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DNA Replication

DNA Replication. I. Terms:. A. Genes- the segments of DNA that are the units of inheritance. Found on chromosomes. They control the development of traits . (hair color, blood type. Etc.).

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DNA Replication

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  1. DNA Replication

  2. I. Terms: • A. Genes- the segments of DNA that are the units of inheritance.

  3. Found on chromosomes.

  4. They control the development of traits. (hair color, blood type. Etc.)

  5. B. DNA –(Deoxyribonucleic acid) chemical that codes for proteins and controls the development of traits and cellular activities.

  6. II. Watson and Crick proposed a model for the DNA structure.

  7. III. Structure of DNA: • A. very large molecule

  8. B. Made of nucleotides. Each nucleotides consists of: • A phosphate group • a five carbon sugar (deoxyribose) • a nitrogen base

  9. Nitrogen base Phosphate group 5 carbon sugar

  10. C. The nucleotides are joined together by bonds between the phosphate group of one nucleotide and the sugar of the next nucleotide. They form chains called phosphate sugar chains.

  11. D. The DNA molecule is composed of two chains of nucleotides joined by weak hydrogen bonds between the nitrogen bases.

  12. The chains of nucleotides spiral around a common center, the shape is called the double helix or a twisted ladder.

  13. E. DNA Code

  14. E. The DNA code---The chains of nucleotides in a DNA molecule connect together by bonds according to a code called the DNA code.

  15. The code is determined by the order of the nucleotides.

  16. The four bases are A=adenine, G=guanine, C=cytosine, T=thymine • A joins to thymine, G joins to cytosine • The order of the bases determine the genetic make up of the individual.

  17. F. DNA vs. RNA • DNA RNA • Double stranded Single Stranded • Contains deoxyribose Contains ribose sugar sugar • Has A, G, C, T Has A, G, C, U (uracil) • Original genetic Copy of the genetic Code code

  18. IV. DNA replication- DNA makes a copy of itself during interphaseof the cell cycle. • ***This occurs in the nucleus of the cell.

  19. Step 1- The double helix untwists and looks like a ladder. • The hydrogen bonds between the bases. • The two nucleotide chains begin to break and the chains open like a zipper.

  20. Step 2-Each chain serves as a pattern for the formation of a new chain of DNA. • Bases on the free nucleotides found in the nucleus, join with the correct bases according to the DNA code. • This type of replication is known as semi-conservitive.

  21. Step 3. -- bonds form between the phosphates and the sugars. • Step 4.--the two new molecules of DNA become twisted again.

  22. DNA Quiz: Copy the questions. • Describe the make up of DNA. • What is the bonding pattern of the bases? • What type of bond joins the bases? • What determines the genetic code? • Why does DNA go through replication?

  23. V. DNA Transcription The process of producing messenger RNA (mRNA) in the nucleus.

  24. STEP 1: The DNAmolecule carries the code to make a specificprotein. • The portion of DNA that contains the code for the specificprotein untwists and unzips.

  25. Free RNAnucleotides found in the nucleus pair with the exposed DNAstrand.

  26. http://www.johnkyrk.com/DNAreplication.html http://www.dnai.org/a/index.html

  27. The RNAcode is as follows: A – adenine joins with U – uracil C – cytosine joins with G – guanine

  28. A sequence of threebases on a mRNAmolecule that codes for an aminoacid is called a codon.

  29. The mRNA molecule is completed by the of formation of bonds between the RNA nucleotides. The mRNA molecule separates from the DNA molecule.

  30. The completed mRNA molecule leaves the nucleus through the nuclearmembrane and moves to the ribosome in the cytoplasm.

  31. DNA Transcription Quiz • What is being made in the process of transcription? • Give 2 ways RNA is different from DNA. • Where does transcription take place in the cell? • Write the complimentary DNA strand for the following: GTACCGGTAG • Write the RNA strand that would be made from this DNA: TACGGACTT

  32. VI. Translation: The assembly of a protein molecule according to the code in a mRNA which occurs in the cytoplasm.

  33. Step 1: One end of a mRNA molecule attaches to a ribosome.

  34. Step 2: Transfer RNA (tRNA) molecules in the cytoplasm pick up the amino acids. They are coded to correspond with a particular mRNA.

  35. tRNA

  36. Step 3: A tRNA molecule with the right anticodon links to the complimetary codon on the mRNA.

  37. Step 4: As the mRNA moves along the ribosome, the next tRNA comes in contact with the ribosome.

  38. The next tRNA moves in position with its amino acid which is linked together by peptide bond.

  39. Step 5: The first tRNA molecule is released and the next codon comes into place . Then the next amino acid is attached.

  40. ******Steps 3 – 5 Arerepeated until the entire message is translated. In this way chains of amino acids are formed. A protein molecule is built from one or more chains of amino acids. There are 20 essential amino acids in nature. • transcription tranlation • So: DNA ----→ mRNA ---- protein

  41. DNA Technology • Brought about a whole new science called molecular genetics scientists study DNA molecules and make changes in the DNA. • Led to a new field called genetic engineering.

  42. DNA extraction and Gel Electrophoresis • Technique used to separate the DNA from the rest of the cell is called DNA extraction.

  43. Long molecules of DNA can be cut into smaller pieces for study using special restriction enzymes.

  44. Pieces of DNA are called fragments and can be separated using gel electrophoresis.

  45. DNA fragment patterns can be used to compare the DNA of different organisms, to match the DNA of a specific organism, and to identify one certain gene out of the thousands of genes in the genome of one individual.

  46. Also called DNA fingerprinting because each person’s DNA is unique. • This procedure can be used to help prove or disprove a criminal’s identity, and it can also be used to show if two people are related to each other.

  47. Recombinant DNA • DNA extraction also makes possible something called recombinant DNA • Takes short pieces of DNA from one organism and joins it to the DNA of a completely different organism. • This can be placed back into a living cell by transformation.

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