Study Guide
BIO 151/MED
CH 16: Molecular Basis of Inheritance
Name:
Directions: Read entire chapter. As you read, complete the questions below.
Overview 16.1
After the work of Mendel, Sutton, Morgan & Bridges, scientists were certain that
Mendel’s “factors” (genes) were physically located on chromosomes. Problem:
chromosomes consist of a single incredibly long DNA “ ladder” wrapped upon protein
“scaffolding”.
What organic molecule represented the genetic material: DNA or protein? The
race for certainty on this issue and to decode the code of life were on…….
1. In the early 20th century, why did most scientists believe that protein molecules held
the genetic code of life?
2. Define:
pathogenic transformation 3. Explain the significance of the “S” and “R” designations of strains of Streptococcus
bacteria:
4. Use this chart to summarize Griffith’s experiment:
Experiment
Bacteria
Living S bacteria
1
Living R bacteria
2
Heat-killed S
3
Dead S + Live R
4
5. What did Griffith conclude?
Mouse: Live or Die?
6. Avery methodically investigated possibilities for Griffith’s “transforming factors”.
A. What molecules did he study?
B. What did he conclude was the transforming agent which reprogrammed the
usually harmless “R-strain” cells?
C. Why were his finding largely ignored?
7. In the Hershey-Chase experiment,
 radioactive P was incorporated into which molecule?
 radioactive S was incorporated into which molecule?
8. When did the radioactivity enter the bacteria cells/pellets?
9. List two observations which Chargaff made about DNA:


10. List several scientists who were racing to determine the structure of DNA:
11. List 3-4 critical pieces of information which Watson gleaned from Franklin’s data.
(w/o her knowledge or consent!)
12. In the Watson-Crick model of DNA structure, how is the simplicity of structure of
DNA “overcome” to code for such a diversity of genetic traits?
Recommended Questions:
p. 310 (CC) #1,2
Sec 16.2: Read all. Use the questions below as a guide as you read along.
1. Which model of DNA replication did Watson & Crick suggest? Why?
2. The genome of E. coli bacterium is about ________________base pairs.
3. The human genome consists of approximately ______________base pairs.
4. The mutation rate in humans due to errors in DNA replication is
5. Compare and contrast DNA replication in prokaryotic and eukaryotic cells. List at
least 2 similarities and three differences.
6. What provides the energy necessary for DNA synthesis?
7. What is the role of each of these enzymes in DNA replication?
 helicases
 topoisomerase
 primase
 DNA polymerase III
 DNA polymerase I
 ligase
 nuclease
 telomerase
8. Be able to identify/describe each of the following as they pertain to DNA replication:
 origin of replication
 replication fork
 single-strand binding proteins
 leading strand
 lagging strand
 Okazaki fragments
 telomeres
 TTAGGG
9. What role do DNA polymerases perform in addition to adding free nucleotide to a 3’ end?
10. What else can cause a complementary pair “mismatch”, and therefore a genetic
mutation besides a matching “mistake” by DNA polymerase?
11. How many different DNA repair enzymes have evolved?
12. Why do chromosomes tend to shorten with every replication in eukaryotic cells but
not prokaryotic cells?
13. What prevents chromosomes from shortening in germ cells?
Recommended Questions:
p. 319 (CC) 1,2,3
sec 16.3
1. In humans, what is the size (in base pairs) of a typical chromosome? How does this
number compare to the human genome?
2. What type of protein molecules provide “scaffolding” for the DNA molecule of a
condensed chromosome?
3. How many histone molecules exist in one nucleosome?
4. Distinguish between euchromatin and heterochromatin.
5. If you examined one of your cheek cells in interphase, do you thing that most of the
DNA would exist as euchromatin or heterochromatin? Explain.
Recommended Questions:
p. 323 (CC) 1,2
Chapter Recommended Questions:
p. 324 (SQ) 1,3,5,6,8