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Biological Molecules 2 - Topic 1.3 - Biology > Topic 3 - How DNA works > Flashcards

Topic 3 - How DNA works Flashcards

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1
Q

who discovered the double helix model

A

Watson and Crick

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2
Q

what were the 3 predicted models about how DNA replication happens

A
  • Conservative
  • Semi-conservative
  • Dispersive
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3
Q

how does conservative replication work

A

where the entire original DNA molecule stays intact and a completely new copy is made

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4
Q

how does semi-conservative replication work

A

when DNA copies itself, each new DNA molecule is made of one strand from the original DNA and one newly created strand

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5
Q

how does dispersive replication work

A

when the original DNA breaks into pieces, and the new DNA is formed by mixing pieces of the old DNA with newly synthesized DNA

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6
Q

who discovered that DNA replicates by the semi-conservative model

A

Meselson and Stahl

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7
Q

describe the experiment that explained that DNA replicates by semi-conservative model

A

used heavy nitrogen N15 to label DNA and tracked how it shifted to lighter nitrogen N14 after replication, showing that new DNA molecules always contained one old strand and one new strand, supporting the semi-conservative model.

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8
Q

what is DNA replication

A

the process of a DNA molecule copying itself exactly

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9
Q

during which phase does DNA replication take place

A

interphase

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10
Q

Describe how the DNA molecule unwinds during the interphase

A
  1. The hydrogen bonds holding the base pairs together are broken, catalysed by DNA helicase
  2. The 2 halves pf the molecule unwind and seperate, leaving the DNA bases exposed
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11
Q

Describe how the DNA template is assembled

A
  1. free nucleotides, produced earlier by the cell, enter the nucleus
  2. The nucleotides assemble on the template DNA according to the law of base pairing
  3. The nucleotides are held in place by hydrogen bonds
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12
Q

how is the sugar-phosphate backbone formed

A

by a condensation reaction linking the new nucleotides together, catalyzed by DNA polymerase

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13
Q

What are the 2 functions of the enzyme DNA polymerase

A
  • catalyses the reaction between the nucleotides
  • ‘proof reads’ the new strands
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14
Q

why are new strands of DNA produced in segments and later joined together

A

because there are more than one replication sites in each DNA molecule

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15
Q

what is the function of DNA ligase

A

catalyses the joining of new DNA segments

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16
Q

Describe how the DNA rewinds in step 4

A

each daughter DNA molecule rewinds into a double helix

Biological Molecules 2 - Topic 1.3 - Biology (7 decks)

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