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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
How is A-DNA formed?
Forms when DNA is dehydrated.
26
What are the structural differences of Z-DNA?
12bp per turn (A-DNA 11bp, B-DNA 10bp). Left-handed helix. Zig-zag sugar-phosphate backbone.
27
How is supercoiling caused?
Either by underwinding (generating negative supercoils) or overwinding (generating positive supercoils) the DNA.
28
How is DNA supercoiled in vivo?
Negatively supercoiled.
29
How do you denature DNA?
Heat the DNA to 70-100°C.
30
What happens when DNA is denatured?
Hydrogen bonds between nitrogenous bases are broken allowing the strands to separate.
31
If allowed to cool, what will happen to DNA strands after denaturation?
The strands will slowly reanneal.
32
How can denaturation be monitored? Why is this possible?
Measure the UV light absorbance at a 260nm wavelength. | Single stranded DNA absorbs more UV than the same mass of double stranded DNA.
33
How can the temperature of DNA denaturation be increased?
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
How do DNA and RNA differ?
Deoxyribose VS Ribose. Thymine VS Uracil. Double stranded VS Single stranded.
35
Why is RNA more reactive than DNA? Think about the structure of the pentose sugar.
The OH on Carbon-2 (instead of just H) makes it more reactive.
36
Define genome.
The genetic material contained in an organism, cell, virus or organelle.
37
Define chromatin.
DNA-protein complex present in the nuclei of eukaryotic cells during interphase.
38
How do bacterial chromosomes differ from eukaryotic chromosomes?
Usually just have 1 CIRCULAR chromosome.
39
How is so much DNA stored within E. coli?
The DNA is supercoiled and bound to protein to form a nucleoid.
40
How does a nucleoid differ from a nucleus?
A nucleoid lacks a membrane.
41
What are plasmids?
These are accessory circular DNA molecules ranging from 1kb to 400kb in size.
42
What is are some very important genes that may be carried by a plasmid?
Genes for antibiotic resistance.
43
How is RNA multifunctional?
It can carry information (mRNA). Act as a transporter (tRNA). Act structurally (ribosomal RNA). Act as a regulator for gene expression (micro RNA).
44
What is repetitive DNA?
Non-coding sequences of DNA present.
45
What makes up chromatin?
Heterochromatin (inactive) and euchromatin (active).
46
How do you calculate packing ratio?
Packing ratio = Length of DNA/Length of structure DNA packed into
47
What are nucleosomes?
Protein particles that act as a spool. Can be thought of as the subunits of chromosomes and chromatin.
48
What makes up the mitotic chromosome scaffold and what is its function?
It is made up of non-histone proteins and anchors long loops of nucleosomes.
49
What is the function of topoisomerase II?
An enzyme that can remove supercoils.
50
How does acetylation of histones affect transcription?
DNA associated with acetylated histones is more readily transcribed. This is because adding an acetyl group weakens interactions between histones and DNA.
51
What is the initiation codon?
AUG
52
What are the 3 termination codons?
UGA, UAA and UAG.
53
What is the region between an initiation codon and a termination codon known as?
The open-reading frame.
54
What sequence is found at the 3' end of tRNA?
CCA
55
What is base wobble?
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
What are the group of enzymes that link tRNAs to amino acids.
Aminoacyl-tRNA synthetases.
57
What organelles perform translation?
Ribosomes
58
What size ribosomes are found in human cells?
80S
59
In what direction is mRNA read?
5' to 3'
60
What are the 3 stages of translation?
Initiation. Elongation. Termination.
61
What is the initiation stage of translation?
The binding of mRNA and the first tRNA, and assembly of the ribosome.
62
What is the elongation stage of translation?
Addition of amino acids to the growing peptide.
63
What is the termination stage of translation?
Dissociation of the completed protein from the ribosome.
64
What are the 3 ways gene expression can be regulated?
Regulating transcription. Regulating translation. Regulating RNA processing.
65
What is an operon?
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
Why is the origin of replication rich in Adenine and Thymine?
Because these organic bases only form 2 hydrogen bonds between them, so it's easier to split the two strands.
67
How many origins of replication are found in prokaryotes? How does this differ to eukaryotes?
Only 1 in prokaryotes. Many in eukaryotes in order to save time.
68
Which enzymes synthesise DNA?
DNA polymerases.
69
What is needed for DNA polymerase to synthesise DNA?
The 4 deoxynucleoside triphosphates. A template. A primer.
70
What are the 4 fundamental features of DNA replication?
Semiconservative. Bidirectional. Semi-discontinuous. Dependent on RNA primers.
71
What is the coding strand?
DNA strand with the same base sequence as the RNA being synthesised - excluding T for U.
72
What is the non-coding strand?
The template strand for RNA synthesis. Complementary to the RNA molecule.
73
What is the terminator?
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
What is the terminator?
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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