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Blueprint of Life Topic 17: DNA Functioning

Blueprint of Life Topic 17: DNA Functioning . Biology in Focus, HSC Course Glenda Childrawi , Margaret Robson and Stephanie Hollis. DOT POINT(s). describe the process of DNA replication and explain its significance. Introduction .

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Blueprint of Life Topic 17: DNA Functioning

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  1. Blueprint of LifeTopic 17: DNA Functioning Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis

  2. DOT POINT(s) • describe the process of DNA replication and explain its significance

  3. Introduction The discovery of the biochemical detail of the structure of DNA by Watson and Crick in 1953 (12 years after Beadle and Tatum’s work) brought about a better understanding of the biochemical functioning of DNA. www.nobelweekdialogue.org

  4. Introduction Besides storing and transmitting all the heredity information in every cell of an individual, DNA plays an active role in gene expression, central to cell functioning and determining the phenotype of living organisms. five30liveservice.wordpress.com

  5. Introduction The active functioning of DNA in the everyday activities of cells takes two forms: 1. DNA replication: in its hereditary role, DNA must be able to make an exact copy of itself so that when a cell divides, the resulting daughter cells each have a full complement of DNA. www.sciencesuperschool.com

  6. Introduction 2. protein synthesis: genes are expressed in terms of the protein products that they produce. Many of these proteins are enzymes, which control chemical functioning of cells. DNA directs the production of these proteins. culturingscience.wordpress.com

  7. Introduction Other proteins produced may form a structural part of the cell (e.g. the protein in cell membranes, pigment in skin and eyes, and silk in insect cocoons) and some proteins form essential chemicals such as hormones (e.g. insulin), defence proteins (e.g. antibodies) and transport proteins (e.g. haemoglobin). theelephantman.deviantart.com

  8. DNA Replication DNA replication is the production of two identical double stranded molecules of DNA from one original double helix molecule. The process of DNA replication in cells is termed semiconservative, as the two strands of the original DNA molecule separate and each gives rise to a new complementary strand. sharonchoi-sbi4u.blogspot.com

  9. DNA Replication This mechanism ensures that the genetic material is copied exactly. DNA replicates before cell division so that each cell can receive one full and exact copy of the coded instructions that control the basic life functions of the cell. bio4esobil2010.wordpress.com

  10. DNA Replication When Watson and Crick discovered the structure of DNA, they noted immediately that their model suggested a possible copying mechanism for the genetic material—if the strands separated, each could act as a template for the synthesis of a new, complementary strand and this is indeed what happens. alevelnotes.com

  11. The Process The process of DNA replication occurs in three steps: 1. The DNA double helix unwinds. Each DNA molecule is a double stranded helix. An enzyme called helicase causes the DNA helix to progressively unwind. www.nist.gov

  12. The Process 2. DNA unzips —that is, the two strands separate. The weak hydrogen bonds break between the complementary bases of the nucleotides on opposite strands and the two DNA strands separate, exposing the nucleotide bases. pinterest.com

  13. The Process If you think of DNA as a ‘ladder’, each ‘rung’ splits down the middle, creating a replication fork—beyond this point, the DNA resembles a flat ‘ladder’ where the sides are made up of a sugar–phosphate backbone and the ‘rungs’ are formed by complementary base pairs. truthfall.com

  14. The Process 3. Nucleotides are added to each single strand: Each separate strand of the existing DNA molecule acts as a template for the production of a new strand of DNA. Nucleotides (units made of sugar— phosphate—base) are picked up by the enzyme DNA polymerase and slotted in opposite their complementary base partner on each of the existing strands. www.personal.psu.edu

  15. The Process These nucleotides are picked up from a pool of nucleotides in the nuclear sap. Nucleotide pairing is specific. Adenine (A) always pairs with thymine (T) nucleotides. Guanine (G) always pairs with cytosine (C) nucleotides. www.bcscience.com

  16. The Process The direction in which nucleotide insertion occurs is antiparallel on the two opposite strands—on one strand it begins at the replication fork and goes towards the end of the strand, whereas on the other strand it begins at the end of the single strand and goes towards the replication fork. www.scienceprofonline.com

  17. The Process The base pairing is checked by another DNA polymerase enzyme which ‘edits’ any incorrect additions, to ensure accuracy. Incorrect base pairing will result in a change in the DNA base sequence, known as a mutation. www.rationalresponders.com

  18. Result of DNA Replication Each resulting DNA molecule contains one strand of the existing DNA molecule and a newly-synthesised strand. The replicated DNA molecules rewind into the double helix conformation, like the original molecule. vinodwadhawan.blogspot.com

  19. Result of DNA Replication The end result is that there are two molecules of DNA, each a double-stranded helix, and they are identical to each other and to the original molecule from which they formed. library.thinkquest.org

  20. The Significance of DNA Replication The genetic material of a cell must be transmitted from: ■ one cell to another during mitosis, allowing for growth and repair and maintenance of an organism ■ one generation to another during meiosis (e.g. when gametes are formed for sexual reproduction). www.biologyjunction.com

  21. The Significance of DNA Replication In each of these situations, it is necessary for the DNA to make an exact copy of itself—that is, DNA replication occurs. Replication of DNA ensures that the genetic code of a cell is passed on to each new daughter cell that arises from it. An exact replica or copy of the DNA must be produced so that the new cells have the same, distinctive message that the original cell had. If DNA replication goes wrong, this has a direct effect on the phenotype of the individual. www.biomedcentral.com

  22. Activity/Homework -Students to watch DNA Replication Video: http://youtu.be/FBmO_rmXxIw If time watch: http://youtu.be/zFVH9SqtJCM a

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