Function of nucleic acids

?
What are the components of a nucleotide?
- phosphate
- organic nitrogeneous base
- pentose sugar (dexoyribose / ribose)
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What are the two groups of organic nitrogeneous bases?
Pyrimidine - single ring.

Purin - double ring.
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What nucleotides are under the pyrimidine (single ring) group?
- cytosine
- thymine
- uracil (replaces thymine in RNA)
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What nucleotides are under the purin (double ring) group?
- guanine
- adenine
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Nucleotide structure:
a - phosphate
b - pentose sugar
c - organic nitrogeneous base
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Which nucleotides as given previously form complementary base pairs with each other?
cytosine + guanine

adenine + thymine or uracil
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Why do cytosine and guanine form complementary base pairs with each other?

Why do adenine and thymine or uracil form complementary base pairs with each other?
They form three hydrogen bonds

They form two hydrogen bonds
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What does DNA stand for?

What pentose sugar is involved in DNA?
Deoxyribonucleic acid

Deoxyribose
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DNA:
a - nucleotide
b - 5' end
c - 3' end
d - hydrogen bonds
e - sugar phosphate backbone
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Why does DNA replicate in cell division?

What stage of cell division does DNA replication take place in?
So that each daughter cell receives an exact copy of the genetic information.

Interphase.
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DNA replication fork:
a - DNA helicase
b - free DNA nucleotide
c - DNA polymerase
d - newly synthesised strands
e - DNA polymerase
f - template strand
g and h - 5'
i and j - 3'
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How does the this stage work?
DNA unwinds.
Hydrogen bonds holding complementary base pairs break, DNA helicase catalyses it and 2 strands seperate.
Each strand is a template.
Free nucleotides opposite compl. bases.
Polymerase catalyses condensation reaction from 5' to 3'.
new DNA mol
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What is the conservative theory for DNA replication?
The original double helix molecule remains intact + fully conserved and a whole new DNA molecule is made.
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What is the dispersive theory for DNA replication?
Each new molecule of DNA contains fragments of the original double helix and newly replicated DNA.
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What is the semi - conservative theory for DNA replication?
Each strand in the original double helix acts as a template to synthesise a new polynucleotide strand.

Each new DNA molecule contains one template strand and one newly replicated strand.
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Who provided evidence for semi conservative replication?
Matthew Meselson
+
Franklin Stahl
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Which bacteria was used in this study and why?
E.Coli

easy to culture and the DNA is not contained within a nucleus.
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What was the first step in the procedure of this study?
E.Coli grown in medium containing amino acids with heavy isotope 15N.

All bacteria DNA contained this heavy isotope.

DNA extracted and suspension then centrifuged.
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What was the next step in the procedure?
Bacteria washed and then transferred to a medium containing amino acids with lighter isotope 14N.

they were allowed to divide once - one generation.

DNA extracted and then centrifuged.
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What theory did this disprove consequently?
Conservative theory
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What was the final step in the procedure?
Bacteria allowed to divide again - two generations - on the 14N medium and then the DNA was centrifuged.
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Which theory did this then disprove of?
Dispersive theory.
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Why was this experiment conclusive evidence of semi conservative and not conservative?
After one generation conservative replication wouldn't give a middle band but just at the top - light - and the bottom - heavy.
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Why was this experiment conclusive evidence of semi conservative and not dispersive?
Dispersive would only produce one band not two which would then get progressively higher in the test tube.
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Other cards in this set

Card 2

Front

What are the two groups of organic nitrogeneous bases?

Back

Pyrimidine - single ring.

Purin - double ring.

Card 3

Front

What nucleotides are under the pyrimidine (single ring) group?

Back

Preview of the front of card 3

Card 4

Front

What nucleotides are under the purin (double ring) group?

Back

Preview of the front of card 4

Card 5

Front

Nucleotide structure:

Back

Preview of the front of card 5
View more cards

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