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AP Biology > DNA Tech > Flashcards

DNA Tech Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a PCR and its purpose?

A

Polymerase Chain reaction,

  • Used to make multiple copies of a fragment of DNA
  • Can be used to identify DNA at a crime scene or what organism the DNA belongs too
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2
Q

What are the 3 additional molecules needed to produce copies of the DNA in PCR?

A
  • Deoxyribonucleotides
  • Taq polymerase
  • DNA Primers
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3
Q

Describe the process of PCR?

A
  • The sample of DNA is heated to break the hydrogen bonds and separate the parent strand
  • Then the DNA is cooled so that a DNA primer can attach to an end of the DNA
  • Once the DNA primer is placed, Taq polymerase places complimentary deoxyribonucleotides to the parent strands to make two complementary strands
  • All the strands are heated again to separate the complementary strands from the parent strands and produce a new copy of the DNA,
  • This cycle continues and produces copies of the original DNA at a rate of 2^n
  • This process can be done rapidly using a thermocycler which regulates the temperature perfectly for PCR to produce many copies of DNA
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4
Q

Why is Taq polymerase more efficient to use than a normal DNA polymerase in PCR?

A

Taq polymerase is resistant to higher heat so will not denature as easily

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5
Q

Why must the temperature be lowered again after heating up?

A

So the primers can form hydrogen bonds with the template parent strand

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6
Q

What is the function of Taq polymerase?

A

Synthesize new strands of DNA, using the DNA primer as a starting point

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7
Q

What is the DNA primer’s function?

A

To act as a starting point for the Taq polymerase

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8
Q

What is the purpose of gel electrophoresis?

A

To separate fragments of DNA

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9
Q

What process is used to separate DNA molecules?

A

Gel electrophoresis

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10
Q

What is the method for electrophoresis?

A
  • Start with a tray, filled with an aqueous buffer solution,
  • Place a slab of polyacrylamide or agarose gel in the solution with slits for samples of DNA to be added on one side
  • Place two electrodes, one anode (+) and one cathode (-) on either end of the agarose gel, the cathode should be on the side of the DNA samples
  • Connect the electrodes to a current and since DNA is negatively charged, the DNA will start to repel from the cathode and attract to the anode
  • Since the agarose gel is a thick porous solution, the DNA has to weave through pores, the shorter the DNA the further the strand travels in a given time
  • This can be used to separate DNA strands efficiently
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11
Q

Why is DNA negatively charged?

A

There is a negative O connected to the P group of the nucleotides

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12
Q

What is agarose?

A

A polysaccharide gel made from seaweed that is used in electrophoresis

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13
Q

What is reptation?

A

The act of squirming along a smooth-walled narrow passage

- How DNA moves through the agarose gell in electrophoresis

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14
Q

What is a DNA ladder?

A

A set of known DNA fragments with different sizes in base pairs
- The sections of cut DNA in electrophoresis

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15
Q

What is ampicillin?

A

A type of antibiotic

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16
Q

What does CRISPR stand for and what is its purpose?

A

Clustered Regularly Interspaced Short Palindromic Repeats

- A method for DNA editing

17
Q

What is E. coli?

A

Escherichiawhat coli

- A gram-negative bacteria

18
Q

What are gram-negative bacteria?

A

A bacteria resistant to most available antibiotics

19
Q

What is the general function of guide RNA

A

Used as a template for when mRNA is edited

20
Q

What is a plasmid?

A

A small ring of DNA that carries accessory genes separate from the bacteria chromosomes

21
Q

What is bacteria transformation?

A

When a bacteria is edited by a gene or genes from another strain of bacteria

22
Q

Where was CRISPR found?

A

The immune system of bacteria

23
Q

What are CRISPRs?

A

Short repetitive segments of DNA

24
Q

What is a Cas and its function?

A

CRISPR Associated protein, it breaks a section of DNA while being guided by a segment of DNA

25
Q

Explain the process of using CRISPR to edit DNA?

A
  • Scientists create a guide RNA to match the gene they want to edit
  • This guide RNA is attached to Cas9
  • The Cas9 uses the guide RNA to find a section of DNA and cut it in the host
  • Once the DNA is cut, uses homology directive repair by using a template of the DNA to help repair the broken segment, this template can be manipulated to add in a different section of DNA and permanently edit the DNA
  • This can be used to treat genetic diseases and is not limited to humans so is applicable everywhere
26
Q

What is nonhomologous end joining?

A

Repairing damaged DNA by simpling binding the two broken ends to each other,

  • This can miss sections of DNA that have been broken off and therefore is prone to mistakes
  • The resulting gene is normally unusable and turned off
27
Q

What are some issues with CRISPR?

A
  • It is hard to predict the long term effects of CRISPR

- This raises big ethical questions

28
Q

Describe the process of bacteria transformation?

A
  • A restriction enzyme is used to cut a plasmid and a custom section of DNA is inserted in this opening on the plasmid and the DNA is bound into the plasmid using ligation
  • Then the cell membrane of the bacteria needs to partially break for the plasmid to be taken in, holes are made by cooling down and then heating up the bacteria,
  • This heat shock will make breaks in the bacteria for the plasmid to enter, the bacteria cells are cooled down quickly after heating to allow the cell membranes to repair though there is a chance the cell dies,
  • Then the bacteria are cultured to reproduce with the new DNA from the plasmid
  • The DNA from the plasmid can be utilized to create desired proteins, this could give the bacteria resistance to specific antibiotics or allow it to just mass-produce a protein like insulin
29
Q

Why does there need to be a break in the membrane of the bacteria to insert the plasmid in bacteria transformation?

A

DNA is negatively charged so the plasmid cannot diffuse through the cell membrane

30
Q

How is the plasmid bacteria prepared to receive the plasmid in bacteria transformation?

A

Heat shock:

  • Digest the plasmid
  • Create a mixture of the bacteria and digested enzymes and cool them down
  • Then submerge the mixture in a warmer bath and the heat will shock the plasma membrane and break it quickly
  • Then cool down the mixture so the membrane can be healed
  • While the membrane was broken, hopefully, the plasmids entered some of the bacteria cells and can be used by the bacteria to produce proteins from its DNA
31
Q

How can you test that the bacteria absorbed the plasmid in bacteria transformation?

A
  • For the first agar culture, place a sample of the bacteria pre-absorption to make sure the bacteria is alive, if there is growth in the agar culture, the bacteria is alive
  • In the second culture, add the antibiotic and the bacteria pre-absorption to make sure the bacteria is not already resistant to the antibiotic, the bacteria should die and there should be no growth
  • With your sample of bacteria with the plasmids absorbed, add it to a petri dish to make sure that the bacteria is still alive after heat shock, observe some growth of the bacteria to make sure it’s alive
  • Finally, take a sample of the bacteria after absorbing the plasmid and insert it into a petri dish with the antibiotic, if there is bacteria growth it means some of the cells absorbed the plasmid successfully and developed resistance
  • There will likely be fewer bacteria in this last Petri dish because there will be some that died from heat shock and some that did not absorb any plasmids.
32
Q

Why can the bacteria die from heat shock?

A

The cell cannot control what goes in and out with cracks in its membrane, it could easily be invaded by something lethal or lose vital components of the cell

AP Biology (19 decks)

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