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Human Anatomy
Lecture 2B (more information about what’s going on inside the cell)
Structure of DNA
What’s a protein?
 It’s a __________________ made of large molecules
 It’s an essential part of all living organisms, especially as _________________
components of body tissues, such as hair, muscle, collagen, etc.
 Proteins may act as enzymes and antibodies
____________________ do most of the work in cells, and they are required for the
structure, function, and regulation of the body’s tissues and organs
The instructions for making a protein are found within _____________
DNA is the genetic material that stores information regarding its own replication
DNA also stores information regarding the order in which amino acids are to be joined
together to make a ________________
DNA is made of _____________________
Every nucleotide is a molecular complex of three types of unit molecules:
 ____________________
 Pentose sugar
 Nitrogen-containing _________________
There are four different types of nucleotides in DNA
 The base can be one of the _________________, adenine or guanine
o Each of these has a double ring
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
The base can be one of the pyrimidines, thymine or cytosine
o Each of these have a _________________ ring

The structures are called bases because their presence raises the _____ of a
solution
Nucleotides join in a definite sequence
 The nucleotides form a linear molecule called a ______________, in
which the backbone is made up of phosphate-sugar-phosphate-sugar, with
the bases projecting to one side of the backbone
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
Since the nucleotides occur in a definite order, so do the
_______________
DNA is double stranded, with the two strands twisted around each other in the form of a
double __________________
The two strands are held together by hydrogen bonds between purine and pyrimidine
bases
When unwound, DNA resembles a _____________________
 The sides of the ladder are made entirely of phosphate and sugar
molecules and the rungs are made only of complementary paired bases
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Complementary based pairs?
 thymine is always paired with _________________
 guanine is always paired with _________________
The sequence of nucleotides in DNA directs the order of ________________ acids to be
joined to make a protein.
There are only four nucleotides, but there are 20 amino acids found in proteins.
So, one nucleotide ______________ code for one amino acid
So, it takes a ___________________ of nucleotides to code for an amino acid.
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If we think of a nucleotide, or the base of the nucleotide, as the letter in a code word, we
could have combinations of two letters in each code word for more than 4 amino acids
To code for more than 16 amino acids, it takes a group of three nucleotides in a “code
word”
The “code words,” here, are called ___________________
A few interesting things about codons:
 Most amino acids have more than one ___________________
 Each triplet codon has only one meaning
 The code has start and _____________ signals
 There’s only one start signal, but there are three stop signals.
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