Download 01/19/2017 Worksheet - Iowa State University

DNA Structure and the
proteins that bind to it
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Matt C.
Biol/Gen 313
Dr. Myers & Dr. Vollbrecht
01/19/2017
Introduction: This worksheet discusses material covered in the third lecture (01/13/17). Chapter
8 examines these topics.
Concepts
1. DNA Structure.
2. Proteins that associate with DNA.
Material
1. DNA Structure
In this section, we’ll be reviewing the chemical structure of nucleotides and the bonding
patterns that lead to double-stranded DNA polymers. Some of this is review from the
previous worksheet as well.
1. Describe the difference between a purine and a pyrimidine.
2. Describe how purines and pyrimidines are similar.
3. What is the difference in hydrogen-bonding between the cytosine-guanine pair and
between the adenine-thymine/uracil pair? Why does this difference occur?
4. Name which base(s) will pair with the base pictured below.
a.
1060 Hixson-Lied Student Success Center  515-294-6624  [email protected]  http://www.si.iastate.edu
b.
c.
d.
5. How will you differentiate between an RNA nucleotide and a DNA nucleotide?
6. Sketch a model of two DNA nucleotides in separate nucleic acid polymers that are
associating to form a double-stranded DNA molecule. Draw the sugars of these two
nucleotides specifically and indicate directionality. The nitrogenous base doesn’t have
to be specific, but choose two bases that would pair in DNA and indicate the number
of hydrogen bonds between them. Specifically draw phosphodiester bonding.
7. Describe an example of RNA secondary structure. Draw a simple diagram.
2. Proteins that associate with DNA
Chromosomes and chromatin are made up of much more than just DNA. This section
will look into how proteins interact with DNA in chromosomes or chromatin.
1. How do proteins that need to identify specific sequences find those sequences in
the DNA molecule?
2. Describe briefly the “beads on a string” idea as it relates to chromatin.
3. How do histones bind to DNA?
4. In an isolated strand of chromatin, you find 12 molecules of histone H3. How
much of the following would you also expect to find?
a. Histone H1
b. Histone H2A
c. Histone H4
d. Nucleosomes
e. Base pairs of DNA wrapped around histone complexes.
f. Base pairs in total (give a rough estimate and explain why).
5. How would you limit how tightly histones bind to their DNA?
6. Describe examples of heterochromatin and euchromatin. Why are each of these
helpful in their own way? (These are from the reading.)
7. What’s the best way to identify centromeric regions in chromatin? (Very
specifically from the reading.)
8. Why do telomeres exist? How do they do their job?
Things to do next
 Focus your review on things that were difficult from this worksheet. If it was really
challenging, don’t worry; these are meant to be tough and push your understanding of the
topics we covered.
 There are a few topics in Chapter 8 that this review didn’t go into, namely the types of
eukaryotic DNA. Things that were skipped weren’t discussed in class, but since they’re
in the reading, it’s still possible that they will show up on exams. If you read through the
sections I skipped over and aren’t sure what they’re getting at, feel free to email me.
 If you have any questions, ask me in session, in class, or by email. I’m more than happy
to help.
 Next session (Sunday 01/22/17) we’ll be talking about any material not completed from
this worksheet and about material from the fourth lecture (01/18/17). The fourth lecture
discussed the first parts of DNA replication.