DNA Replication and Protein
Synthesis
DNA
• Genetic material found in the nucleus
• Stands for deoxyribonucleic acid
• Lacks a oxygen, has ribose (sugar), and
nucleotides (nucleic acid)
DNA structure:
DNA is double helixed- it has 2 strands
twisted together
-When unwound it looks like a ladder
DNA composition:
• DNA is made up of
units called
nucleotides.
• Each nucleotide is
made up of a:
– 1. phosphate,
– 2. sugar, and a
– 3. nitrogen base
(there are 4 types)
4 nitrogen bases in DNA:
1.
2.
3.
4.
Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T)
A=T and C=G
**The combinations
of these bases
determine the
genetic code
(each person has
a unique code)
-Each is held
together by a
hydrogen bond
How is DNA Replicated in
Mitosis/Meiosis
DNA never leaves
nucleus
1. DNA unwinds and is
split apart
2. A copy is made of
each strand (this
occurs in the nucleus
of the cell)
Snork Worksheet
Write this on a separate sheet)
• DNA
A
C
C
G
G
T
T
A
T
A
G
C
C
G
A
G
G
G
mRNA
tRNA
A.A.
trait
How new PROTEINS are
made in the cell?
1. DNA is copied by RNA
(called Transcription)
-RNA has the same base pairs as DNA
except uracil replaces Thymine (A=U,
G=C)
Proteins from DNA contd.
1. DNA is copied to RNA in the nucleus.
2. The RNA is taken to the ribosomes. The
RNA is then used to make proteins.
2. Proteins are made from the
RNA (called Translation)
-When RNA has finished
copying DNA in nucleus
the RNA goes to the
surface of the ribosomes
(This RNA is called
messenger RNA)
-The RNA enters the
ribosome and proteins
are made from the mRNA
copy (tRNA)
How are proteins made from
DNA?
• The sequence of DNA will code for certain
proteins
• Each set of 3 bases will code for 1 amino
acid
Ex. AAA codes for the protein
lysine
• A set of 3 bases that codes is called a
codon
DNA
T
a
C
A
G
C
T
A
C
G
C
A
RNA
2. contd.
-The codon that tells translation to start is
AUG
-The codon to stop is UAA