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DNA and RNA
Chapter 3
DNA
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Deoxyribonucleic acid
Located in the nucleus
Double helix

Twisted ladder

DNA Nucleotide
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Sugar - Deoxyribose
Phosphate
Base
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Adenine – Thymine
Guanine – Cytosine
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Sides of ladder are
consisted of sugars and
phosphates
Rungs of ladder are
consisted of nitrogen
bases

Hydrogen bonds –
holds bases together
DNA Replication

One strand of DNA “unzips” and make two
strands of DNA by binding with free
nucleotides
DNA Replication
RNA
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Different types are used to translate
instructions from DNA into making proteins
Ribonucleic acid
Located in the cytoplasm

RNA Nucleotide

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Sugar - Ribose
Phosphate
Base
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Adenine – Uracil
Guanine – Cytosine
Complementary Base Pairing

DNA
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A-T
C-G
Examples of DNA
replication:
RNA
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
A-U
C-G
Examples of
transcription:

A-T-C-G-G-C-A-T-C

A-T-C-A-C-A-G-T-A

A-A-C-T-G-G-G-C-G
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C-A-G-G-A-C-T-A-G
RNA

Three types of RNA

Messenger RNA (mRNA)

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Ribosomal RNA (rRNA)


Half of a ladder
Hamburger bun shaped
tRNA
Transfer RNA (tRNA)

Attach to mRNA
mRNA
rRNA
Codons


Codon – a sequence of three nucleotide
bases that represents the “code” for one
amino acid
Amino acid – a building block for proteins
Codons

Start codon - tells cells to begin making
amino acids


AUG
Stop codon – tell cells to cease amino acid
production
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UAG
UGA
UAA
Transcription

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The first stage in
making amino acids
DNA is the blueprint for
making amino acids
Transcription occurs in
the nucleus
Transcription



DNA unzips and free
ribonucleotides bind to
the DNA strand
The finished product is
a mRNA strand
mRNA leaves the
nucleus and enters the
cytoplasm
Translation



The second stage in
producing amino acids
Translation occurs in
the cytoplasm
A ribosome (or rRNA)
attaches to a mRNA
and scans the mRNA
Translation

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
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One tRNA (or an anticodon)
will attach to a codon to
produce an amino acid
After an amino acid is
formed, the tRNA will
detach from the mRNA
Amimo acids are held
together by peptide bonds
Two or more amino acids
form a polypeptide

Progression of a protein



Amino acid – the building blocks of proteins
Polypeptide – two or more amino acids
Protein – several polypeptide chains