topic 2.6- structure of DNA and RNA Flashcards

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1
Q

what are nucleic acids?

A

polymers of nucleotides (eg DNA/RNA)

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2
Q

what do nucleotides consist of?

A
  • a pentose sugar (5 C)
  • a phosphate group (acidic, negatively charged part)
  • a base (contains nitrogen and has 1/2 rings of atoms)
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3
Q

describe the structure of DNA

A

a double helix made of two antiparallel strands of nucleotides linked by H bonding between complementary base pairs

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4
Q

how are nucleotides in DNA linked?

A

by phosphodiester bonds between the sugar base of one nucleotide and the phosphate group of the adjacent nucleotide

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5
Q

what are the two strands in DNA described as?

A

antiparallel- they run in opposite directions,
- one strand in the direction 5’ to 3’
- one strand in the direction 3’ to 5’

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6
Q

adenine always pairs with …. why?

A

thymine; adenine can only make 2 H bonds and thymine only needs 2 H bonds to be stable

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7
Q

cytosine pairs with… why?

A

guanine; both make 3 hydrogen bonds

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8
Q

purines

A

adenine and guanine (2 rings)

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9
Q

pyrimidines

A

cytosine and thymine

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10
Q

(1) are used by the cell to package the DNA into structures called (2)

A
  1. histones
  2. nucleosomes
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11
Q

what does a nucleosome consist of?

A
  • a central core of eight histone proteins (2 copies of 4 different types of histones) with DNA coiled around them.
  • an additional histone protein molecule, H1, binds DNA to the core particle
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12
Q

what do nucleosomes do?

A

they help to supercoil DNA

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13
Q

give and explain 3 differences between DNA and RNA

A
  1. DNA contains deoxyribose sugar; in RNA it is ribose
  2. in DNA, there are two polymers of nucleotides, making it double stranded; in RNA, there is only one polymer of nucleotides, making it single stranded
  3. DNA bases are adenine, cytosine, guanine and thymine; RNA bases are adenine, cytosine, guanine and uracil
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14
Q

draw a diagram of DNA and RNA

A

elsewhere

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