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DNA! • DNA (deoxyribonucleic acid); which stores and
provides the information that our body needs to make the various proteins that make us who we are.
• DNA is normally in the form of a double-helix.
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DNA Model
The red arrows are pointing to nitrogen bases.
The blue arrow is pointing to a hydrogen bond; the specific bond that holds the base pairs together.
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The black arrow pointing to a deoxyribose sugar.
The green arrow is pointing to a phosphate.
The sugar and phosphate are two components of a nucleotide. A nucleotide also has a nitrogen base attached to the sugar phosphate backbone.
DNA Model
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The adenine pairs with thymine and the cytosine pairs with guanine.
The purines are adenine and guanine.
The pyrimidines are thymine and cytosine.
Base Pairing Rules
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The DNA is “unzipping” creating a replication fork. The enzyme DNA helicase binds to DNA and breaks the hydrogen bonds between the bases in the DNA strand.
Replication fork
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Replication
Completing Replication• The enzyme DNA Polymerase will
add free nucleotide bases to the exposed template according to base airing rules forming the complimentary strands.
• Each new DNA molecule will have 1 side of original DNA and one side of “new” DNA
• The enzyme DNA Polymerase will continue to work “proofreading” both new strands for errors
• The enzymes DNA Polymerase and DNA Ligase work to complete the process re-twisting the two new strands
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Complete the following…
This strand is called .
The backbone is composed with a sugar instead of a deoxyribose sugar.
There is a base substitution of instead of .
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This strand is mRNA.
Its backbone is composed with a ribose sugar instead of a deoxyribose sugar.
It uses a base of uracil instead of thymine .
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Protein Synthesis – Step #1
What step of protein synthesis is being shown in the picture?
Why do cells need mRNA?
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The picture is showing transcription - mRNA is matching base pairs (substituting U for T) in order to get the information from the DNA out into the cell’s cytoplasm.
Cells need mRNA for two main reasons:
1) DNA strands are too LARGE to leave the nucleus
2) DNA needs to stay in a central location so that it can continuously provide information for differing genes and their protein requirements
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mRNA goes to the ribosome in the cytoplasm.
The mRNA lines up on the ribosome in groups of three bases, called codons.
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What is this structure?
Where is this structurefound in a cell?
What are these three nucleic acid bases called? 19
This structure is tRNA.
Reminder: Since it is a type of RNA, uracil is used instead of thymine.
tRNA is found only in the cytoplasm of a cell.
These bases are an anti-codon. This will pair with a corresponding codon from mRNA according to base pairing rules.
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Translation: the codon on mRNA matches up with the anticodon on tRNA. Each tRNA carries a specific amino acid with it when it arrives at the ribosome. The ribosome (made of rRNA) plays a role by helping codon match with anticodon.
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tRNA molecules continually bring specific amino acids to the ribosome according to what the mRNA requests.
The amino acids connect with one another using specific bonds called:
Complete the following…
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tRNA molecules continually bring specific amino acids to the ribosome according to what the mRNA requests.
The amino acids connect with one another using specific bonds called: peptide bonds
Complete the following…
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Describe what happens once all of the information originally from the DNA is translated and all of the amino acids are joined together into polypeptide
chains.
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