WORKSHEET: INTRODUCTION TO MOLECULAR BIOLOGY

1. The new field of molecular biology emphasizes several older branches of science. Give one        example of an older branch of science, for each of the following categories, that is now blended        into molecular biology.
       A: chemistry ……………. B: biology ……………….. C: microbiology ……………..

2. Match each scientist below to the important scientific discovery about genetics they
       participated in.
       A: Darwin/Wallace 1: discovered the molecular double-helix structure of DNA
       B: Sutton/Morgan/McClintock 2: studied chromosome behaviors within cells //ex: meiosis
       C: Avery/Hershey 3: studied how DNA interacts within cells // ex: bacteria
       D: Watson & Crick 4: studied how traits are inherited by individuals // ex: peas
       E: Mendel 5: studied changes found in populations // called variations

3. The structure of DNA took many years of research to discover because of its unique structure.
       A: In some ways DNA seems simple in structure. Its molecular structure is simply composed
               of repeating subunits called (A)…………… . In the case of DNA this repeating subunit is               called a nucleotide, and is composed of 3 parts called (B)………………… bases,               (C)…………….. groups, and a 5C (D)……………. . To complete this simple pattern it was               discovered that the entire molecule looks like a twisted (E)…………..……….., with the               sides composed of alternating (F)……………….. and (G)…………….. molecules, and the               rungs (steps) composed of 4 types of (H)………………………. .
       B: As our knowledge of the DNA molecule increased scientists have discovered that DNA has               several quite unique features. One feature is that the molecules are precisely organized so               that a double-ringed atom called a (A)…………… is always paired with a single- ringed               atom called a (B)……………….. . Another surprising feature is that the DNA molecule is               weakest down its middle where it is held together by weak (C)…………….. bonds.
              Because DNA molecules tend to break apart down the middle, scientists say that DNA               looks like it is (D)……………. whenever it opens. Today scientist know that because of
               the precise structure of DNA the nitrogen base Adenine can only bond with (E)…………..,               while the base cytosine can only bond with (F)…………….. .

4. The unique structure of DNA helps it complete two vital functions: the production of (A)…………….        and control of all the cells (B)………………. . Since both of these functions are vital to the life
        of every cell the DNA must be duplicated in a process called (C)…………….. and one copy
        of the DNA must migrate into each new cell. This process of duplication involves several
        steps. First the DNA is unzipped with the aid of an enzyme called (D)……………………. .
        Next a new strand of DNA, called a (E)………………. strand forms using free nucleotides        floating in the cytoplasm of the cell. Finally new sugar-phosphate bonds are formed with the
       aid of an enzyme called (F)…………………….. . Unfortunately this process is not perfect
       and errors do occur at the rate of (G)……………………… .

5. To control all the cells activities DNA must produce proteins. To produce proteins DNA must use
        a second group of molecules called RNA. RNA differs from DNA in that it only has (A)………        strand of monomers, its 5C sugar is called (B)………….., and it uses the nitrogen base called        (C)…………… rather than (D)………… . These differences allow RNA to do several jobs DNA        cannot. For example mRNA, also called (E)……………RNA, transmits information from the        (F)…………. in the nucleus to (G)………….. in the cytoplasm. tRNA. also
       called (H)…………RNA can bind to a specific (I)……………….. and carry it to where it is
       needed. rRNA, also called (J)……………..RNA is a major component of (K)……………. .

6. To begin the process of protein production the DNA code is copied into mRNA code in a
        process of (A)………………… . When the information in the DNA is encoded as mRNA it is        referred to as the (B)…………..code. This code consists of a specific group of 3 sequential        bases called (C)………….. . Each of these sequences of bases attracts a group
       of (D) …………… bases. Some codons don't code for amino acids, but instead serve to tell the        ribosomes to (E)………. or (F)………….. reading the mRNA. The tRNA's use bases called        (G)……………… that are complimentary to the codons of the mRNA to line themselves in the        right order along the mRNA. Finally the amino acids bond together to form a (H)………… .
       This entire process of making the mRNA, which then attract the tRNA's, which then line up
       the amino acids, is called (I)…………………… .

7. All 3 RNA's play a vital role in the production of proteins by the cell. Still each RNA has a unique        structure and completes a unique role in protein production. State whether each of the
       following descriptions applies to mRNA, OR tRNA, OR rRNA OR a combination of each.
       A: Is found in the cell cytoplasm.
       B: Is a single strand copied directly from DNA
       C: Is thought to be an ingredient of ribosomes
       D: Is destroyed after completing its task
       E: Contains codons
       F: Contains Uracil in place of Thymine
       G: Has at least as many different forms as there are types of amino acids.

8. What vital role do each of the following provide during protein synthesis?
       A: mRNA in transcription?
       B: tRNA in translation?
       C: ribosomes in translation?

9. Imagine that a DNA strand carries the code "GGC TAG GTC AAT".
        Let's follow it through the process of protein synthesis.
              beginning DNA ->          GGC TAG GTC AAT
              copied into mRNA->      CCG AUC CAG UUA
              attracts tRNA ->            GGC UAG GUC AAU
              lines up amino acids ->  Pro    Ile    Gln   Leu

     Now imagine that a second strand of DNA code is -> "ATC GAC TAG CAT".
     A: List the mRNA codons that will form from it.
     B: List the tRNA anticodons that will pair with the codons in "A".
     C: How many amino acids are coded by this strand of DNA? LIST THEM.
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CRITICAL THINKING:
10. A: What does it mean to say DNA is "universal"?
     B: What does it mean to say that DNA replication is semi-conservative?
     C: Use the idea of semi-conservatism to explain the following statement.
                "DNA never dies, but is as old as the oldest living organism."

11. Use the following data to answer the question below.
     - Mutations occur at a rate of 3 per 3 billion bases copied during replication.
          (Since there are 3 billion bases in one entire copy of the human genome, you could say that           equals 3 mutations after all DNA in one cell has replicated once.)
     - The human body, on average, consists of 3 trillion cells.
     - The DNA in a human cell must undergo replication, on average, every 3 months
       A: How many mutations will occur, on average, in a human body in one year?
       B: List 4 common causes of these mutations.
       C: Why haven't all these mutations rendered the DNA useless?

12. From where can the raw materials be located for each of the following processes?
       A: nitrogen bases for transcription?
       B: new sugars and phosphates for the new "rungs" during replication?
       C: new amino acids for translation?

13. The UV radiation produced by the sun is a major source of mutations in DNA. During the recent        history of our earth a layer of ozone gas has developed that blocks most of this UV radiation.
       A: How did the earliest life forms survive on earth without any ozone layer?
       B: What effect might the reduction of the present ozone layer have on simple animals?               ............... on humans?