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biology a level OCR > Nucleotides and Nucleic acids > Flashcards

Nucleotides and Nucleic acids Flashcards

1
Q

what are nucleotides

A
  • monomers of nucleic acids (RNA and DNA)
  • carbon, hydrogen, oxygen, nitrogen and phosphorus
  • component of coenzyme NAD and FAD
  • ATP, ADP AMP all contain adenine base
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2
Q

what are the components of a nucleotides

A
  • pentose (5 carbon) sugar - deoxyribose (DNA), ribose (MA + ATP)
  • a phosphate group
  • nitrogenous base
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3
Q

what are the three parts of a nucleotide

A
  • pentose sugar
  • nitrogenous base
  • negatively charged phosphate group
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4
Q

what are the four different bases in DNA nucleotides

A
  • Adenine
  • thymine
  • guanine
  • cytosine
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5
Q

what are purines

A

double ring carbon structure

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6
Q

what are pyrimidines

A

single ring carbon ring

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7
Q

what is the base for RNA

A

Uracil

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8
Q

what is the bond between two adjacent nucleotides called

A

a phosphodiester bond

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9
Q

what are the stages, Chargaff’s ratios of bases in DNA

A

stage 1 - extract DNA - needs detergent, salt, proteases and ethanol
stage 2 - add protease enzyme - digests the histone proteins.
stage 3 - heat, with a strong acid, to hydrolyse DNA, plus release nucleotide base.
stage 4 - separated bases, using paper chromatography
stage 5 - used a spectrophotometer, allows, determination, of the amount of each base - bands extracted, into solution, results read using UV light

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10
Q

what does antiparallel mean

A
  • 2 strands, run in opposite directions
  • each strand, has a phosphate group, attached to carbon 5’ at one end and a hydroxyl group, attached to 3’ at the other end.
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11
Q

what does adenine pair with

A

thymine ( 2x hydrogen bonds)

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12
Q

what does Guanine pair with

A

cytosine ( 3x hydrogen bonds)

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13
Q

what type of bond join nucleotides together in polynucleotides

A

phosphodiester bond

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14
Q

what is DNA replication

A
  • occurs in the nucleus, during interphase, of the cell cycle - specifically the synthesis or S phase
  • 1 chromosome into 2 sister chromatids
  • occurs in mitochondria + chloroplasts just before the cell divides
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15
Q

what materials are required for DNA replication

A
  • DNA polymerase enzyme, helicase enzyme, gyrase enzyme and ligase enzyme.
  • free DNA nucleotides (a, c, g, t)
  • intact DNA -> this is because both strands, act as a template for replication
  • energy source (ATP), to phosphorylase nucleotides, which activates them.
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16
Q

why is DNA semi - conservative

A

in each new DNA molecule, one old strand is conserved and paired with 1 new strand.

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17
Q

how many base pairs are there in the human genome?

A

10x10(to the power of 9)

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18
Q

the semi - conservative model of DNA replication

A
  • DNA molecule, unwinds (gyrase) and unzips (helicase) -> unzips the double helix, by breaking the hydrogen bond between the two strands
    free nucleotides in the nucleus, + 2 extra phosphate groups are added to nucleotides, to active them (involves ATP)
  • bases of the activated nucleotides pair up, with complementary bases. on each of the old strands.
  • DNA polymerase, catalyses the formation of phosphodiester bonds, joining the nucleotides together, 5’ to 3’ direction
  • on the lagging strand, or Okazaki fragments form, which leaves gaps in the new strand, these gaps are later filled in using ligase enzymes.
  • 2 additional phosphate groups are broken off the activated nucleotides and Okazaki fragments are released.
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19
Q

what are the 3 things that a mutation can be?

A
  • neutral
  • harmful
  • beneficial
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20
Q

what is the semi - conservative model for DNA replication

A
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21
Q

summarise Meselson and Stahl experiment on DNA replication

A
  • scientist, grew many generations, e.g. in heavy N15 all bacterial DNA was heavy
  • took a sample -> span in centrifuge -> heavy band N0
  • then placed N0 in to N14, medium after 20 mins, took N1 sample -> hybrid intermediate band
  • then allowed N1 to divide -> N2 -> results intermediate band + light
  • over more generations, light band becomes thicker
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22
Q

what is the function of DNA ligase

A

DNA ligase catalyses condensation reactions between the new nucleotides to create a polynucleotide chain.

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23
Q

what is the function, of the enzyme gyrase

A

catalyses the ATP-dependent negative super-coiling of double-stranded closed-circular DNA

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24
Q

what is the function of the enzyme helicase

A

unwinds the DNA by breaking the hydrogen bonds between complementary base pairs on the two strands of DNA.

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25
Q

what is the function of DNA polymerase

A

to accurately and efficiently replicate the genome in order to ensure the maintenance of the genetic information and its faithful transmission through generations.

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26
Q

name 2 purines

A

adenine and guanine (double ring)

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27
Q

name 2 pyrimidines

A

thymine and cytosine (single ring)

28
Q

a purine always pairs with a pyrimidine

29
Q

why do we say that the two strands in DNA are antiparallel

A

because they run in opposite directions

30
Q

what does carbon 5 attach to

A

the phosphate

31
Q

what does carbon 3 attach to

A

the hydroxyl group

32
Q

why is the proportion of Adenine - thymine and cytosine - guanine the same

A

due to complementary paring

33
Q

what structure, do the two polynucleotide strands, form when they twist around each other

A

a double helix

34
Q

what sugar is found in DNA

A

deoxyribose

35
Q

what sugar is found in RNA

36
Q

state some facts about DNA

A
  • in chromosomes in the nucleus
  • extremely long molecule
  • two polynucleotide strands in a double helix
37
Q

state some facts about RNA

A
  • in the cytoplasm
  • relatively short molecule
  • one polynucleotide strand
38
Q

what happens when a cell undergoes cell division

A

all of its DNA is copied

39
Q

what is DNA replication

40
Q

what is the difference between a normal nucleotide and an activated nucleotide

A
  • an activated nucleotide contains 3 phosphate groups
  • a nucleotide only contains one phosphate group
41
Q

what happens in semi - conservative DNA replication

A
  • the DNA helix, separates into two polynucleotide strands.
  • each strand is then replicated into a complementary new strand
  • one molecule of DNA, is thus copied into 2 molecules of DNA
  • each of the two copies of DNA, contains one strand from the original DNA molecule and one new strand.
42
Q

what is conservative replication

A
  • a DNA double helix is formed containing two new strands of DNA
  • one strand, comprises of old DNA
  • one strand, comprises of completely new DNA
43
Q

what do all bases in DNA contain

44
Q

what are the two main forms of nitrogen

A
  • N14 ( light nitrogen )
  • N15 ( heavy nitrogen )
45
Q

what does the position of the DNA band in the test tube depend on

A

it depends on how heavy the DNA is

46
Q

what is the structure of RNA

A

single stranded, ribose sugar, with uracil instead of thymine

47
Q

what is the function of RNA

A

involved in protein synthesis

48
Q

what is messenger RNA

A
  • single stranded molecule, forms a helical shape
  • product, of transcription in the nucleus.
  • copy of the DNA coding strand (sense) or complementary to the DNA template strand (antisense) (except U replaces T)
  • moves out of the nucleus, via nuclear pore. (using microtubules, for movement attaches to a ribosome)
49
Q

what is transfer RNA

A
  • smaller molecule, than mRNA (80nts comparted to ~1000nts)
  • made in the nucleus + transported, into the cytoplasm
  • clover leaf shape
  • can attach, to a specific amino acid
  • 3 exposed bases -> anti codon, determining which amino acid is attached, + binds to the codon of mRNA, to ensure that a sequence of amino acids forms in the correct order.
50
Q

what is ribosomal RNA

A
  • produced in the nucleolus
  • produced, from DNA
    combined with ribosomal proteins
  • 2 sub units ( one larger subunit and one smaller subunit)
  • eukaryote -> 80S size (ribosomes)
  • archaea + bacteria -> 70S size (smaller)(ribosomes)
51
Q

give two places, where you find find ribosome in the cell

A
  • cytoplasm
  • RER
52
Q

what does the nucleolus do

A

produce ribosomal RNA + assembles ribosomes

53
Q

what makes species different from each other

A

the sequence of amino acids

54
Q

what is the amino acid base code called

A

the triplet code.

55
Q

what happens, if a base is added or deleted

A

it causes a frame shift, as every triplet after that is changed and this could affect every amino acid

56
Q

why does protein synthesis occur

A

because DNA, is to large to leave the nucleus - mRNA, is small enough, to move out of the nucleus, via a nuclear pore.

57
Q

describe the steps of transcription

A
  • in the nucleus the gene unwinds (gyrase) and unzips (helicase) exposing the bases on DNA
  • free activated nucleotides (RNA), line up, complementary to the DNA template strand
  • RNA polymerase, binds to the promoter region of the gene and joins the RNA nucleotides together, with a phosphodiester bond , forming a sugar phosphate backbone -> primary RNA
  • when the RNA polymerase, reaches the stop triplets, it detaches, primary RNA is spliced, to remove introns (non - coding regions)
  • exons are joined together by (ligase)
  • mature RNA, leaves nucleus + enters cytoplasm.
58
Q

what is RNA polymerase

A

the enzyme that synthesis mRNA from DNA in transcription

59
Q

what are the 4 requirements, for translation

A
  • mRNA + ribosome
  • tRNA (transfer RNA)
  • enzymes
  • proteins from the cytoplasm
60
Q

what is the initiation codon

A

the first codon to be translated from the mRNA, is always AUG.

61
Q

what is meant, when the triplet code, is said to be non - overlapping

A

it means, that no base is read more than once

62
Q

what are the 3 triplets, that determine where translation stops

A
  • UAA
  • UAG
  • UGA
63
Q

what is each triplet in mRNA called

64
Q

describe the process of translation

A

https://youtu.be/nekOPRY94aI?t=310

65
Q

what happens, when a ribosome gets to a stop codon, during translation

A

it detaches and the polypeptide chain is released

66
Q

where does transcription take place

A

in the nucleus

biology a level OCR (32 decks)

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