The mortal, living-and-dying individual is the transient
care-taker of the instructions that must be conveyed down the
generations...An individual life has significance only to the extent
that it passes information about its ancestors to its descendents.
M. Hoagland |
Required Reading:
text, Chapter 11, 12, 13, 14
Goal of the Unit:
The goal of this unit is to provide an introduction to the field of molecular
genetics. Our studies will focus on the structure of RNA and DNA, replication,
and how genes specify phenotype.
Important Terms/Concepts
- Replication:
(can you use them in a conversation? or make a concept map? or crossword
puzzle? or write an essay using them?)
|
-
leading strand
-
lagging strand
-
ligase
-
primase
|
|
Important Terms/Concepts
- Transcription
|
-
promoter
-
ribozyme
-
RNA
-
RNA
polymerase
|
|
Important Terms/Concepts
- Translation
-
codon
-
anticodon
-
�redundant� code
-
unambiguous code
-
intron
-
exon
-
spliceosome
-
leader sequence
|
|
|
Important Terms/Concepts
- DNA Structure
-
3', 5'
-
adenine
-
antiparallel
-
complementarity
-
cytosine
-
deoxyribose
-
DNA ligase
|
-
gene
-
guanine
-
helix
-
hydrogen bonds
-
nitrogenous base
-
nucleotide
|
-
purine
-
pyrimidine
-
ribose
-
thymine
-
uracil
|
Learning
Objectives:
Upon completion of this unit you should be able to:
-
Explain how the structure of DNA molecule: (a) stores information, (b) allows for variability
and diversity; (c) allows for mutability (mutation); and (d) allow for exact replication.
-
Describe Hammerling�s experiments with Acetabularia and explain how
these experiments, and those of Gurdon and Steward, demonstrated that the
nucleus was the site of the genetic instructions in eukaryotic cells.
-
Explain why biologists earlier in the century believed that protein, but not
DNA, is the molecule of inheritance.
-
Describe Griffith�s experiments. What conclusions did he derive?
-
Describe the experiments/contributions of each of the following: Rosalind
Franklin, Griffith; Chargaff; Avery et al.; Hershey & Chase; Beadle & Tatum;
Watson & Crick
-
Describe the structure of DNA
-
Explain what a gene is, molecularly speaking, and explain why there is an
infinite number of possible genes
-
Suggest reasons why Avery's conclusion that DNA, not protein, carried the
genetic message, was not immediately accepted by biologists.
-
Answer the questions at the end of the chapter and on-line (course web site)
Matching: Match each of the following with the
appropriate scientist
a. Avery et al. b. Chargaff c. Crick d. Franklin e. Griffith |
f. Gurdon g. Hammerling h. Hershey & Chase i. Miescher
j. Meselsohn & Stahl |
k. Saupe l. Steward m. Watson n. Wilkins |
- _____ data provided evidence that DNA is a uniform
thickness
- _____ determined DNA is rich with phosphorus
- _____ determined the structure of DNA
- _____ female
- _____ first to identify a transforming factor that could
change bacterial strains
- _____ nuclear transplant studies in algae showed that
the nucleus contains the genetic instructions
- _____ nuclear transplant studies in toads demonstrated
that a single nucleus contains the genetic instructions to code for an entire
organism
- _____ really cool; looks like Brad Pitt; has been
offered several Nobel Prizes but was too modest to accept them; sheep rancher
- _____ showed that each plant cell has the genetic
instructions to code for an entire new plant
- _____ studied Acetabularia
- _____ studied nitrogenous base content of various
species
- _____ used 15N to study DNA replication
- _____ studied pus and sperm
- _____ studied sugar coated bacteria
- _____ suggested that adenine paired with thymine,
guanine with cytosine
- _____ systematically digested components to determine
the transforming factor was DNA
- _____ used data from other scientists and built models
- _____ worked with virulent and avirulent strains of
pneumonia bacteria
- _____ x-ray crystallographer
- _____ data provided evidence that DNA is a helix
- _____ data provided evidence that DNA replication is
semi-conservative
- _____ worked with bacteriophages
- _____ tagged proteins with 35S
- _____ tagged DNA with 32P
- _____ demonstrated that DNA is replicated semi-conservatively
A Replication/Transcription/Translation Question
The following represents the nucleotide sequence in
the gene for a short polypeptide (protein). The strand shown is the template
(or "sense") strand.
3� |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
5� |
|
T |
A |
C |
C |
C |
T |
T |
A |
A |
C |
C |
A |
A |
T |
G |
A |
G |
T |
A |
T |
T |
|
1. Replication: Beneath the template (sense) strand above, write the
nucleotide sequence for the non-template (anti-sense) strand of this segment of
DNA. Be sure to include the designation for the 3� and 5� ends.
2. During replication of the sense strand, the anti-sense
strand would be made from the:
a. right to the left
b. left to the right
3. If the DNA polymerase/replication fork moves along
the DNA from the LEFT to the RIGHT replicating the DNA, the new complementary
strand is made in:
a. one long piece
b. a series of short fragments c.
impossible to determine from the info provided
4. In the space below, write the nucleotide sequence for
the mRNA encoded by this gene. Be sure to indicate the 3' and 5' ends for
the mRNA.
5. Circle the translation start codon in the mRNA in #4
above.
6. What is the nucleotide sequence in the anti-codon loop
of tRNA that is complementary to the start codon? ______. Indicate the 3'
and 5' side of the anti-codon region.
7. What amino acid does the start codon specify? ________
8. Circle the translation stop codon in the mRNA strand in
#4 above.
9. Using a codon table (see table in your text), in the
space below write the predicted sequence of amino acids for the polypeptide
encoded by this gene.
10. Point Mutations - Assume that there is a point
mutation in the DNA in nucleotide 6
and it is changed from T, which occurs in the original strand, to
A as shown. In the space below,
write the amino acid sequence of the polypeptide that would result. How
will this mutation would this affect the final protein?
3� |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
5� |
|
T |
A |
C |
C |
C |
A |
T |
A |
A |
C |
C |
A |
A |
T |
G |
A |
G |
T |
A |
T |
T |
|
11. More Point Mutations - Assume that there is a point
mutation in the DNA in nucleotide 15 (red)
and it is changed from G, which occurs in the original strand, to
C as shown. In the space below,
write the amino acid sequence of the polypeptide that would result. How
will the mutation would this affect the final protein?
3� |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
5� |
|
T |
A |
C |
C |
C |
A |
T |
A |
A |
C |
C |
A |
A |
T |
C |
A |
G |
T |
A |
T |
T |
|
12. Insertions. Assume that two nucleotides, T and G
are inserted in the original DNA strand between nucleotides 4 and 5. How
will this affect the polypeptide? Write the sequence of amino acids in
the protein below.
3� |
1 |
2 |
3 |
4 |
|
|
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
5� |
|
T |
A |
C |
C |
T |
G |
C |
T |
T |
A |
A |
C |
C |
A |
A |
T |
G |
A |
G |
T |
A |
T |
T |
|
13. Which one of the following would be likely to
have the least impact on the final protein? (Explain)
a. an insertion involving one nucleotide
b. an insertion involving two nucleotides
c. an insertion involving three nucleotides
14. Assume that you isolate the polypeptide that was
made in question # above from a piece of �chicken-fried cat.� To your surprise
the protein begins with glycine! What�s the deal?
a. the DNA, like a sleazy cat, lied
b. a methionine amino acid was probably clipped off the
protein after translation
c. RNA polymerase made a mistake and inserted an incorrect
nucleotide.