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Unit 4A DNA Structure and replication

Unit 4A DNA Structure and replication. DNA (Deoxyribonucleic Acid). A nucleic acid Made up of nucleotides. Phosphate Group. O O=P-O O. 5. CH2. O. N. Nitrogenous base (A, T, C, or G). C 1. C 4. Sugar ( deoxyribose ). C 3. C 2. DNA Nucleotide.

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Unit 4A DNA Structure and replication

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  1. Unit 4A DNA Structure and replication

  2. DNA(Deoxyribonucleic Acid) • A nucleic acid • Made up of nucleotides

  3. Phosphate Group O O=P-O O 5 CH2 O N Nitrogenous base (A, T, C, or G) C1 C4 Sugar (deoxyribose) C3 C2 DNA Nucleotide

  4. DNA is a molecule that must sometimes be copied. When/why does the DNA need to be copied?

  5. How many different types of nitrogenous bases are found in DNA? _________ • What do purines have in common? _____________________ • What do pyrimidineshave in common? __________________ • If each nucleotide contains 1 nitrogen base, how many different types of DNA nucleotides can be formed? ______ • NOTE: Another type of nucleotide, Uracil (U), will replace the Thymine nucleotide in RNA molecules.

  6. P A • Here is an example of a nucleotide: • We normally draw a nucleotide using symbols/letters to represent the parts. • What does the "A" stand for? • What other letters could be used in that position?___________ • What does the "S" stand for?___________________________ • What does the "P" stand for?___________________________ S

  7. Phosphate Group P Notice that each nucleotide bonds with a nucleotide above and below it. This forms a strand of DNA. The two strands run in opposite directions. This is called antiparallel. The two strands are then twisted into a spiral shaped, double stranded structure called a double helix.

  8. Phosphate Group P The bonds that hold the nucleotides in a strand of DNA together are covalent bonds (highlight) The bonds in between the nitrogenous bases that connect the two strand are hydrogen bonds (draw in color)

  9. Phosphate Group P Circle a nucleotide on the drawing to the left What does each nucleotide have in common? How do nucleotides differ from each other? How many strands make up a molecule of DNA? ____ Adenine (A) pairs with Cytosine (C) pairs with

  10. If the sequence of nucleotides in one strand of a DNA molecule is T-A-C-G-G-T-C-A-A, what would be the complementary base pairs on the other strand? ______________________________

  11. Summarize DNA structure at the bottom of pg. 3

  12. Amino Acid and Polypeptide Structure • How many different amino acids could be used to form a single protein or polypeptide?_____ • What must happen to the polypeptide before it is a fully functioning “protein”?

  13. Who discovered the structure of DNA? • Erwin Chargaff • Determined that the percent of A was about equal to the percent of T in any DNA molecule. • Likewise, the percent of C was about equal to the percent of G. • This is known as Chargaff’s Rule • Why did he see this consistency?

  14. Using Chargaff’s Rule Percentage of Bases in Human DNA

  15. Rosalind Franklin • Used X ray diffraction • Her image hinted that DNA was two stranded and in a helical shape

  16. James Watson and Frances Crick • Won the Nobel Prize for determining the structure of DNA • Used info from Chargaff and Franklin Francis Crick James Watson

  17. Human Genome Project • Genome: the entire set of genetic information that makes up the DNA of an organism • Completed in 2003, the Human Genome Project (HGP) was a 13-year project coordinated by the U.S. Department of Energy and the National Institutes of Health.

  18. Goals of the Human Genome Project • identify all of the approximately 20,000-25,000 genes in human DNA • determine the sequence of the 3 billion base pairs that make up human DNA • store this information in databases for use by scientists everywhere • address the ethical, legal, and social issues (ELSI) that may arise from the project.

  19. Human Genome Project • What were three surprises for scientists after they sequenced the human genome? • What were two good things that came from sequencing the human genome?

  20. DNA Sequencing • the laboratory technique used to determine the exact sequence of A’s, T’s, C’s, and G’s in an individuals entire genome.

  21. Forms of DNA and How it is Organized • Where is DNA located? • Prokaryotic cytoplasm • Eukaryotic nucleus • Every body cell has a complete copy of DNA

  22. Forms of DNA • Prokaryotic- 1 circular loop • Eukaryotic- multiple linear (straight) strands found in 2 forms depending on the situation. 1. Chromosomes 2. Chromatin

  23. Forms of DNA (cont.) 1. Chromosome:tightly packed, or “condensed” strands of DNA. DNA forms these structures when the cell is dividing. Usually shown as an X-shape or doubled chromosome. • Histones - Proteins which act like spools for thread. DNA is wound around the histones.

  24. What comes to mind when you hear the word chromosome? What does a chromosome look like?

  25. Karyotypes • A picture of all of the chromosomes from one cell of an organism. • How many total chromosomes are in the karyotype? • These chromosomes are from a _________________.

  26. Forms of DNA (cont.) 2. Chromatin- loosely packed, or “working” form of DNA. The strands are loose and exposed so that the code or protein “recipes” can be read and proteins can be synthesized.

  27. Every species of eukaryotic organisms have a specific number of chromosomes in each cell:

  28. How many chromosomes do humans have? _______ • How long is the DNA in one human cell?__________ • How does that much DNA fit into a cell?

  29. Why have 2 different forms of DNA in your cells? • Chromosomes are useful because . • Chromatin is useful because   Why is the number of chromosomes different for different organisms?

  30. DNA Replication • DNA must be copied before cell division so that any new cells will have an IDENTICAL copy of the DNA from the original cell.

  31. Steps in DNA replication: 1. The enzyme DNA helicase unwinds and unzips the double helix and the 2 DNA strands are separated between the complementary nitrogenous bases.

  32. 2. The enzyme DNA polymerase helps to link free floating DNA nucleotides with the complementary nitrogenous bases on each of the two strands

  33. 3.) Covalent bonds join the nucleotides above and below each other on the new strands. And, the hydrogen bondsare formed between the complementary nitrogenous bases (from one strand to another).

  34. 4.) Each new DNA strand formed contains ONE parent (original) strand and ONE new daughter strand.

  35. Summary of Replication • DNA double helix splits into two strands • Each strand becomes a template for new nucleotides to bind • Base pairing allows for the correct sequence to be created on the new “complementary” strand Replication

  36. If an error is made during replication it is called a mutation.

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