DNA and
RNA
DNA
 Deoxyribonucleic acid (DNA)contains information on how to make
proteins. Proteins are the building blocks
of life.
 DNA is made up of: a sugar
(deoxyribose), a phosphate group
and four nitrogen bases.
 The 4 nitrogen bases are:
 Guanine (G), Cytosine (C), Thymine (T)
and Adenine (A).
 In DNA, Adenine and Thymine make up a
base pair, while Guanine and Cytosine
make up the other base pair.
 Together a phosphate group, a sugar and one
nitrogen base make up a NUCLEOTIDE.
Structure
 DNA is a double
stranded structure
referred to as a
double helix or
twisted ladder.
 DNA always turns
to the right.
 Nitrogen base pairs are
held together by
Hydrogen bonds*A=T, G=C*
Where is DNA found?
 DNA is found in the nucleus of cells,
and can be referred to as
chromatin.
RNA
 Like DNA, Ribonucleic acid is also
made up a sugar, phosphate group
and nitrogen bases. But there are
some major differences- The sugar in RNA, is Ribose.
 the nitrogen bases consist of Uracil
(U), Adenine, Guanine (G) and
Cytosine (C).
 Uracil and Adenine = Base Pair
 Guanine and Cytosine = Base Pair
 A nucleotide consist of a sugar, phosphate
group and one nitrogen base.
 Like DNA, the backbone of RNA is
composed of phosphates and sugars.
 RNA is single stranded.
Time for practice!
Practice Questions
Question from Fall 2005
TAKS Test
28. “Thymine-guanine-thymine-cytosine”
describes:
F. Nucleotides within an RNA strand
G. A sequence of bases within the DNA
section
H. Points of DNA separation during protein
synthesis
J. tRNA codons for specific amino acids
Answer!!!
 The answer is G!!!!
 Thymine, adenine, Guanine and Cytosine
are all nitrogen bases that can be found
in a DNA sequence.
Question from July 2004
33. All of the following are found in a DNA
molecule exceptA. carbon dioxide
B. deoxyribose
C. nitrogen
D. phosphate
Answer!!!
 The answer is A!!!
 A DNA molecule is made up of 3 main
parts. The Phosphate group, a nitrogen
base and a sugar (deoxyribose).
Together these 3 parts are called a
nucleotide.
Question from 2003 TAKS
test
24. If the template of a strand of DNA is
AGATGCATC, the complementary
strand will beF. TCTACGTAG
G. CTACGTAGA
H. AGATGCATC
J. AGACGTCTA
Answer!!!
 The answer is F!!!
 Adenine and Thymine pair up together
 Guanine and Cytosine pair up together
Question from April 2006
40. In all plant and animal cells, the nucleus
contains long molecules of DNA. Which of the
following best describes the function of DNA?
F. DNA provides the shape and structure of the
nucleus.
G. DNA packages materials for transport through
the nucleus.
H. DNA carries materials into and out of the
nucleus.
J. DNA contains the blueprint for producing the
whole organism.
Answer!!!
 The answer is J!!!
 DNA can be thought of as a blueprint, or
a set of instructions for building an
organism.
Question from April 2006
45. Erwin Chargaff studied the DNA of organisms
within a single species. Chargaff discovered
that the amount of adenine is about equal to the
amount of thymine. Which of these explains
why the ratio of adenine to thymine is nearly
1:1?
A. Adenine and Thymine pair with each other.
B. Adenine binds with phosphates, while thymine
binds with nitrates.
C. Adenine and thymine are identical in their
chemical composition.
D. Adenine bases contain a form of thymine.
Answer!!!!
 You guessed it! The answer is A!!!!!
 Remember, Adenine binds with thymine
and guanine binds with cytosine.
 Each base is its own chemical, they are
not like each other.