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DeoxyriboNucleic Acid
DNA
Structure
• DNA is made from repeating units
called nucleotides
• Nucleotides are made from 3 types of
molecules:
– Deoxyribose sugar
– Phosphate group
– Nucleic acid base (Nitrogen Base)
Nucleic Acid Base
• Four types
–
–
–
–
A – adenine
T – thymine
C – cytosine
G – guanine
• A pairs with T
• C pairs with G
Purpose of DNA
• Every Cell must have DNA, so the cell
has information on it’s life functions
• DNA is located in the nucleus, except
prokaryotes
• When a cell divides, this information
must be copied, so an exact copy can
be given to the new cell.
Replication
ATCCAGGCAAGA
I I I
I I I
TAGGTCCGTTCT
WEAK HYDROGEN BONDS
Enzyme called DNA polymerase “unzips”
the DNA strand by breaking the weak
hydrogen bonds.
As a result, there are two identical DNA
strands
ATCCAGGCAAGA
I I I
I I I
TAGGTCCGTTCT
WEAK HYDROGEN BONDS
ATCCAGGCAAGA
I I I
I I I
TAGGTCCGTTCT
WEAK HYDROGEN BONDS
Transcription and Translation
• DNA is the molecule that codes for all
cell activities. It does this by being the
code to make proteins.
• DNA is located in the nucleus but
proteins are made out in the cytoplasm
at the ribosomes.
– Ribosomes are found on the endoplasmic
reticulum.
• Need a messenger known as RNA
mRNA
• DNA is written in RNA, this is called
transcription
• 3 major differences between DNA and RNA
– DNA is double strand and RNA is a single strand
– DNA uses A, T, C, G
RNA uses A, C, G, U
• (U stands for uracil)
– DNA uses deoxyribose sugar
RNA uses ribose sugar
mRNA cont’d
TACGTATCCATT
ATGCATAGGTAA
original DNA
compliment strand
Transcribe into mRNA in Nucleus
AUGCAUAGGUAA
codon mRNA
Translate (make meaning) of the messenger RNA in Ribosome on
Endoplasmic Reticulum
methionine – histidine – argenine – stop
Each codon codes for a particular amino acid. Amino acids build a
protein molecule to carry out cells work.
DNA Review
1. What is the name of the repeating
units that makes up DNA?
2. What are the 3 molecules that make
up these units?
3. Name and spell correctly the 4
nucleic acid bases, and show which
pairs with which?