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Principles of Molecular Biology > DNA Replication/Transcription > Flashcards

DNA Replication/Transcription Flashcards

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1
Q

DNA replication is an example of _____________ replication

A

Semi-conservative

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2
Q

Which direction does DNA synthesis occur?

A

5’ —> 3’

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3
Q

Which enzyme initiates DNA replication?

A

DNA helicase

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4
Q

How does the enzyme that initiates DNA replication start the process?

A

Separates the paired strand to from a replication fork

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5
Q

What does DNA polymerase do?

A

Synthesises new strand of DNA by adding free DNA nucleotides onto a complementary RNA primer

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6
Q

Why is a RNA primer necessary?

A

Starting place for DNA polymerase

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7
Q

Difference between the leading strand and lagging strand

A

Leading strand will be synthesised continuously whereas the lagging strand cannot as template is limited

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8
Q

What is an Okazaki fragment?

A

A fragment of DNA formed from the lagging strand

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9
Q

What is a sliding clamp?

A

Keeps DNA polymerase firmly attached to the strand but is released when reaches a double strand

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10
Q

Talk through the steps of DNA synthesis

A

DNA primes is used to synthesise short RNA primers
Each primer is extended by DNA polymerase
RNA primer is erased by ribonuclease H and replaced by DNA
DNA ligase joins the 3’ end of new fragment with 5’ of old one if in lagging strand

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11
Q

What is ribonuclease H?

A

An enzyme that erased RNA primer and replaces them with DNA

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12
Q

What is DNA ligase?

A

An enzyme that joins together the phosphate sugar backbone of DNA

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13
Q

Which enzyme produces RNA primers?

A

DNA primase

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14
Q

What does SSBP stand for?

A

Single stranded DNA-binding protein

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15
Q

What do SSBPs do?

A

Maintain unwound parental DNA strands in single-stranded conformation to ease replication fork process

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16
Q

How do SSBPs aid in the lagging strand?

A

Stabilise the ssDNA to prevent formation of short helices –> prevent impediment of DNA synthesis

17
Q

What is transcription?

A

DNA –> mRNA

18
Q

What are the two major steps of gene expression?

A

1) Transcription

2) Translation

19
Q

What does semi-conservative replication mean?

A

Each new double helix is made up of one strand from the parental helix plus one newly synthesised strand

20
Q

Where does transcription occur?

A

In the nucleus

21
Q

Why is it necessary for DNA –> mRNA?

A

mRNA is small enough to leave through a nuclear pore

22
Q

Process of transcription in eukaryotes

A

RNA polymerase II moves stepwise 5’ –> 3’ along the DNA, unwinding the DNA helix just ahead of the active site to produce a copy of mRNA.
Termination of the process occurs when reaches a terminator region

23
Q

What is pre-mRNA?

A

Precursor mRNA is mRNA which hasn’t yet been splice so still contains introns

24
Q

What is the initiator step in transcription?

A

RNA polymerases bind to promoter region

25
Q

What is the elongation step in transcription?

A

When an mRNA transcript of DNA is being yielded

26
Q

What is the termination step in transcription?

A

When RNA polymerase encounters a terminator region which promotes the dissociation of RNA polymerase

27
Q

What do general transcriptions factors aid?

A
  • Positioning of promoter
  • Pulling apart two strands of DNA for transcription
  • Release RNA polymerase from promoter –> start transcribing
28
Q

What carries out RNA splicing?

A

Spliceosome

29
Q

What is a spliceosome made up of?

A

snRNAs with protein

– five snRNPs and numerous proteins make up the core

30
Q

What do spliceosomes do?

A

Remove intron sequences from pre-mRNA

31
Q

What is an advantage of RNA splicing?

A

Splicing occurs in different ways which means that the same gene is able to produce different proteins
–> increases coding potential of the genome

32
Q

How the is the coding potential of the genome increased?

A

RNA splicing

Principles of Molecular Biology (12 decks)

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