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DNA: genes on chromosomes
DNA is composed of nucleotides
A Nucleotide has:
- Deoxyribose Sugar
- Phosphate
- Nitrogen Base
Adenine
Thymine
Guanine
Cytosine
A - T and G - C
DNA is a helix molecule
Hydrogen
bonds are
in between
the bases.
Note the
nucleotides
pairing.
DNA self replicates before cell division
5’ 3’
The DNA strand opens and
will add nucleotides. A to T
and G to C.
C
A
G
T
One strand grows
continuously, the other
grows discontinuously.
Enzymes join the strands.
3’
5’
DNA produces proteins in two steps
Transcription:
mRNA
production
Translation:
protein
production
Transcription is when
the mRNA produced.
mRNA from DNA
as expected……..
GGG CCC TTT AAA
CCC GGG AAA UUU
The bases of the DNA are matched up with
the RNA bases A-U, T-A, G-C, C-G
AAA TTT GGG CCC GGG CCC TAA
UUU AAACCC GGG CCC GGG AUU
Synthesis starts at the beginning of a gene
Transcription moves in a 5’ to 3’ direction
Transcription finishes as mRNA is released
The DNA triplets help code for amino acids
during translation because DNA is in control
of the triplets of mRNA (the codon). The anticodon of the tRNA matches this codon on the
ribosome and brings with it an amino acid.
UUU AAACCC GGG CCC GGG AUU
AAA UUU GGG CCC GGG CCC UAA
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Phe Lys Pro Gly Pro Gly Ile
Bonds form between amino acids
When the
chain is
complete,
a new
protein
has been
formed.
Video of
Protein
Synthesis.
On the ribosome mRNA codons match
tRNA anticodons linking amino acids
Steps to Protein Synthesis
• Transcription: Production of mRNA by
DNA in nucleus. Base pairs match up A to
U and G to C (RNA has no Thymine).
• Translation: In the cytoplasm, on the
ribosome, the mRNA codon matches tRNA
anticodon to bring the proper amino acid in
for bonding. Once the whole mRNA is read
by the ribosome, the stop codon ends the
production of the peptide chain; the protein
is complete!
How is RNA different than DNA?
•Ribose Sugar
•Uracil for
Thymine
•Single strand
•not self
replicating
•found all
over the cell
• Nucleolus - Site of ribosome production
• Nucleus - location of DNA, cell organizer
• Chromosomes - coiled chromatin
• Chromatin - DNA and proteins not coiled
• DNA - helix shaped molecule with base
sequences that make up the genetic code
• RNA - made by DNA, assists DNA to
make proteins as a messenger (mRNA),
transfer molecule (tRNA) and ribosomal
RNA (rRNA).
END!