DNA as the Genetic Material Flashcards

1
Q

What are the components of DNA and RNA nucleotides?

A

Ribose Sugar, Phosphate and Base

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2
Q

What was the Chargaff Discovery?

A

There is significant DNA variation between species, thus DNA could be the genetic material.
(He looked at the number of bases in species DNA and found similar numbers of A-T and G-C)

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3
Q

What are Chargaff’s Rules?

A

A=T and G=C
The composition of DNA varies between species

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4
Q

What is the structure of DNA?

A

A double stranded helical molecule with particular features

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5
Q

What discoveries did Photo 51 (showing x-ray diffraction pattern of DNA from top view) lead to?

A
  • DNA is a helical structure
  • Bases perpendicular to the length of the DNA molecule
  • Double stranded
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6
Q

Photo 51 also showed that the diameter of DNA is constant. What discovery did this lead to?

A

The confirmation that A=T and G=C (because a purine + a pyrimidine will equal a constant diameter and these pairs also reflect the numbers found by Chargaff)

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7
Q

How do we count carbons?

A

Start at oxygen and count clockwise from there.

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8
Q

What does 3 prime and 5 prime mean in terms of nucleotides?

A

3 prime is the third carbon and it has an OH group attached to it.
5 prime is the fifth carbon and it has the phosphate group attached to it.

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9
Q

How are polynucleotides formed?

A

Nucleotide monomers join together with phosphodiester bonds to form a polynucleotide = nucleic acid (deoxyribonucleic acid for DNA)

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10
Q

What is the formation of the phosphodiester bond?

A

The hydroxyl group on the 3rd carbon of one nucleotide reacts with the phosphate group attached to the 5th carbon on another molecule.

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11
Q

What direction are DNA (and RNA) strands synthesised in?

A

The 5 prime —-> 3 prime direction

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12
Q

What does the two strands of DNA being antiparallel mean?

A

They are synthesised in the 5 to 3 prime direction but for two strands to join together and make a double helix one has to flip. This is referred to as antiparallel orientation.

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13
Q

What are the key points of DNA structure?

A

Sugar-phosphate backbone, nucleotides are pointing in towards the helix (bases are in the middle), dotted lines are hydrogen bonds.
A bonds with T (two H bonds btw them), G bonds with C (3 H bonds between them), the hydrogen bonds stabilise the molecule. Two polynucleotide strands are oriented in opposite directions.

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14
Q

What type of replication does DNA do?

A

Semi-conservative replication.
This means that each strand of DNA from the double helix is used as a template strand for the synthesis of two new strands

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