1. Describe the basic structure (double helix,
sugar/phosphate backbone, linked by complementary
nucleotide pairs) of DNA, and describe its function in
genetic inheritance.
2. Describe the basic process of DNA replication and
how it relates to the transmission and conservation of
the genetic code.
3. Explain the basic processes of transcription and
translation, and how they result in the expression of
genes.
4. Distinguish among the end products of replication,
transcription, and translation.
Explain the Central Dogma of Biology.

 DNA is in the group of organic molecules called nucleic acids.
 Nucleic Acids are macromolecules made up of subunits called nucleotides
 Genes are coded messages of how, when, and where to make proteins, and are
sections of a long DNA molecule.
 In Eukaryotic cells DNA is found in nucleus either in chromatin or in chromosomes
- Chromatin – Unraveled DNA in the nucleus
- Chromosome – DNA wrapped around protein spools in the nucleus

 DNA is made up of subunits called nucleotides.
 There are 4 different types of nucleotides of DNA:
Nucleotides with Adenine, (A)
Nucleotides with Guanine, (G)
Nucleotides with Thymine, (T)
Nucleotides with Cytosine, (C)
 Each nucleotide is made up of three parts
A phosphate group
A deoxyribose sugar
A nitrogen base, there are 4 bases, (A,T,C,G)
 DNA consists of two strands of nucleotides
with sugars and phosphates on the outside
and bases bonded together on the inside.
 The paired strands twisted zipper shape is
called a double helix.
The form of DNA is a double helix

 The base adenine (A)
bonds with thymine (T)
 The base guanine (G)
bonds with cytosine (C).
 These bases are bonded
together by hydrogen
bonds.
 This is known as
complementary base
pairing!
Explain complimentary base pairing.

 DNA has two functions:
◦ 1. Hold information on how to make proteins
◦ 2. Make more DNA
 The main function of DNA is to store genetic information.
 The information that DNA stores is how, when, and where to make
proteins.
• Genes are sections of DNA that have the
information for how to build one protein.
• DNA is the molecule of heredity.
 The second function of DNA is simply to make more DNA; this is
called replication.

 DNA replication is the process of DNA making more DNA.
◦ Replication begins when an enzyme binds to the DNA.
◦ The enzyme (Helicase) separates the joined base pairs (or unzips
the double helix).
◦ As the nucleotides separate another enzyme (DNA polymerase)
binds to the separated chains and begins to assemble free
nucleotides into new double helixes.
View this DNA Synthesis Animation
Here’s an animation on bacterial
DNA replication

Transcription - DNA is
transcribed into RNA
In mRNA, a three nucleotide
sequence is known as a codon. Each
codon identifies a particular amino acid.
The amino acid order is determined
by the order of codons.
The amino acid order also determined
the protein’s shape (form).
A protein’s shape allows it to carry out
a specific function

 There are three types of RNA
◦ Messenger RNA (mRNA) - is a strand of nucleic acid with the DNA's
information on the order of amino acids for a certain protein encoded
on it.
◦ Transfer RNA (tRNA) – “Translator” – in the translation process,
converts nucleic acid codes to amino acid.
◦ Ribosomal RNA (rRNA) – “Protein Factory” – translation occurs
here. Contain binding sites for tRNA and mRNA.
mRNA
rRNA
tRNA

 In the nucleus a second type of
nucleic acid is made based on the
order of nucleotides making up the
codons and genes: RNA
 Messenger RNA (mRNA) is a type of
nucleic acid
 The process of copying DNA’s
information into mRNA is called
transcription.
 The job of mRNA is to deliver the
DNA’s information to the cytoplasm
where proteins are made.

 mRNA is made up of subunits called nucleotides.
 There are 4 different types of nucleotides of RNA:
◦ Nucleotides with Adenine, (A)
◦ Nucleotides with Guanine, (G)
◦ Nucleotides with Uracil, (U)
◦ Nucleotides with Cytosine, (C)
 Each nucleotide is made up of three parts
◦ A phosphate group
◦ A ribose sugar
◦ A nitrogen base, there are 4 bases, (A,U,C,G)
 In mRNA, a three nucleotide sequence
is known as a codon. Each codon
identifies a particular amino acid.
 The amino acid order is determined by
the order of codons.
 The amino acid order also determined
the protein’s shape (form).
 A protein’s shape allows it to carry out
a specific function

 Transcription is the process of making RNA from a DNA template.
 Transcription of RNA occurs in the nucleus
 There are three stages to Transcription:
◦ Initiation – an enzyme (RNA Polymerase) attaches to DNA at the
promoter region.
 The promoter region contains a start codon, methionine (AUG).
◦ Transcription – RNA synthesis begins. A (on DNA strand) will bond to U
(on RNA strand). There are no T’s on RNA strands.
◦ Termination – RNA Polymerase reaches locations containing stop
codons, (UAA, UAG, UGA), at this point, RNA synthesis stops. RNA
polymerase and the newly synthesized mRNA detaches from the DNA.
 The mRNA leaves the nucleus and enters the cytoplasm
View this Animation on
Transcription of RNA

 Animation of
mRNA

Transcription - DNA is
transcribed into RNA
In mRNA, a three nucleotide
sequence is known as a codon. Each
codon identifies a particular amino acid.
The amino acid order is determined
by the order of codons.
The amino acid order also determined
the protein’s shape (form).
A protein’s shape allows it to carry out
a specific function

 The process of using the DNA’s information, now on the mRNA
to produce a protein is called translation.
 Translation is a process in which the order of bases in mRNA
codes for the order of amino acids in a protein.
 Once the mRNA has moved out of the nucleus into the
cytoplasm, the process of making a protein begins.
◦ Cytoplasm is filled with nutrients like amino acids
View this animation on Translation

 The ribosome attaches to
mRNA to begin making
proteins.
 The ribosome require amino
acids to produce proteins.
 The amino acids are brought
to the ribosome by transfer
RNA (tRNA).
 tRNA on one end contain sets
of three nucleotide (anticodon)
that forms base pair with the
mRNA codon.
 On the other end, is carried
the amino acid that
corresponds to the anticodon.
 The amino acids are
assembled one after another
based on the order of nitrogen
bases in the codons.
 Translation stops when the
ribosome encounters one of
the stop codons
(UAA, UAG, or UGA.)

•3 entities : DNA
RNA
Protein
• 3 Processes: Replication
Transcription
Translation
 DNA is replicated into more DNA
During S phase of a cell's life, DNA is replicated for new cells
DNA makes more DNA
 DNA is transcribed into RNA
The information on the DNA is transcribed into RNA
 RNA is translated into Proteins
RNA delivers the DNA’s information to the site of protein
synthesis and the DNA’s info on the RNA is translated into
protein from nucleic acid
 The central dogma of biology consists
of 3 entities and 3 processes.

 What are DNA, mRNA,and tRNA?
 What is the twisted shape of DNA called?
 What is the Central Dogma of Biology?
 Define entities, processes, and properties .
 What are the entities in the Central Dogma?
 What are processes in the Central Dogma?
 What are genes and codons?
 What are the four bases found on DNA nucleotides?
 What are the four bases found on RNA nucleotides?
 Which nucleotides are purines and which are pyrimidines?
 What enzymes are required for DNA replication?
 Which nucleotides are complimentary?
 Why can genetic information remain reasonably constant?
 What happens when mutations are made?
 What is the function of tRNA?