Genetic discovery and processes Flashcards

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1
Q

Who discovered that DNA was used for genetic material instead of proteins?

A

Hershey and Chase

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2
Q

What virus was used in the Hershey-Chase experiment?

A

Bacteriophage/ phages, is a virus that infects bacteria by injecting it with DNA

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3
Q

What are the steps to the Hershey-Chase experiment?

A
  • A phage was produced in a medium of 35S amino acid, which radioactively labeled the protein shell of the phage,
  • When the phage injected its DNA into a bacteria, the phages that reproduced had no radioactive labeling
  • The phage protein shells are removed from the outside of the cell by vigorous shaking
  • A second phage was produced in a medium of 32P deoxyribonucleotides, this radioactively labeled the DNA,
  • When this phage injected its DNA into the bacteria, the phage that reproduced had the same radioactive labeling,
  • The phage protein shells are again shaken from the outside of the cell
  • This proves that genetic information is stored in DNA
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4
Q

What is the basic structure of a phage?

A
  • Protein shell

- Holds DNA inside

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5
Q

What are the two mediums the phages were produced in?

A
  • 35s (protein)

- 32p (nucleotide)

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6
Q

What protein unwinds DNA and what bonds are broken?

A

Helicase breaks the hydrogen bonds between base pairs in a double helix

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7
Q

What is the enzyme that adds new nucleotides to DNA and where does it add them?

A

Polymerase adds DNA on a free 3’ end of a growing strand

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8
Q

What are the leading and lagging strands in DNA replication?

A
  • Leading strand is added to a free 3’ end on a strand, DNA is placed from 5’ to 3’
  • Lagging strand is also added to a free 3’ end of a strand, but because the template strand is read 5’->3’ polymerase cannot function continuously
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9
Q

How does DNA get placed on the 3’->5’ direction (lagging strand)?

A
  • An RNA primer is placed further down the template strand by RNA primase
  • Polymerase III then places DNA on the new RNA primers 3’ end towards OoR
  • The new DNA placed and the RNA primer is called an Okazaki fragment
  • A polymerase I replaces the polymerase III and places DNA where the RNA primer was placed in the previous cycle,
  • DNA ligase then connects the new DNA placed by DNA polymerase III with the DNA placed by the DNA polymerase I using phosphodiester bonds
  • The cycle restarts (DISCONTINUOUS)
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10
Q

What is the function of RNA primase?

A

An enzyme that places the RNA primer in DNA synthesis

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11
Q

What is the function of Polymerase III?

A

An enzyme that places DNA from the 3’ end of an RNA primer

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12
Q

What is the function of Polymerase I?

A

An enzyme that replaces polymerase III and then replaces RNA primer with DNA

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13
Q

What is the function of DNA ligase?

A

An enzyme that creates phosphodiester bonds between two fragments of DNA to make a single fragment

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14
Q

What strand of DNA synthesizes continuously?

A

The leading strand

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15
Q

What strand of DNA synthesizes discontinuously?

A

The lagging strand

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16
Q

How does the DNA unwind in DNA replication?

A

Helicase enzymes break the hydrogen bonds between bases and the strands of DNA straighten out and extend,

  • One strand is a 3’ Carbon side
  • The other is a 5’ Carbon side
17
Q

What is DNA polymerase?

A

An enzyme that places DNA and connects individual nucleotides to each other to make a DNA molecule

18
Q

What is the lagging strand in DNA synthesis?

A

A strand that is replicated in short fragments,

  • MADE in the 3’ -> 5’ direction
  • Parent is read in the 5’ -> 3’ direction
19
Q

What is the leading strand in DNA synthesis?

A

A strand that is MADE continuously in the 5’ -> 3’ direction

- Parent strand is read in the 3’ -> 5’

20
Q

What is an Okazaki fragment?

A

Small fragments of DNA produced on the lagging strand during DNA replication

  • Includes RNA primer and newly placed DNA from polymerase III
  • fragment between two RNA primers
21
Q

What places the RNA primer?

A

Primase,

- Uses the parent strand as a template to make an RNA complementary fragment

22
Q

What is RNA primer?

A

A short segment of RNA that acts as a starting point for a new DNA strand

23
Q

What is the replication fork?

A

A Y-shaped region on a replicating DNA molecule where new strands are growing

24
Q

What is the function of single-strand binding proteins in DNA replication?

A

A protein that binds to and stabilizes unwound DNA until it is used as a template
- Binds near the start of the replication fork

25
Q

What is topoisomerase/gyrase?

A

Proteins that untangle DNA before the replication fork

- Does so by breaking the DNA and then repairing it once they untangle

26
Q

What is the difference between topoisomerase and gyrase?

A

Topoisomerase is found in eukaryotes while gyrase is found in prokaryotes

27
Q

What is the origin of replication (OoR)?

A

A segment of DNA where the reading of the parent strand begins bidirectionally

  • Site where DNA replication starts
  • Consists of specific nucleotide sequences
28
Q

What is telomerase?

A

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells

29
Q

What is nucleotide excision repair?

A

Enzymes cutting and replacing damaged stretches of DNA

30
Q

What is nuclease?

A

An enzyme that cuts DNA or RNA

- Does this by removing a few bases or hydrolyzing the DNA or RNA completely into its component nucleotides