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Biomedical Sciences & Oral Ecosystems I > DNA > Flashcards

DNA Flashcards

1
Q

A polymer of deoxyribonucloside mono-phosphates covalently linked by a 3’⇢5’

  1. Hydrogen bond
  2. Phosphodiester bond
  3. Peptide bond
A

Phosphodiester bond

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2
Q

The structure of DNA has the following, which is not an answer

  1. Double helix with antiparallel chains
  2. Major groove which binds regulatory proteins
  3. minor grove which binds drugs
  4. sugar ribose backbone
A

sugar ribose backbone, because it is a sugar phosphate backbone

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3
Q

Which DNA base pairing will need a lot of heat to separate them

  1. AT
  2. GC
A

GC - because it has 3 hydrogen bonds vs AT with 2 hydrogen bonds

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4
Q

What is the temperature at which ½ of the helical structure is lost

  1. heating temperature hm
  2. melting temperature Tm
  3. Vaporization temperature
A

Melting temperature Tm

At temperatures above Tm, DNA is present as a single strand.

Graph: vertical ( absorbance of UV), horizontal (temperature). More UV absorbed to break helical structure= high temperature

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5
Q

Which structural form of the double helix of DNA is the most common?

  1. B-DNA
  2. Z-DNA
  3. A-DNA
A

B-DNA

A-DNA; right handed helix usually present with non physiological conditions

Z-DNA; left handed helix. Present with methylation and modification of DNA

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6
Q

Eukaryotes have the following characteristics, which one is incorrect?

  1. Single stranded, circular chromosome associated with non-histone proteins
  2. linear double stranded DNA molecule associated with histone and non histone proteins
  3. closed circular DNA in mitochondria of eukaryotes
  4. All the above
A

ingle stranded, circular chromosome associated with non-histone proteins. This is a prokaryote

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7
Q

Small circular extra chromosomal DNA molecules are called

  1. Histones
  2. Plasmids
  3. Prions
  4. Myloid linkage
A

Plasmids

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8
Q

Enzymes used for DNA synthesis are called

  1. Ribonucleases
  2. DNA polymerases
  3. deoxyribonucleases
  4. All the above
A

DNA polymerases

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9
Q

What are the order of the steps in prokaryotic DNA synthesis

  1. RNA primer
  2. Separation of the two complementary strands
  3. DNA ligase
  4. Chain elongation
  5. Excision of RNA primers and replacement by DNA
  6. Formation of the replication fork
  7. Direction of DNA replication
A
  1. Separation of the two complementary strands
  2. Formation of the replication fork
  3. Direction of DNA replication
  4. RNA primer
  5. Chain elongation
  6. Excision of RNA primers and replacement by DNA
  7. DNA ligase
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10
Q

What base pairs are at the origin of replacement site

  1. AC pairs
  2. AT pairs
  3. GC pairs
  4. GA pairs
A

AT pairs because they are easier to melt

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11
Q

True or False

Eukaryotes have multiple origin site of replication for rapid replication because they have bigger DNA, prokaryotes have one origin site or replication because it has smaller DNA

A

True

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12
Q

These 2 things happen at this step of prokaryotic DNA synthesis

  1. As the 2 strands unwind and separate they form a V where active synthesis occurs
  2. Replication of dsDNA is bidirectional generating a replication bubble
A

Formation of the replication fork

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13
Q

Binds to origin and causes the AT rich regions to melt

A

DnaA protein

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14
Q

unwinds the double helix

A

DNA helicases

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15
Q

ssDNA binding proteins

A

keeps the strands apart and protect DNA from nucleases that degrade ssDNA

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16
Q

Cut and rejoin one strand of double helix to remove supercoils

A

Topoisomerase I

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17
Q

cuts and rejoins both strands e.g. DNA gyrase

A

Topoisomerase II

18
Q

The strand that is being copied in the direction of the advancing replication fork which is synthesized continuously

A

Leading strand

19
Q

Strand being copied in the opposite direction to the direction of the replication fork, it is synthesized discontinuously

A

lagging strand

this has okazaki strands

20
Q

True or False

DNA polymerases read the parental strand in the 3’⇢5’ direction therefore synthesis happens in the 5’⇢3” direction

A

True

21
Q

T/F

DNA polymerases require and RNA primer (`10nucleotide) with a free OH on the 3’ end

A

True

  • RNA primer is catalyzed by primase
  • RNA polymerases do not need a primer
22
Q

Which polymerase is responsible for chain elongation during the prokaryotic DNA synthesis

  1. DNA polymerase III
  2. DNA Polymerase I
  3. RNA polymerase IV
  4. DNA Polymerase II
A

DNA Polymerase III

  • highly processive, it remains bound to template by its beta subunit as it moves along
  • it has 3’to5’ exonuclease activity to correct mismatching bases. Goes backwards and corrects mis-matches
23
Q

Which polymerase is responsible for excising RNA primers and filing the gap during the prokaryotic DNA synthesis

  1. DNA polymerase III
  2. DNA Polymerase I
  3. RNA Polymerase IV
  4. DNA Polymerase II
A

DNA Polymerase I

24
Q

This makes the final phosphodiester linkage between the 5’ phosphate on the DNA chain synthesized by DNA pol III and the 3’ OH on the chain made by DNA pol I

A

DNA Ligase

25
Q

True or False

In eukaryotic DNA replication, RNA primers are removed by RNase rather than DNA polymerase I

A

True

26
Q

Stage in interphase where a cell prepares to initiate DNA synthesis, biosynthesis also occurs here

A

G1

27
Q

Stage in interphase where a cell DNA content doubles, DNA synthesis occurs here

A

S phase

28
Q

Stage in interphase where a cell where biosynthesis for mitosis occurs, more DNA synthesis happens here

A

G2

29
Q
  • If you remove growth factors, cells will end up in this phase of interphase
  • this is where cells are sent to reactivate
  • Nerve cells exit this cell cycle stage permanently
  • Cells that have ceased division
A

G0

30
Q

Phase of the cell cycle where cell division happends

A

mitosis

31
Q
  • DNA polymerase that contains primase
  • initiates DNA synthesis
A

Polymerase Alpha

32
Q

DNA polymerase that elongates the okazaki fragments of the lagging strand

A

DNA Polymerase delta

33
Q

DNA polymerase that elongates the leading strand

A

DNA polymerase epsilon

34
Q
  • complexes of noncoding DNA plus proteins located at the ends of linear chromosomes
  • maintain structural integrity of the chromosomes, preventing attach by nucleases
  • Allow repair enzymes to distinguish between a true end from a break in dsDNA
  • Consist of several thousand tandem repeats of noncoding AGGGTT paired with a complementary region of Cs and As
  • Shorten with every successive division
A

Telomeres

35
Q

This enzyme maintains telomeric length in stem cells and cancer cells

A

telomerase - keeps replacing the telomere region

36
Q

Enzyme that synthesizes DNA from RNA

A

Reverse Transcriptase

37
Q
  • Basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes
  • Eukaryotic DNA is associated with these tightly bound basic proteins
A

Histones

38
Q

Histones + DNA

A

Nucleosomes

Each chromosome contains a long molecule of DNA, which must fit into the cell nucleus. To do that, the DNA wraps around complexes of histone proteins, giving the chromosome a more compact shape

39
Q

DNA damage can happen by the following which is not correct?

  1. Hydrolysis - lose amino group and get H2O
  2. Oxidation - loss of electrons
  3. Methylation - different parts of bases can be methylated
  4. UV light
  5. Ionizing radiation
  6. All the above
A

All the above

40
Q

This DNA damage leads to the formation of pyrimidine dimers & thymine dimers ( thymines bond together)

A

UV light

41
Q

This type of DNA damage leads to strand breaks in the DNA

A

Ionizing radiation

Biomedical Sciences & Oral Ecosystems I (4 decks)

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