DNA: STRUCTURE AND REPLICATION (Filmstrip)
Structure of DNA
- DNA stands for _____________________________________________
- DNA is an unusual molecule in that it:
- DNA is the primary material found in ____________________________________ (evidence suggests that a chromosome is a single coiled molecule of DNA)
- Humans possess (in their body/somatic cells) ______________ chromosomes. We inherit _______ chromosomes from our mother and ______ from our father.
- In eukaryotic cells, DNA molecules (chromosomes) are found in the ___________________.
- The 3-dimensional structure of DNA was discovered by ____________________ and ___________________.
- The shape of the DNA molecule is best described as a ____________________ ____________________ with ____________________ bonded to the ____________________.
- The building blocks of DNA are units called ______________________________. A nucleotide consists of 3 parts:
- Sketch and label a nucleotide below:
- There are 4 kinds of nucleotides in DNA:
- PURINE nucleotides include ____________________ and ____________________. PYRIMIDINE nucleotides include ____________________ and ____________________.
- Adenine always bonds with ____________________ and cytosine always bonds with ____________________. This is called "complementary base pairing".
- Sketch and label an unwound DNA fragment below.
- Sketch the chemical structure of the phosphate group.
- Sketch the chemical structure of deoxyribose sugar.
- How many rings are present in adenine and guanine (purines)? _______
How many rings are present in cytosine and thymine (pyrimidines)? ______
Replication of DNA (occurs during Interphase)
- Are the bonds between complementary bases weak or strong? _______________. What kind of chemical bond holds the strands together at the bases? ________________ bonds.
- DNA separates (unzips) between the ____________________ and the molecule may also unwind (ie. the _____________________ bonds are broken). The OLD strands are now separated. This step requires the enzyme ____________________.
- New ____________________ (which are floating around in the nucleus) are matched and bonded to complementary bases on the outer OLD strands to form inner NEW strands. This is called "complementary _____________ ___________________". This step requires the enzyme _________ ____________________ because new polymers (long strands of molecules) are being produced.
- Then the "backbone" (which consists of ____________________ and ____________________ molecules) is "zipped up" by the enzyme ____________________. In this step, each nucleotide in a new strand is joined to the one above and below it at the phosphates and sugars.
- Thus, ______ DNA molecules are produced from the original molecule. The DNA molecules make up the chromosomes which stay joined to eachother due to a ___________________________.
- The DNA molecules produced by DNA replication are ____________________ to each other.
- The replicated DNA molecules (chromosomes) are now ready to go into ______________________