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Green > 2.1.3: Nucleotides and Nucleic acids > Flashcards

2.1.3: Nucleotides and Nucleic acids Flashcards

1
Q

What types of molecules are DNA and RNA and what are they both examples of ?

A

Nucleic acids and ribose sugars

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2
Q

What are nucleotides ?

A

Monomers or nucleic acids

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3
Q

What are the 4 bases in DNA ?

A

Adenine
Cytosine
Guanine
Thymine

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4
Q

What are the 2 purines and describe features of purines ?

A
  • A and G
  • Double ring structure of carbons
  • Large
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5
Q

What are the 2 pyrimidines and describe features of pyrimidines ?

A
  • C and T
  • Similar small sizes
  • 1 carbon ring
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6
Q

How many hydrogen bonds are between A and T ?

A

2

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7
Q

How many hydrogen bonds are between C and T ?

A

3

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8
Q

What are ADP and ATP examples of ?

A

Phosphorylated nucleotides

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9
Q

How is ATP formed ?

A

ADP + Pi ( inorganic phosphate )

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10
Q

What type of reaction is the formation of ATP

A

Condensation ( water released )

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11
Q

What does the structure of ATP consist of ?

A
  • Ribose pentose sugar
  • Adenine nitrogenous base
  • Inorganic phosphates
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12
Q

What enzyme is needed for the formation of ATP ?

A

ATP synthase

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13
Q

Describe the structure of a DNA nucleutide

A
  • Phosphate group (makes nucleotide negatively charged)
  • Hydrogen bonds between complementary based pairs
  • Nitrogenous bases
  • Deoxyribose pentose sugar
  • Phosphodiester bonds connecting nucleotides
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14
Q

What type of bond is a phosphodiester bond and how is it formed/ broken ?

A
  • Covalent bonds
  • Condensation reaction / hydrolysis
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15
Q

Give the function and features of ATP ?

A
  • Metabolism
  • Enables energy from glucose to be released in small , useful and non armful amounts that wont waste heat energy in cells if released too quickly
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16
Q

What is the formula of DNA ?

A

C5H10O4

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17
Q

What is the formula of RNA ?

A

C5H10O5

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18
Q

Give 4 comparison features between DNA and RNA

A

DNA is ..
- Longer
- Double stranded
- Thymine instead of Uracil
- 1 less oxygen

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19
Q

What does non-coding DNA do ?

A

Codes for regulatory genes

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20
Q

What is the function of DNA ?

A

Codes for sequence of amino acids in primary protein structure

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21
Q

Outline the features of a DNA molecule

A
  • Double helix shape produced by twisting
  • Anti parallel strands as rungs are same distance apart down DNA length
  • Stable structure due to sugar-phosphate backbone joined by phosphodiester bonds
  • Weak hydrogen bonds for easy separation during replication
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22
Q

Outline the key steps of DNA precipitation

A

1) Homogenise cells with detergent and salt
2) Filter
3) Add protease
4) Place in 60 degrees water bath for 15 minutes
5) Stand beaker in iced water
6) Add ice cold ethanol down side of tilted glass
7) Use glass rod to remove precipitated DNA which appears as white strands

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23
Q

Why does homogenisation ( salt and detergent) occur during DNA precipitation ?

A

To dissolve the phospholipid bilayer/nuclear envelope and to break the hydrogen bonds between DNA and surrounding water .. help DNA shed water so it can precipitate

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24
Q

Why do we filter the solution during DNA precipitation ?

A

To remove large debris

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25
Q

Why do we add protease during DNA precipitation ?

A

To break down histone proteins associated with DNA

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26
Q

Why do we place the solution in a water bath during DNA precipitation ?

A

To denature enzymes that might break down DNA

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27
Q

Why do we stand the solution in iced water during DNA precipitation ?

A

To cool the mixture and prevent DNA degregation

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28
Q

Why do we add iced cold ethanol down the side of a tilted glass during DNA precipitation ?

A

So the filtrate meets the ethanol at interphase and precipitates

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29
Q

What does 1 gene code for ?

A

1 polypeptide

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30
Q

When in the cell cycle does Semi conservative DNA replication occur ?

A

In s phase of interphase before mitosis/ meiosis

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31
Q

What is the product of semi conservative DNA replication ?

A

1 new strand and 1 conserved strand

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32
Q

Where in a cell does semi conservative DNA replication occur ?

A

In the nucleus

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33
Q

How many strands act as a template during semi conservative DNA replication ?

A

2

34
Q

Which direction does the new strand produced from semi conservative DNA replication run ?

A

5’ to 3’ as its anti parallel to conserved strand

35
Q

Outline the steps of semi conservative DNA replication

A

1) Enzyme DNA helicase breaks hydrogen bonds between complementary bases of the 2 DNA strands
2) DNA helix unzips and unwinds at random places
3) Free activated nucleotides floating in nucleus align and complementary base pair with exposed bases on template strand
4) Hydrogen bonds form between base pairs
5) DNA polymerase is complementary to 3’ end moves 3’ to 5’ on template strand to build phosphate-sugar backbone with phosphodiester bonds

36
Q

Give the 3 features of the genetic code

A
  • Degenerate
  • Non-overlapping
  • Universal
37
Q

What does a degenerate genetic code mean ?

A

Amino acids are coded for by more than 1 triplet of bases

38
Q

What does a universal genetic code mean ?

A

The same triplet of bases code for the same amino acids in all organisms

39
Q

What does a non-overlapping genetic code mean ?

A

Each base in a gene is only part of one triplet of bases that codes for 1 amino acid

40
Q

What are the advantages of a degenerate genetic code ?

A
  • Even if a gene mutation occurs ,changing a base, it can still code for the same amino acid ( same sequence in a polypeptide chain so primary protein structure not affected, shape and function of organism not altered)
41
Q

What is the area where DNA unzips called ?

A

Replication fork

42
Q

What is the advantage of a non-overlapping genetic code ?

A

Mutations only affect 1 codon in a sequence

43
Q

What is the advantage of a universal genetic code ?

A

Can remove human insulin and insert into the plasmid of a bacterium to make human insulin

44
Q

What processes are occurring when a gene has been switched on ?

A

Transcription and translation

45
Q

Where in a cell does transcription and translation occur ?

A

In the nucleus

46
Q

Summarise in a sentence what happens in DNA transcription

A

DNA sequence for 1 gene is copied into mRNA

47
Q

Outline the steps of DNA transcription

A

1) DNA helicase breaks hydrogen bonds between complementary bases between 2 strands
2) DNA helix unwinds and unzips at random places
3) Free mRNA nucleotides align opposite exposed complementary DNA bases
G-C
A-U
4) Enzyme RNA polymerase runs 3’ to 5’ end joins RNA nucleotides by forming phosphodiester bonds and building the sugar-phosphate backbone
5) New mRNA polymer chain created
6) Transcription stops, mRNA detaches from template and is modified to become mature mRNA
7) Mature mRNA leaves nucleus through nuclear pore as mature mRNA
8) DNA double helix reforms

48
Q

What is a start codon ?

A

Enables ribosome to attach and is 3 bases long

49
Q

What is a stop codon ?

A

Causes ribosome to detach and is 3 bases long

50
Q

What are the differences between DNA and mRNA ?

A

mRNA is shorter and single stranded

51
Q

What is mRNA ?

A

Copy of 1 gene from DNA

52
Q

What is rRNA ?

A

For protein synthesis and making ribosomes

53
Q

What is a codon ?

A

3 bases on mRNA that codes for 1 amino acid

54
Q

What is an anti codon ?

A

3 bases on tRNA

55
Q

Describe the structure and function of tRNA

A

Single stranded and folded into a cloverleaf to bring specific amino acids to the ribosome

56
Q

How many strands act as a template during DNA translation ?

A

1 ( antisense strand )

57
Q

What is another name for the coding strand on a DNA molecule during DNA transcription ?

A

Sense strand

58
Q

What is a ribosome made of ?

A

Protein and rRNA

59
Q

Outline the steps of DNA translation

A

1) Modified mRNA binds to specific site on ribosome at the start codon and is held in place
2) tRNA molecule ,with complementary anti codon to start codon, aligns opposite mRNA strand by complementary based pairings
G-C
A-U
3) 2 amino acids bound to the tRNA are joined by a peptide bond ( reaction catalyzed by enzyme and ATP)
4) Polypeptide chain within the primary structure of a protein is built as it is coded for by the mRNA
5) Ribosome moves along the mRNA until it reaches the stop codon at the end where is detaches and translation stops

60
Q

How many tRNA molecules can a ribosome hold ?

A

2

61
Q

What happens to the polypeptide formed during translation after it is synthesised ?

A

It moves to the golgi via the cytoskeleton

62
Q

Why do white blood cells not need to be crushed before adding detergent in DNA precipitation ?

A

They have no cell walls to break open

63
Q

What happens if the solution is not heated during DNA precipitation ?

A

If temperature is too low, enzyme activity is reduced so DNA won’t break down

64
Q

What does the detergent act as in DNA precipitation ?

A

An emulsifier as it attracts water and phospholipid molecules

65
Q

Describe how the 2 chains in a DNA molecule are held together

A
  • Hydrogen bonds between complementary bases on chains
  • Purine to pyrimidine bonding
  • 2 hydrogen bonds between A and T, 3 hydrogen bonds between C and G
  • Nucleotides joined by phosphodiester bonds forming the backbone
66
Q

Explain how nucleotides in a DNA molecule are arranged as 2 polynucleotide strands

A
  • Nucleotides joined by phosphodiester bonds
  • Hydrogen bonds between complementary bases
  • Polynucleotides are anti parallel
67
Q

Explain how pairing of nitrogenous bases allows identical copies of DNA to be made

A
  • A pairs with T and C pairs with G due to hydrogen bonding
  • Purines can only bind to pyrimidines as they are different sizes
  • If a base is known is can pair with only one other base
68
Q

Name the type of reaction where an inorganic phosphate is used to make ATP

A

Condensation / phosphorylation

69
Q

Why at the end of the day will a small proportion of a person’s mass be ATP ?

A
  • ATP is hydrolysed
  • ATP is constantly recycled
  • ATP is not stored long term
  • ATP is used to provide energy for metabollic reactions such as protein synthesis
70
Q

Give 3 similarities between DNA replication and transcription

A
  • DNA molecule unwinds and unzips
  • Free nucleotides complementary base pair
  • Polymerase enzymes used to form phosphodiester bonds for backbone
71
Q

Give 3 differences between DNA replication and transcription

A
  • DNA vs RNA polymerase used
  • Product in DNA replication is 2 new daughter strands of DNA whereas in transcription product is one mRNA strand
  • In replication both strands act as a template whereas in transcription only one strand acts as a template
72
Q

Explain the phrase semi-conservative replication

A

New DNA molecule contains one original strand and one new strand

73
Q

What is the function of DNA helicase ?

A

Unzips the molecule by breaking the hydrogen bonds between complementary base pairs to separate the 2 strands

74
Q

What is the function of DNA polymerase ?

A

Joins the nucleotides vertically and forms phosphodiester bonds (between adjacent nucleotides) to form the sugar- phosphate backbone

75
Q

Describe how results in generations 0,1,2,10 support semi-conservative replication in Messelson and Stahl experiment

A
  • 0 generation contains a single band of DNA containing N15
  • 1st generation shows new DNA contains N14 and N15
  • Generation 2 shows new DNA is made from only N14 so N14 strand of DNA must be a template for the new molecule
  • Generation 10 shows the highest bond getting thicker as more DNA is made from only N14
76
Q

What is the last step of DNA transcription and replication ?

A

DNA molecule rewinds into a double helix

77
Q

Explain why transcription is necessary for protein synthesis

A
  • DNA is too large to leave nucleus so has to be transcribed into mRNA so it can go to translation at the ribosomes on the RER for protein synthesis
78
Q

Explain how the genetic code in a gene codes for a protein

A
  • 3 bases code for 1 specific amino acid
  • Sequence of bases determines the primary structure/ sequence of amino acids
  • Code is non-overlapping
79
Q

Does breakage of phosphodiester bonds happen during DNA replication ?

A

NO

80
Q

Is the distance between strands in a double helix always the same during DNA replication ?

A

NO as not when they are separate strands

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