication 1. Some enzymes start unzipping the double helix to separate the strands of DNA. The hydrogen bonds connecting the base pairs are broken.
DNA Replication 2. Other proteins hold the strands apart so that nucleotides can pair up with the DNA strands.
DNA Replication 3. When done, 2 complete DNA molecules will be left, each similar to the original helix.
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