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BI1014: Biological Chemistry > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

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1
Q

What role do nucleic acids play in the body?

A

They are the set of instructions for the body.

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2
Q

Why are genetic diseases a problem?

A

1-2% of newborns have a genetic disease and are the cause of half of all childhood deaths.

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3
Q

What is the process of converting DNA into RNA?

A

Transcription

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4
Q

What is the process of converting RNA into protein?

A

Translation

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5
Q

Why are DNA and RNA different?

A

DNA is designed to be more stable to act as long term storage. RNA is more accessible for coding for proteins.

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6
Q

What makes up a nucleotide?

A

Deoxyribose.
Nitrogenous base.
Phosphate group.

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7
Q

What type of sugar is deoxyribose?

A

A pentose sugar.

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8
Q

Which of the bases are purines?

A

Adenine and Guanine are purines.

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9
Q

Which of the bases are pyrimidines?

A

Cytosine and thymine are pyrimidines.

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10
Q

What is the difference between purines and pyrimidines?

A

Purines have a 2 ring structure; pyrimidines have a 1 ring structure.

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11
Q

What is a nucleoside?

A

Formed when a base is linked to the 1’ carbon of a deoxyribose/ribose molecule. Essentially a nucleotide lacking a phosphate group.

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12
Q

How would you name a nucleoside made up of deoxyribose and adenine?

A

Deoxyadenosine

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13
Q

What is a nucleotide?

A

A nucleoside with one or more phosphate groups linked to the 5’ carbon.

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14
Q

What are the 4 nucleotides in DNA?

A

Deoxyadenosine monophosphate.
Deoxycytosine monophosphate.
Deoxyguanosine monophosphate.
Deoxythymidine monophosphate.

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15
Q

Where is single-stranded DNA found?

A

Only in bacteriophages.

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16
Q

How many bonds form between Guanine and Cytosine?

A

3 hydrogen bonds.

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17
Q

Is DNA a right-handed or left-handed helix?

A

Right-handed helix.

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18
Q

Where is the sugar-phosphate backbone in relation to the nitrogenous bases?

A

The sugar-phosphate backbone is on the outside.

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19
Q

How are the strands held together?

A

By base pairing. Hydrophobic interactions between adjacent bases also occurs - this is known as base-stacking.

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20
Q

How tightly coiled is the helix of DNA?

A

The helix makes 1 turn every 3.4nm.

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21
Q

How many base pairs are there per turn of the helix, in DNA?

A

10 base pairs per turn.

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22
Q

How do the major and minor grooves of the DNA helix impact its properties?

A

Minor bases are more hidden; major bases are more exposed.

Sugar-phosphate backbones are closer together at minor grooves.

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23
Q

What are the 3 conformations of DNA?

A

A-DNA, B-DNA AND Z-DNA.

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24
Q

What is the commonest conformation of DNA?

A

B-DNA, it makes up nearly all cellular DNA.

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25
Q

How is A-DNA formed?

A

Forms when DNA is dehydrated.

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26
Q

What are the structural differences of Z-DNA?

A

12bp per turn (A-DNA 11bp, B-DNA 10bp).
Left-handed helix.
Zig-zag sugar-phosphate backbone.

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27
Q

How is supercoiling caused?

A

Either by underwinding (generating negative supercoils) or overwinding (generating positive supercoils) the DNA.

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28
Q

How is DNA supercoiled in vivo?

A

Negatively supercoiled.

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29
Q

How do you denature DNA?

A

Heat the DNA to 70-100°C.

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30
Q

What happens when DNA is denatured?

A

Hydrogen bonds between nitrogenous bases are broken allowing the strands to separate.

31
Q

If allowed to cool, what will happen to DNA strands after denaturation?

A

The strands will slowly reanneal.

32
Q

How can denaturation be monitored? Why is this possible?

A

Measure the UV light absorbance at a 260nm wavelength.

Single stranded DNA absorbs more UV than the same mass of double stranded DNA.

33
Q

How can the temperature of DNA denaturation be increased?

A

Increasing Guanine and Cytosine content - more hydrogen bonds need to be broken.
Increasing the presence of cations - these reduce repulsion between negatively charged phosphate groups.

34
Q

How do DNA and RNA differ?

A

Deoxyribose VS Ribose.
Thymine VS Uracil.
Double stranded VS Single stranded.

35
Q

Why is RNA more reactive than DNA? Think about the structure of the pentose sugar.

A

The OH on Carbon-2 (instead of just H) makes it more reactive.

36
Q

Define genome.

A

The genetic material contained in an organism, cell, virus or organelle.

37
Q

Define chromatin.

A

DNA-protein complex present in the nuclei of eukaryotic cells during interphase.

38
Q

How do bacterial chromosomes differ from eukaryotic chromosomes?

A

Usually just have 1 CIRCULAR chromosome.

39
Q

How is so much DNA stored within E. coli?

A

The DNA is supercoiled and bound to protein to form a nucleoid.

40
Q

How does a nucleoid differ from a nucleus?

A

A nucleoid lacks a membrane.

41
Q

What are plasmids?

A

These are accessory circular DNA molecules ranging from 1kb to 400kb in size.

42
Q

What is are some very important genes that may be carried by a plasmid?

A

Genes for antibiotic resistance.

43
Q

How is RNA multifunctional?

A

It can carry information (mRNA).
Act as a transporter (tRNA).
Act structurally (ribosomal RNA).
Act as a regulator for gene expression (micro RNA).

44
Q

What is repetitive DNA?

A

Non-coding sequences of DNA present.

45
Q

What makes up chromatin?

A

Heterochromatin (inactive) and euchromatin (active).

46
Q

How do you calculate packing ratio?

A

Packing ratio = Length of DNA/Length of structure DNA packed into

47
Q

What are nucleosomes?

A

Protein particles that act as a spool. Can be thought of as the subunits of chromosomes and chromatin.

48
Q

What makes up the mitotic chromosome scaffold and what is its function?

A

It is made up of non-histone proteins and anchors long loops of nucleosomes.

49
Q

What is the function of topoisomerase II?

A

An enzyme that can remove supercoils.

50
Q

How does acetylation of histones affect transcription?

A

DNA associated with acetylated histones is more readily transcribed. This is because adding an acetyl group weakens interactions between histones and DNA.

51
Q

What is the initiation codon?

A

AUG

52
Q

What are the 3 termination codons?

A

UGA, UAA and UAG.

53
Q

What is the region between an initiation codon and a termination codon known as?

A

The open-reading frame.

54
Q

What sequence is found at the 3’ end of tRNA?

A

CCA

55
Q

What is base wobble?

A

The ability of some bases at the 5’ end of an anticodon to pair with more than one base at the 3’ end of a codon.

56
Q

What are the group of enzymes that link tRNAs to amino acids.

A

Aminoacyl-tRNA synthetases.

57
Q

What organelles perform translation?

A

Ribosomes

58
Q

What size ribosomes are found in human cells?

A

80S

59
Q

In what direction is mRNA read?

A

5’ to 3’

60
Q

What are the 3 stages of translation?

A

Initiation.
Elongation.
Termination.

61
Q

What is the initiation stage of translation?

A

The binding of mRNA and the first tRNA, and assembly of the ribosome.

62
Q

What is the elongation stage of translation?

A

Addition of amino acids to the growing peptide.

63
Q

What is the termination stage of translation?

A

Dissociation of the completed protein from the ribosome.

64
Q

What are the 3 ways gene expression can be regulated?

A

Regulating transcription.
Regulating translation.
Regulating RNA processing.

65
Q

What is an operon?

A

A cluster of several genes transcribed into a single m RNA. It allows the regulator of a single promotor to control the production of multiple proteins.

66
Q

Why is the origin of replication rich in Adenine and Thymine?

A

Because these organic bases only form 2 hydrogen bonds between them, so it’s easier to split the two strands.

67
Q

How many origins of replication are found in prokaryotes? How does this differ to eukaryotes?

A

Only 1 in prokaryotes. Many in eukaryotes in order to save time.

68
Q

Which enzymes synthesise DNA?

A

DNA polymerases.

69
Q

What is needed for DNA polymerase to synthesise DNA?

A

The 4 deoxynucleoside triphosphates.
A template.
A primer.

70
Q

What are the 4 fundamental features of DNA replication?

A

Semiconservative.
Bidirectional.
Semi-discontinuous.
Dependent on RNA primers.

71
Q

What is the coding strand?

A

DNA strand with the same base sequence as the RNA being synthesised - excluding T for U.

72
Q

What is the non-coding strand?

A

The template strand for RNA synthesis. Complementary to the RNA molecule.

73
Q

What is the terminator?

A

DNA sequence that signals the end of a gene. This is where RNA polymerase dissociates from DNA.

Also a cyborg assassin played by Arnold Schwarzenegger.

74
Q

What is the terminator?

A

DNA sequence that signals the end of a gene. This is where RNA polymerase dissociates from DNA.

Also a cyborg assassin played by Arnold Schwarzenegger.

BI1014: Biological Chemistry (7 decks)

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