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Fundamentals Of Science > DNA To Gene Expression > Flashcards

DNA To Gene Expression Flashcards

1
Q

What bases are pyrimidines?

A

C and T

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2
Q

What bases are purines?

A

A and G

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3
Q

How many hydrogen bonds between bases G andC?

A

3

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4
Q

How many hydrogen bonds between bases A and T?

A

2

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5
Q

DNA structure

A

-Double helix of 2 complementary strands
- composed of nucleotides : sugar, phosphate group and nitrogenous bases

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6
Q

When DNA is replicated what fraction contains the new DNA strand?

A

1/2

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7
Q

DNA replication simplified

A
  • Replication fork formation
  • primer binding
  • elongation
  • termination
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8
Q

Lagging strand is what direction

A

5‘ to 3’ direction

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9
Q

Primer binding

A

-A primer (short RNA piece) binds to a 3’ and of leading strand
Primer binds at starting point for replication

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10
Q

What enzyme unwinds DNA?

A

DNA helicase

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11
Q

Replication progresses in what direction?

A

5’ to 3’ direction

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12
Q

Leading strand is in what direction?

A

3’ to 5’ direction

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13
Q

Elongation stage for leading strand (replication)

A

DNA polymerase create new strands by adding new base pairs

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14
Q

Elongation stage for lagging strand (replication)

A

Begins replication by binding multiple primers

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15
Q

Which strand is DNA synthesised continuosly?

A

Leading strand

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16
Q

On the lagging strand, DNA is synthesised how?

A

In short fragments (Okazaki)

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17
Q

Leading strand synthesised by what enzyme?

A

DNA polymerase

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18
Q

Okazaki fragments are joined by what enzymes?

A

DNA ligases

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19
Q

What enzyme adds pieces of DNA between primers on lagging strand?

A

Another DNA polymerase

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20
Q

In termination what happens to RNA primers?

A

They are removed and replaced with bases

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21
Q

Function of telomerase

A

Adds telomeres at DNA 3’ ends

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22
Q

Termination stage of DNA replication.

A
  • RNA primers removed and replaced
  • Okazaki fragments joined
    -Telomerase adds telomeres
  • parent and complementary strands coil into double helix
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23
Q

Function of topoisomerases

A

Unwind and rewind DNA strands to prevent DNA from getting tangled

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24
Q

RNA structure

A

Single stranded, composed of nucleotides

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25
Q

RNA is synthesised in what direction?

A

5’ to 3’ direction

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26
Q

Transcription steps

A

1 initiation
2 promoter clearance
3 elongation
4 termination

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27
Q

Order of DNA to gone expression

A
  • DNA replication
  • transcription
  • mRNA processing
  • Translation
    Protein folding
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28
Q

Initiation stage of transcription

A
  • RNA polymerase and cofactors unwind and bind to DNA ( at promoter region)

Approx 14 base pairs are exposed each time

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29
Q

Promoter clearance stage in transcription

A
  • Promoter (DNA sequence) signals which DNA strand is transcribed
  • RNA polymerase clears the promoter once the first bond has been synthesised
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30
Q

Elongation stage of transcription

A
  • When RNA strand gets longer
  • one DNA strand is template for RNA synthesis
31
Q

Termination stage of transcription

A
  • release of mRNA from the elongation
32
Q

Template strand for DNA is in what direction?

A

3’ to 5’ direction

33
Q

Introns

A

Non-coding regions that interrupt the gene’s coding sequence

34
Q

mRNA processing steps

A

1 capping at 5’ end
2 addition of a poly-a tail at 3’ end
3 splicing

35
Q

Polyadenylation

A

addition of a poly-a tail at 3’ end

36
Q

Function of capping at 5’ (mRNA processing)

A

Protects 5’ end from degradation and helps position mRNA during protein synthesis

37
Q

Name of cap linked at 5’ (mRNA processing)

A

Methylated-guanosine (7-methyl-G) cap
- (modified guanine (G) nucleotide)

38
Q

What happens at polyadenylation?

A
  • a tail of approximately 200 adenine nucleotides is added to 3’
39
Q

Benefit of polyadenylation

A

Addition of a poly-a-tail (approx.200 adenine nucleotides added at 3’ end)
Helps with efficient translation and stability of mRNA

40
Q

Splicing is?

A

The process of removing introns and rejoining exons of mRNA

41
Q

Exons

A

Coding regions

42
Q

Polypeptide

A

Sequence of amino acids

43
Q

Codons

A

Set of 3 nucleotides for a specific amino acid

44
Q

mRNA vs tRNA

A

mRNA:contains instructions to make a protein
tRNA: responsible for delivering amino acids to ribosomes

45
Q

When tRNA is bound to an amino acid it is called?

A

Aminoacyl-RNA

46
Q

Stages of translation

A

1 initiation
2 elongation
3 termination

47
Q

Initiation stage of translation

A
  • Small submit binds to mRNA and scan it (5’ to 3’ direction) until it encounters the start codon (AUG)
  • when small subunit, mRNA and tRNA are correctly positioned, larger subunit attaches and initiator tRNA binds to ribosome
48
Q

Elongation stage of translation

A
  • Next tRNA with amino acid base, pairs with next codon
    -Peptide bond formed between the 2 amino acids
  • ribosome translocates one codon downstream and initiator tRNA is released
    Cycle repeats until stop codon is reached
49
Q

Start codon for translation

50
Q

Termination stage of translation

A
  • when ribosome reaches stop codon (UAA, UAG or UGA)
  • no tRNAs to stop codons
  • release factors bind and release protein from ribosome
    -Ribosome subunits dissociate from each other
51
Q

Where does folding /refolding of proteins happen?

A

Endoplasmic reticulum

52
Q

Packing of proteins into vesicles happens where?

A

Endoplasmic reticulum further in the Golgi apparatus

53
Q

Glycosylation of proteins happens where?

A

Endoplasmic reticulum /Golgi apparatus

54
Q

Glycosylation of protein is?

A

Attachment of carbohydrates to the backbone of a protein through an enzymatic reaction

55
Q

Gene expression is?

A

Turning on a gene to produce RNA and protein

56
Q

Constitutive genes (describe)

A

Always active, constantly transcribed

57
Q

Example of constitutive genes

A

Ribosome genes

58
Q

Inducible genes (describe)

A

Off unless induced by stimulus

59
Q

Example of inducible genes

A

Glucose transporter proteins in response to insulin

60
Q

Housekeeping genes (describe)

A

Maintain basic cellular function, expressed in all cell types, transcribed at constant rate

61
Q

Example of housekeeping genes

62
Q

Stages of gene expression regulation

A

1 epigenetic control
2 transcriptional control
3 post-transcriptional control
4 translational control
5 post-translational control

63
Q

What happens at replication fork formation?

A

H bonds break unwinding the DNA
Replication progresses in 5’ to 3’ direction
- Leading strand oriented in 3’ to 5’ direction
- lagging strand (follows leading) in 5’ to 3’ direction

64
Q

Function of ER ( endoplasmic reticulum):

A

Folding /folding of proteins
Glycosylation of proteins
Assembly of multi-subunit proteins
Packaging of proteins into vesicles

65
Q

Epigenetic control

A

DNA tightly packed around histones
DNA/histone methylation packs nucleosomes tighter
Histone acetylation loosens nucleosome packing

66
Q

Histone methylation

A

Packs nucleosomes tighter

67
Q

Histone acetylation

A

Loosens nucleosome packing

68
Q

Post-transcriptional control

A

mRNA processing+ Transport from nucleus to cytoplasm + binding to ribosomes
Includes: alternative splicing and control of RNA stability

69
Q

What is alternative splicing?

A

Exon splice together in different combinations to generate different mature MRNAs
Allows production of many proteins using relatively few genes

70
Q

when can post transcriptional control occur?

A

mRNA processing
Transport from nucleus to the cytoplasm
Binding to ribosomes

71
Q

When is translational control regulated?

A

During mRNA AND RIBOSOME BINDING e.g. ferritin

72
Q

What is ferritin?

A

Molecule that is only needed when iron levels are high because its main role is to store the iron

73
Q

Post translational control

A

Modifying protein to affect activity. e.g. reversible, blocking with inhibitors prevents substrate binding

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