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ZZZ AS level: Biology > DNA > Flashcards

DNA Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are genes?

A

sections of DNA which code for particular protein and amino acid

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2
Q

what type of molecule is DNA?

A

macromolecule of chain of nucleotides

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3
Q

what does a nucleotide consist of?

A
  • pentose group (ribose/deoxyribose)
  • phosphate group
  • nitrogenous-containing base
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4
Q

how do the sugar and phosphate group link?

A

by condensation reaction
- forms a sugar-phosphate backbone

  • this enables mononucleotides to be linked together
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5
Q

what is a dinucleotide?

A

two mononucleotides linked together by sugar-phosphate backbone

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6
Q

what is a polynucleotide?

A

long chain of mononucleotides

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7
Q

what are the base groups?

A
  • cytosine
  • guanine
  • adenine
  • thymine
  • uracil
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8
Q

what are the two complementary pairs?

A
  • C G

- A T

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9
Q

how many hydrogen bonds do CG have?

A

three

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10
Q

how many hydrogen bonds do AT have?

A

two

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11
Q

what is different about the base groups in RNA?

A

uracil instead of thymine

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12
Q

which base groups are pyrimidines?

A
  • cytosine
  • uracil
  • thymine

(made of one 6-sided ring and one 5-sided ring)

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13
Q

which base groups are purines?

A
  • adenine
  • guanine

( made of one 6-sided ring)

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14
Q

how does DNA form double helix?

A
  • 2 polynucleotides held together by hydrogen bonds

- strands are anti parallel so they are synthesises in opposite directions from 5’ to 3’

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15
Q

when does DNA replication occur?

A

during interphase

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16
Q

how does DNA unzip initially?

A
  • double helix unwinds

- DNA helicase unzips strand by breaking hydrogen bonds between nitrogenous bases - 3 between CG and 2 between AT

17
Q

how do free nucleotides join?

A
  • there are free nucleotides in nucleus
  • DNA polymerase reads off template strand and links nucleotides by way of complementary base pairing (purines/pyrimidines) - CG/ AT1
18
Q

how is new strand linked?

A
  • new strand is linked together

- form sugar-phosphate backbone joined by covalent bonds

19
Q

how does the strands being antiparallel affect the replication?

A
  • strands are antiparallel so replication occurs backwards in one strand and forward in the other
20
Q

why is it called semi-conservative replication?

A

two DNA molecules containing parent strand and newly synthesised strand called daughter strand so it is semi-conservative as old strand remains

21
Q

what were other models for DNA replication?

A
  • conservative model: keep old helix - form another one

- dispersive replication: replicated in fragments

22
Q

what did Watson-Crick use to prove the semi-conservative replication model?

A

radioactive isotopes N15 and N14

ZZZ AS level: Biology (21 decks)

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