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A-level biology > Nucleic acids > Flashcards

Nucleic acids Flashcards

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1
Q

what are polynucleotides

A

polymers made from nucleotides

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2
Q

give two examples of polynucleotides

A

DNA, RNA

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3
Q

give examples of nucleic acids that aren’t polymers

A
  • ATP/ADP
  • NADP+
    -NAD+/FAD
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4
Q

describe the structure of a general nucleotide

A

phosphate group-pentose sugar-nitrogenous base

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5
Q

describe the structure of a DNA nucleotide

A

phosphate group-deoxyribose-nitrogenous base

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6
Q

what are the four possible nitrogenous bases of a DNA nucleotide

A

-thymine
-adenine
-guanine
-cytosine

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7
Q

describe the structure of an RNA nucleotide

A

phosphate group-ribose-nitrogenous base

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8
Q

what are the four possible bases of a RNA nucleotide

A

-adenine
-guanine
-cytosine
-uracil

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9
Q

name the complementary base pairs in DNA

A

thymine+adenine
guanine+cytosine

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10
Q

why are DNA/RNA polymers

A

made from small, soluble, single repeating units called nucleotides. many nucleotides can be bonded together to form the much larger polymers

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11
Q

name the bonds between A-T

A

2 hydrogen bonds between the bases

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12
Q

name the bonds between G-C

A

3 hydrogen bonds between these bases

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13
Q

name the structural features of DNA (7)

A
  • polynucleotide (polymer) made from many DNA nucleotides (monomers)
  • double stranded helix
  • antiparallel strands
  • complementary base pairing between the strands/nitrogenous bases
  • via hydrogen bonding
  • A=T G—C
  • nucleotides bonded via strong phosphodiester bonds (forming a sugar-phosphate backbone)
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14
Q

what shape are the chromosomes in eukaryotic cells

A

linear

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15
Q

explain the stability of DNA

A
  • hydrogen bonding links the complimentary base pairs
  • phosphodiester bonds protect the more chemically reactive nitrogenous base pairs in the helix
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16
Q

how does the structure of DNA relate to its function (5)

A
  • it has a stable structure due to the phosphodiester (covalent) bonds and its double stranded helix shape
  • double stranded, replication can occur using one strand as a template
  • weak hydrogen bonds between complementary base pairs, easy to ‘unzip’/separate strands during replication
  • large molecule, can carry lots of information
  • complimentary base pairing allows identical copies to be made
17
Q

what is the function of DNA (3)

A
  • hereditary material can be passed on, passing genetic information from generation to generation
  • genetic code holds information for synthesising proteins
  • molecule separated, exposes sections of code for mRNA (DNA replication)
18
Q

describe the process of DNA replication

A
  • DNA helicase unwinds DNA helix
  • breaks the hydrogen bonds separating the two strands
  • both strands act as a template for forming new strands
  • free, activated DNA nucleotides complimentary base pair via hydrogen bonds
  • DNA polymerase forms phosphodiester bonds between the nucleotide monomers
  • condensation reaction occurs, using ATP, water is released
19
Q

how are DNA and RNA different based on their pentose sugar

A

DNA nucleotide contains deoxyribose sugar, RNA nucleotide contains ribose sugar

20
Q

how are DNA and RNA different based on their nitrogenous bases

A

DNA contains bases adenine, thymine, cytosine and guanine
RNA contains bases adenine, uracil, cytosine and guanine

21
Q

how are DNA and RNA different based on their length

A

DNA is very long, RNA is relatively short

22
Q

how are DNA and RNA different based on their shape

A

DNA has a linear, double stranded helix, coiled shape
mRNA has a linear, single stranded shape
rRNA has a bulky with proteins shape
tRNA has a bulky t-shaped shape

23
Q

how are DNA and RNA different based on their cell location

A

DNA is found in the nucleus
mRNA is found in the nucleus and the cytoplasm
rRNA is found in the cytoplasm attached to the RER
tRNA is found in the cytoplasm attached to amino acids

24
Q

how are DNA and RNA different based on their lifespan

A

DNA is very stable and has a long lifespan, RNA often breaks down so has a short lifespan

25
Q

how are DNA and RNA different based on their role

A

DNA is designed to store genetic information and code for building proteins
RNA is used for protein synthesis

26
Q

describe step one of meselson and Stahl’s experiment on DNA replication

A

-bacteria are grown in a broth containing the heavy N15 isotope
- dna contains nitrogen in its bases
- so as the bacteria replicated they used the nitrogen in the broth to make new DNA nucleotides
- after some time the culture of bacteria had DNA containing only the heavy N15

27
Q

describe step two of meselson and Stahl’s experiment on DNA replication

A
  • DNA from the N15 culture of bacteria was extracted and spun in a centrifuge
  • it showed dna containing the heavy n15 settled near the bottom of the centrifuge tube
28
Q

describe step three of meselson and Stahl’s experiment on DNA replication

A
  • the bacteria containing only N15 dna was taken out of the N15 broth and placed in one of a lighter N14. the bacteria was then left so that one round of DNA replication could occur. their dna was then extracted and spun in a centrifuge
  • (if conservative dna replication had occurred) - the original template dna molecules would only contain the N15 and settle at the bottom of the tube, and the new dna molecules would only contain the lighter N14 and settle at the top of the tube
  • (if semi-conservative replication had occurred) - all the dna molecules would contain the N14 and N15 and settle in the middle of the tube

the second form of replication occurred and the scientists confirmed that DNA underwent semi-conservative replication

29
Q

what were the three possible forms of dna replication did people research

A
  • semi-conservative (proven)
  • conservative (disproven)
  • dispersive replication (disproven)

A-level biology (30 decks)

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