| 4) Remembering that one human cell has 23 pairs of chromosomes, explain why it is very possible for the DNA in a single cell to contain the directions for all the inherited traits in an individual.
5) Do all organisms have the same base pairing in the DNA? 6) What separates one species from another according to its DNA? Activity #6: The DNA Molecule�s Two Functions The DNA molecule has 2 functions (write �em down!): 1) Heredity: The DNA molecule replicates itself so that the genetic information that it carries is passed onto the chromosomes of all future generations of cells. 2) Control of Cellular activities- The DNA molecule passes information on to the cytoplasm to direct the activities of the cell. All enzymes are proteins and genes control protein synthesis. Knowing this, explain why it would be correct to say that DNA controls all of the cell�s activities. Activity #7: How DNA Replicates Page 235 text The process of DNA cloning itself for new cells is called replication. Think! When would cells need to make copies of itself?! Here�s the cliff notes version on DNA Replication: 1) Starting at one end of the molecule, a �zipper� reaction begins. The weak H-bonds connecting the base pairs come apart like a zipper. a. What kinds of proteins unzip the DNA molecule? b. What�s to keep the DNA molecule from unwinding? 2) Each separation leaves an exposed base, which can take up a complimentary partner; a nucleotide containing an �A� must unite with one containing a �T� and so forth. As the DNA double helix separates, each half then forms a new upright to the ladder, identical to the one from which it separated. a. What enzyme attaches free nucleotides to the parent template? b. Look carefully at fig. 8.8 (pg237). A Japanese scientist named Okazaki discovered that nucleotide attachment differed according to which side of the DNA strand was being attached. What did he discover? c. Draw a picture of the DNA double helix unwinding and showing a continuous assembly, on one strand vs. a discontinuous assembly on the other strand. These discontinuous strands are called Okazaki Fragments. d. Which enzyme fills in tiny gaps between the new short Okazaki Fragments? 3) AS the �unzipping� proceeds along the molecule, a closing of new �zippers� follows behind. Where previously, there was one double ladder, there are now two. The two new DNA molecules are EXACT DUPLICATES of the original molecule. 4) Please answer the reviewing the main ideas questions 1-5 pg. 238. Activity #8: From DNA to Protein synthesis Introduction 1) What is the central dogma? 2) What�s transcription? 3) What�s translation? 4) Please copy down the little flow chart on the bottom of page 238, fig. 8.10. Activity #9: Transcription DNA carries the instructions for protein synthesis in the form of a code, which consists of the order of sequence of its nitrogen base pairs. Protein synthesis occurs in the ribosome. Since DNA can�t leave the nucleus, it passes the code by means of a process called transcription. In Transcription, a strand of DNA acts as a pattern for the manufacture of messenger RNA or mRNA. 1) Name 3 ways RNA is different from DNA in how transcription differs from DNA replication. 2) RNA consists of 4 types of nucleotides. What are they? Are they the same as DNA? 3) When does transcription begin? When would it end? 4) What is the final result of transcription? 5) What happens to the new mRNA in eukaryotic cells like us? What�s a pre-mRNA? 6) What�s the difference between introns and extrons? What�s so darn important about them? Once these new bases are assembled in order according to the DNA base code, they form the single stand messenger RNA molecule. It is then able to leave the nucleus of the cell and proceed to the ribosomes of the DNA molecule, which is served as the template, just zip back together again. 7) If the DNA strand looked like this: 5� GCCTAT 3� 3� CGGATA 5� What would the mRNA look like? Show this to Mr. Liao before you go on! |