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GeneralBiology
Molecular Genetics: DNA & Replication – Questions
History of DNA Matching
: Match each of the following with the appropriate scientist
a)
b) Avery et al.
c) Chargaff
d) Crick
e) Franklin
f) Griffith
g) Gurdon
h) Hammerling
i) Hershey & Chase
j) Miescher
k) Meselsohn & Stahl
l) Pauling
m) Saupe
n) Steward
o) Watson
p) Wilkins
1. _____ data provided evidence that DNA replication is semi-conservative
2. _____ determined DNA is rich with phosphorus
3. _____ female crystallographer
4. _____ first to observe that a transforming factor that could change bacterial strains
5. _____ nuclear transplant studies in algae showed that the nucleus contains the
genetic instructions
6. _____ nuclear transplant studies in toads demonstrated that a single nucleus
contains the genetic instructions to code for an entire organism
7. _____ showed that each plant cell has the genetic instructions to code for an
entire new plant
8. _____ studied Acetabularia
9. _____ studied nitrogenous base content of various species
10. _____ studied pus and sperm
11. _____ suggested that adenine paired with thymine, guanine with cytosine
12. _____ systematically digested components to determine the transforming factor was DNA
13. _____ tagged DNA with 32P
14. _____ tagged proteins with 35S
15. _____ used 15N to study DNA replication
16. _____ worked with bacteriophages
17. _____, _____ worked with virulent and avirulent strains of pneumonia bacteria (two answers)
18. _____ used a common kitchen appliance to help show that phage DNA carries instructions to make new phage particles.
19. _____, _____ data provided evidence that DNA is a helix (two answers)
20. _____, _____ data provided evidence that DNA is a uniform thickness (two answers)
21. _____, _____ determined the structure of DNA (two answers)
22. _____, _____ studied sugar coated bacteria (two answers)
23. _____, _____ used data from other scientists and built models (two answers)
24. _____ thought DNA was a triple-stranded molecule; American biochemist
25. _____ really cool; looks like Brad Pitt; has been offered several Nobel Prizes but was too modest to accept them; sheep rancher
Nucleic Acid Structure Questions
1) Explain how you know the molecule at the right is a nucleic acid.
2) Is this molecule DNA or RNA? How do you know?
3) Why are nucleic acids, ‘acids’? In other words, what makes them acidic?
4) Label the 3’ and 5’ ends of the molecule below.
5) Circle a single nucleotide and label the three components (sugar, phosphate, nitrogenous base)
6) How many nucleotides make up this nucleic acid?
7) Nucleic acids are always constructed 5’ to 3’. In other words, new nucleotides are always added to the 3’ end. Put a star showing where the next nucleotide will be added.
8) Thymine and cytosine are pyrimidine nitrogenous bases with a single ring. Thymine has two carbonyl functional groups on its ring system. Cytosine has a carbonyl and amino function group on its ring. Label these nitrogenous bases T and C, respectively.
9) Adenine and guanine are pure nitrogenous bases with two rings. Adenine has a single amino functional group on its rings while guanine has a carbonyl functional group and amino group. Label these nitrogenous bases A and G, respectively.
10) Examining the molecules and functional groups, explain why just two hydrogen bonds will form between A and T but three form between G and C.
Short Answers
:
1. How did Watson & Crick know that a triple helix model of DNA was incorrect?
This model was based on 3 strands with unionized phosphate groups in the middle holding the molecule together. This didn’t make sense because if the phosphate groups still had hydrogen’s, DNA would not be an acid…… which it is.
2. Explain why it would not have been possible for Watson and Crick to develop their DNA
model without the data from Franklin.
Franklin’s x-ray crystallography work provided info including:
1 – DNA’s phosphate groups are on the outside of the molecule;
2 – DNA could be helical structure; and DNA has a constant diameter along the length of the molecule.
3. What did Watson need to consider when he worked out the DNA base pairing?
Bond Angles, Bond lengths, the location of hydrogen atoms; and Chargaff’s pairs (although he didn’t realize it at the time).
More Short Answer
: Explain how the DNA molecule:
1. stores genetic information – DNA stores our genetic information used to build proteins. The specific base pairings code for specific amino acids these build these particular proteins. If you have the wrong base pairing, you will most likely get the wrong amino acid, and thus the wrong protein.
2. is copied –
3. can account for the diversity of life on the planet –
4. can account for the variability between species
5. can account for evolutionary changes that are driven by mutations – DNA mutations happen when there are changes in the nucleotide sequence that makes up the strand of DNA. This can be caused by random mistakes in DNA replication or even an environmental influence like UV rays or chemicals. The changes at the nucleotide level then influence the transcription and translation from gene to protein expression. Changing even just one nitrogen base in a sequence can change the amino acid that is expressed by that DNA codon which can lead to completely different protein being expressed. These mutations range from being non-harmful all the way up to causing death.
Replication Matching Question
:
a) DNA ligase
b) DNA polymerase I
c) DNA polymerase III
d) Helicase
e) Primase
f) Single-stranded binding protein
g) Topoisomerase
1. _____ binds and stabilizes single-stranded DNA
2. _____ links end of DNA that replaces primer to rest of strand
3. _____ makes RNA
4. _____ prevents unwound DNA from reannealing
5. _____ primary enzyme for making DNA
6. _____ relieves the strain in DNA as the molecule is unwound
7. _____ removes RNA nucleotides and replaces with DNA nucleotides
8. _____ synthesizes primer sequence
9. _____ unwinds DNA at the replication fork
10. Consider the molecules in the list (a – g) above. These molecules are:
a. All proteins
b. All nucleotides
c. Some are proteins and some are nucleotides
d. It’s impossible to determine
Replication:
The following represents the nucleotide sequence in the gene for a short polypeptide (protein). The strand shown is the template 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 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 template strand, the complementary (non-template) 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 template 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
General Biology
Molecular Genetics: Transcription & Translation Questions
Transcription/Translation
: Consider the gene below:
3
’
1
2
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
5’
A
T
G
G
G
A
A
T
T
G
G
T
T
A
C
T
C
A
T
A
A 3’
1. In the space below, write the nucleotide sequence for the mRNA encoded by the gene. Be sure to indicate the 3′ and 5′ ends for the mRNA.
2. Circle the translation start codon in the mRNA above.
3. 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.
4. What amino acid does the start codon specify? ________
5. Circle the translation stop codon in the mRNA strand above.
6. 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.
Mutations
:
1. Assume that there is a 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 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
2. This is an example of a(n) _______________ mutation.
a. point b. frame shift c. missense
3. Assume that there is a 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 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
4. This is an example of a(n) _______________ mutation.
b. point b. frame shift c. missense
5. 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
6. 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
7. Assume that you isolate the polypeptide that was made in question #4 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.
