1. THE BUILDING OF A DNA MOLECULE

   Build a DNA molecule using the information in the computer program. Illustrate the molecule that you constructed below.
   example

2. DNA REPLICATION
   1. In a typical eukaryotic cell, what must happen before DNA replication can occur?
      The two parent strands must be separated, aided by enzymes

   2. When in the cell cycle does DNA replication occur?
      S subphase of interphase.

   3. What is happening to the chromatid number per chromosome of a eukaryotic cell as a consequence of DNA replication?
      Each chromosome has 2 sister chromatids after replication.

   4. p. 178 Copy the left strands of the original DNA sample by clicking on the appropriate base name. Each new DNA molecule consists of one parent strand and one newly synthesized strand. As each new DNA molecule is composed of one parent strand and one newly-synthesized strand, DNA replication is called semi-conservative replication.

   5. Why the need for DNA replication?
      The cell needs to replicate its DNA to prepare for cell division.

3. RNA STRUCTURE

   Draw a RNA nucleotide:
   example

   List 3 structural differences between DNA and RNA

   1. DNA has deoxyribose sugar, RNA has ribose
   2. DNA is usually double-stranded, RNA single-stranded
   3. DNA has Thymine, RNA has Uracil as one of its pyrimidines

4. TRANSCRIPTION OF THE DNA CODE
   5. What molecule does the DNA transcribe which will then be translated alongside the ribosome?
      mRNA

   6. Where is this molecule formed in a eukaryotic cell?
      Nucleus

   7. Where is this molecule found in a prokaryotic cell?
      Cytoplasm

   The enzyme RNA polymerase begins the transcription process by binding to the promoter site on the DNA molecule. Transcription begins when the hydrogen bonds break between the two DNA strands so that the strands can separate.
   

   p. 179 Copy the DNA code from the screen. As you transcribe the code, record the letters you are typing.

   Given DNA:	New mRNA:
   AGC	UCG
   TGG	ACC
   ACT	UGA
   ACG	UGC

   Choose the correct order for the steps of transcription listed.

   1. RNA polymerase binds to a specific site (the promoter) on the DNA.
   2. Hydrogen bonds between bases break allowing the DNA strands to separate.
   3. mRNA is transcribed from the sequence of bases on DNA (RNA and DNA nucleotides form base pairs).
   4. mRNA moves into the cytoplasm with its message.

5. POLYPEPTIDE SYNTHESIS - PART 1

   Show the bases of the mRNA strands on the screen. Record the corresponding amino acids below.

   Given mRNA:	Amino acid:
   UUA	LEU
   CCA	PRO
   CAC	HIS
   UGU	CYS
   UAG	STOP

   Next on the data sheet, provide the triplet code (codon) from mRNA that matches the given amino acid.

   Given amino acid:	mRNA codon:
   MET	AUG
   ALA	GCx
   LYS	AAA, AAG
   ASP	GAC, GAU
   GLU	GAA, GAG

   Translation takes place at structures in the cytoplasm called ribosomes.

6. POLYPEPTIDE SYNTHESIS - PART 2

   Draw and label a typical tRNA molecule.
   example

   8. p. 180 What part of the tRNA molecule determines where the tRNA attaches to the mRNA?
      anticodon

   9. What anticodon corresponds to the codon CUU?
      GAA
   For the mRNA given, record the base sequence and the tRNA anticodon that would correspond.

   mRNA:	tRNA:
   CUU	GAA
   AAG	UUC
   GCC	CCG
   UGU	ACA
   CUU	GAA
   GUC	CAG
   GCC	CGG

   You will be given the beginning of the DNA code for a gene that directs the production of the polypeptide covering for the HTLV-11 virus that causes a type of leukemia.

   1. Copy the DNA sequence below.
      ATG GGT AAT GTT TTC

   2. Transcribe the mRNA for the given DNA sequence and record it below.
      UAC CCA UUA CAA AAG

   3. Give the corresponding tRNA anticodon.
      AUG GGU AAU GUU UUC

   4. Give the corresponding sequence of amino acids.
      TRP PRO LEU GLN LYS

   List the 4 steps in building a polypeptide:

   1. Transcribe mRNA
   2. tRNAs carry amino acids to the mRNA
   3. mRNA associates with a ribosome
   4. amino acids form a chain (protein)
   10. When is the protein actually formed?
       When the polypeptide chain is released from the ribosome.

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