On the first few screens, you will build a small section of DNA. When your molecule is complete, draw it below.
example

1. During replication, what must happen first to the double-stranded DNA molecule?
   DNA replication begins when the two parent strands separate aided by enzymes which assist in breaking the bonds between complementary bases.

2. Copy the left strand of the original DNA sample by clicking on the appropriate base name.
   Because each new DNA molecule consists of one parent strand and one newly synthesized strand, DNA replication is called semiconservative replication.

3. The twisted shape of the DNA molecule is called double helix.

4. Explain why a cell needs to double the amount of DNA before it divides? Note - this answer is not given in the program.
   The cell needs to replicate its DNA before cell division so that each daughter cell has a full complement of DNA.

1. Draw an RNA nucleotide.
   example

2. p. 102 In what 3 ways does RNA differ from DNA?

1. DNA has deoxyribose sugar, RNA has ribose (with one more oxygen)
2. DNA is usually double-stranded, RNA single-stranded
3. DNA has Thymine, RNA has Uracil

1. What molecule does the DNA use to send its message to the cytoplasm where it will direct protein synthesis?
   mRNA

2. Where is the molecule above formed in a eukaryotic cell?
   mRNA is formed in the nucleus, then moves to cytoplasm.

3. The enzyme RNA polymerase begins the transcription process. This enzyme binds to the promoter site on the DNA molecule.

4. Transcription begins when the hydrogen bonds between the 2 DNA strands break so the strands can separate.

5. Copy the DNA code from the screen below. As you transcribe the code, record the letters you are typing.

   Template DNA:	Complementary mRNA:
   AGC	UCG
   TGG	ACC
   ACT	UGA
   ACG	UGC

   Choose the correct order for the steps of transcription listed. Make a list of these steps below.

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

1. On the screen after the genetic code table, record the the mRNA strand shown.
   Then using the chart shown, type in the 3 letter abbreviation for the amino acid that matches each codon and record the abbreviations below.

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

2. p. 103 On the next screen, type a mRNA codon that matches each given amino acid (there will be more than one possible correct codon for each amino acid).

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

3. Protein synthesis, also known as translation, takes place at structures in the cytoplasm called ribosomes.

1. Draw and label a typical tRNA molecule.
   example

2. What part of the tRNA molecule determines where the tRNA attaches to the mRNA?
   anticodon

3. What anticodon corresponds to the codon CUU?
   GAA

4. When you get to the screen with a piece of mRNA attached to a complete ribosome, record the base sequence of the mRNA and the tRNA anticodons that are complementary.

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

5. You will be given the beginning of the DNA code for a gene that directs the production of the protein covering for the HTLV-11 virus that causes a certain type of leukemia. Follow the prompts to answer the following:
   1. Copy the DNA sequence given below.
      ATG GGT AAT GTT TTC

   2. Transcribe the mRNA for the given DNA sequence and record it below. p. 104
      UAC CCA UUA CAA AAG

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

   4. Give the corresponding sequence of amino acids.
      Trp(should be Tyr) Pro Leu Gln Lys
      (See codon table)

6. List the 4 steps in building a protein.
   1. Transcribe mRNA
   2. mRNA associates with a ribosome
   3. tRNAs carry amino acids to the mRNA
   4. Amino acids form a chain (protein)

A mutation in this DNA sequence
CTG ACA TAC GGC GGT yields this new sequence:
CTG ACA ACT ACG GCG GT

1. What type of mutation occurred?
   
   1. Point
   2. Addition
   3. Deletion
   (Answer: B)

2. How did the mutation affect the amino acid sequence?
   
   1. Missense - the substitution of one amino acid for another
   2. A large alteration of the amino acid sequence
   3. Nonsense - premature termination of the amino acid sequence
   4. No change - a base change that does not affect the amino acid sequence
   (Answer: C)
   (See codon table)
   The mutated DNA sequence ACT transcribes to the triplet UGA on the mRNA, which is a STOP codon.)

The amino acids of a protein are linked together by a process called dehydration synthesis. The acid group of one amino acid bonds to the amino group of the next, forming a peptide bond and releasing a molecule of water.

Wool is a protein with alpha helix secondary structure, giving it flexibility and elasticity.

Silk is a protein fiber with beta sheet secondary structure, containing at least four amino acids linked together by hydrogen bonds.

A beta bend allows an amino acid chain to reverse direction by folding back on itself, producing a hairpin turn.

Some amino acid sequences in a protein do not have a structure and take on a random form.

Choose one of these genes:

• Short Gene- Somatostatin
• Long Gene - Glucagon
• Custom Gene - Enter up to 105 bases

Perform each of these mutations: (within the promoter TATAATG, or 25-30 bases after the promoter)

• Point
• Addition
• Deletion