
Deoxyribonucleic Acid

2. What are the repeating subunits called that make up DNA?

Nucleotides

3. Sketch and label the 3 parts of a
DNA nucleotide.

Include a phosphate, deoxyribose sugar, and nitrogenous base

4. Name the 4 nitrogen bases on DNA
(spelled out – spelling counts on the test).




Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

5. What scientists made the first ever model of DNA as a double helix?

James Watson and Francis Crick

6. What is Chargaff’s rule?


Chargaff found that for a particular species, the concentration of adenine is roughly equal to the concentration of thymine (A=T) and cytosine is roughly equal to guanine
(G=C)
This helped found the base pair rule, that A always pairs with T, and
C always pairs with G



Since A = T,
A. Thymine = 36% (roughly)
To figure out C and G, subtract from 100%
100 – 36 – 36 = 28, then divide equally into
C and G


B. Cytosine = 14%
C. Guanine = 14%
*Be prepared to do problems without a calculator on the test

7. How did Rosalind Franklin contribute to determining the structure of DNA?

She produced an X-Ray diffraction photo that showed DNA’s structure.

8. What makes up the sides of a DNA molecule?

Sugar (deoxyribose) & Phosphate

9. What makes up the “steps” of a
DNA molecule?

The nitrogenous bases (A,T,G,C)

10. What type of bonds hold the DNA bases together? Are they strong or weak bonds?

Weak hydrogen bonds

11. What type of bonds hold the
"backbone" of the DNA molecule together?

Covalent bonds join sugar & phosphate

12. Name the complementary base pairs in DNA.


Adenine – Thymine
Guanine - Cytosine

13. Why must DNA be able to copy itself?


DNA must be copied in order for a cell to divide
Transmit information for traits to the next generation

14. Define semi-conservative replication.
(in DNA coloring packet!)


DNA saves or conserves 1 strand to produce 1 new strand
Produces 2 identical doublestranded DNA molecules, each containing 1
“original” strand, and 1 “new” strand

15. What is the first step that must occur in DNA replication?

Separating of the two strands of
DNA by breaking the hydrogen bonds


The place where DNA separates in order to be copied.

17. What are the functions of DNA polymerase?


DNA polymerases add nucleotides to new DNA strands
DNA polymerase also proofreads the strands for errors

18. Why aren’t many genes located on the tips, or telomeres, of chromosomes? What does telomerase do to help with this?


Telomeres are susceptible to damage, and thus don’t contain many genes
Telomerase is an enzyme that adds short, repeated nucleotides to the ends so that if damage occurs, the chromosomes are not affected, since the sequences don’t contain genes

19. If the sequence of nucleotides on the original
DNA strand was A-G-G-C-T-A, what would be the nucleotide sequence on the complementary strand of
DNA?

TCCGAT

20. Does replication of DNA begin at one end and proceed to the other? Explain.

No, it can begin at many places, and proceeds in opposite directions until the entire sequence has been replicated

21. Why does DNA replication take place at many places on the molecule simultaneously?

To replicate (copy) the DNA quicker.


Before cell division (interphase – S phase = DNA synthesis, which is the another way of saying DNA replication)

23. Sketch & label DNA replication.

24. Give 3 differences between prokaryotic and eukaryotic replication:



Prokaryotic replication involves circular DNA (vs. double helix)
Prokaryotic replication takes place in the cytoplasm (vs. nucleus)
Prokaryotic replication has 1 origin
(vs. many origins for eukaryotic replication)