DNA and Genetics


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DNA and Genetics

  1. 1. DNAand Genetics
  2. 2. The Structure of DNA Chromosomes are made of proteins and deoxyribonucleic acid, or DNA. DNA is an organism’s genetic material. A gene is a segment of DNA on a chromosome. Strands of DNA in a chromosome are tightly coiled, like a coiled spring. This coiling makes it possible for more genes to fit in a small space.
  3. 3. The Structure of DNA
  4. 4. A Complex Molecule The shape of DNA is like a twisted ladder. It is called a double helix.
  5. 5. A Complex Molecule Rosalind Franklin discovered that DNA is 2 chains of molecules in a spiral form.
  6. 6. A Complex Molecule Watson and Crick further studied the DNA model.
  7. 7. A Complex Molecule Watson and Crick discovered that each side of the ladder is make of a sugar-phosphate molecule.
  8. 8. A Complex Molecule
  9. 9. 4 Nucleotides shape DNA DNA has a twisted-ladder shape that is caused by molecules called nucleotides. A nucleotide is a molecule made of a nitrogen base, a sugar, and a phosphate group.
  10. 10. 4 Nucleotides shape DNA Sugar-phosphate groups form the sides of the DNA ladder. The nitrogen bases bond and form the rungs of the ladder.
  11. 11. 4 Nucleotides shape DNA Cells contain DNA in chromosomes. So, every time a cell divides, all chromosomes must be copied for the new cell. The new DNA is identical to existing DNA. Replication is the process of copying a DNA molecule to make another DNA molecule.
  12. 12. 4 Nucleotides shape DNA In the first part of replication, the strands separate in many places and the nitrogen bases are exposed.
  13. 13. 4 Nucleotides shape DNA Nucleotides move into place and form new nitrogen base pairs. This produces two identical strands of DNA.
  14. 14. 4 Nucleotides shape DNA
  15. 15. 4 Nucleotides shape DNA
  16. 16. ? Junk DNA All genes are segments of DNA on a chromosome. However, about 97 percent of DNA on human chromosomes is not part of any gene. Segments of DNA that are not parts of genes are often called junk DNA. It is not known whether junk DNA has functions that are important to cells.
  17. 17. Junk DNA http://en.wikipedia.org/wiki/Noncoding_DNA http://en.wikipedia.org/wiki/Noncoding_DNA
  18. 18. Junk DNA http://www.icr.org/article/3396/
  19. 19. Junk DNA
  20. 20. Junk DNA http://www.discovery.org/a/9941
  21. 21. The Role of RNA in making proteins Proteins are made with the help of ribonucleic acid. Ribonucleic acid (RNA) is a type of nucleic acid that carries the code for making proteins from the nucleus to the cytoplasm. RNA also carries amino acids around inside a cell and forms a part of ribosomes.
  22. 22. The Role of RNA in making proteins RNA, like DNA, is made of nucleotides. But RNA is single stranded, while DNA is doublestranded. RNA has the nitrogen base uracil (U), while DNA has thymine (T).
  23. 23. The Role of RNA in making proteins The first step in making a protein is to make mRNA from DNA. The process of making mRNA from DNA is called transcription. During transcription, mRNA nucleotides pair up with DNA nucleotides. Completed mRNA can move into the cytoplasm.
  24. 24. The Role of RNA in making proteins An enzyme splits a DNA molecule, so that a gene can be copied. The gene is the instructions for how to make a protein.
  25. 25. The Role of RNA in making proteins The free floating nitrogen bases in the nucleus match with a nitrogen base on the split DNA.
  26. 26. The Role of RNA in making proteins The partnering is the same as when DNA is copied except that Adenine matches with Uracil.
  27. 27. The Role of RNA in making proteins The nitrogen bases pair up on the split DNA temporarily until a complete gene is copied.
  28. 28. The Role of RNA in making proteins The newly made mRNA will now detach from the DNA and leave the nucleus.
  29. 29. 3 Types of RNA The three types of RNA are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). They work together to make proteins. The process of making a protein from RNA is called translation.
  30. 30. 3 Types of RNA messenger RNA mRNA
  31. 31. 3 Types of RNA ribosomal RNA rRNA
  32. 32. 3 Types of RNA transfer RNA tRNA
  33. 33. Translating the RNA Code Making a protein from mRNA is like using a secret code. Proteins are made of amino acids. The order of the nitrogen bases in mRNA determines the order of the amino acids in a protein. Three nitrogen bases on mRNA form the code for one amino acid.
  34. 34. Translating the RNA Code Each series of three nitrogen bases on mRNA is called a codon.
  35. 35. Translating the RNA Code There are 64 codons, but only 20 amino acids.
  36. 36. Translating the RNA Code Some of the codons code for the same amino acid.
  37. 37. Translating the RNA Code One of the codons codes for an amino acid that is the beginning of a protein. This codon signals that translation should start.
  38. 38. Translating the RNA Code Three of the codons do not code for any amino acid. Instead, they code for the end of a protein. They signal that translation should stop.
  39. 39. Translating the RNA Code
  40. 40. 3 Types of RNA 3 nitrogen bases on mRNA Another temporarily tRNA bonds. match to 3 bases on the tRNA. The amino acids that are attached to the tRNA bond, beginning to form the protein.
  41. 41. Translating the RNA Code
  42. 42. Mutations A change in the nucleotide sequence of a gene is called a mutation. Sometimes, mistakes happen during replication. Most mistakes are corrected before replication is finished. An uncorrected mistake can result in a mutation. Mutations can be caused by exposure to Xrays, ultraviolet light, radioactive materials, and some kinds of chemicals.
  43. 43. Types of Mutations There are several types of DNA mutations. In a deletion mutation, one or more nitrogen bases are left out of the DNA sequence. In an insertion mutation, one or more nitrogen bases are added to the DNA. In a substitution mutation, one nitrogen base is replaced by a different nitrogen base.
  44. 44. Types of Mutations
  45. 45. Types of Mutations Each type of mutation changes the sequence of nitrogen base pairs. A change can cause a mutated gene to code for a protein that is different from a normal gene. Some mutated genes do not code for any protein. For example, a cell might lose the ability to make one of the proteins it needs.
  46. 46. Results of a Mutation The effects of a mutation depend on where in the DNA sequence the mutation happens and the type of mutation. Proteins express traits. Because mutations can change proteins, they can cause traits to change. Some mutations in human DNA cause genetic disorders.
  47. 47. Results of a Mutation
  48. 48. Results of a Mutation With more research, scientists hope to find cures and treatments for genetic disorders. Not all mutations have negative effects. Some mutations do not change proteins, so they do not affect traits. Other mutations can cause a trait to change in a way that benefits an organism.