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Enzymes > DNA > Flashcards

DNA Flashcards

1
Q

What is the molecule that binds chromatids at the centromere?

A

Cohesin

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2
Q

Maternal and paternal pairs of chromosomes that contain similar but not identical genes are called what?

A

Homologous chromosomes.

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3
Q

What is the chromatin that is complexed with proteins, highly condensed, transcriptionally inactive, and concentrated at the periphery of the cell?

A

Heterochromatin

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4
Q

What is the translucent chromatin that is decondensed, is transcriptionally active, and is near the center of the cell?

A

Euchromatin

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5
Q

What is the highly condensed structure with in the nucleus that contains genes for rRNA?

A

Nucleolus

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6
Q

What is the meshwork of filaments that stabalize the nucelus?

A

Nuclear filaments

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7
Q

The perinuclear space is contiguous with what structure?

A

The ER

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8
Q

How do large molecules pass through the nuclear membrane?

A

Through specific channels

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9
Q

How do small molcules pass through the nuclear membrane?

A

Freely –through small, non-specific opening

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10
Q

What are the top three substances transported across the nuclear membrane?

A

mRNA, proteins, ribosomal subunits

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11
Q

What protein transports mRNA out of the nucleus so that ribosomes may act on it?

A

Ran

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12
Q

Where are ribosomal subunits synthesized? How does this aid in transcriptional regulation?

A

Cytoplasm

Prevents immediate translation

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13
Q

What are the two proteins that are involved in transport into the nucleus?

A

Ran and importin

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14
Q

True or false: the majority of mRNA is transported out of the nucleus by Ran-GTP

A

False–they go through a Ran-independent mechanism

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15
Q

What is the protein that is involved in Ran-independent transport, and is on the cytoplasmic side of the nucleus?

A

Dbp5

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16
Q

True or false: histones are recycled in the processing of new DNA

A

True

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17
Q

Where does DNA polymerase gamma fuction?

A

In the mitochondria

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18
Q

What do DNA polymerases need in order to begin synthesis of a new DNA strand?

A

An RNA primer

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19
Q

What is the direction of DNA synthesis?

A

5’ to 3’ direction

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20
Q

What is the driving factor of DNA replication?

A

Hydrolysis of pyrophosphate

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21
Q

What do DNA helicases do?

A

Unwind the DNA molecule

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22
Q

True or false: origins of replication can only be acted on once during DNA replication?

A

True–there are proteins that ensure this.

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23
Q

What is the action of topoisomerases?

A

Prevent supercoiling of the DNA strand by cutting and re-ligating strands

24
Q

True or false: there are proteins that keep the DNA strands from re-associating once they are unwound

A

True

25
Q

Which DNA polymerase synthesizes a new RNA primer?

A

DNA polymerase alpha

26
Q

An RNA primer has what type of end to it?

A

3’ OH group

27
Q

True or false: DNA polymerases can stay on DNA strands without the need for additional proteins

A

False

28
Q

What is the DNA polymerase that usually transcribes DNA

A

Pol epsilon

29
Q

What are the enzymes that remove the RNA primers?

A

ribonucleases

30
Q

What are the enzymes that bind DNA fragments from okazaki fragments together?

A

DNA ligases

31
Q

What is the action of telomerases?

A

They add additional DNA segments to the end of okazaki fragments so that it can be finished and not result in the shortening of the DNA strand.

32
Q

What is the group that is at the 5’ end of a DNA molecule?

A

Phosphate group

33
Q

What is the group at the 3’ end of a molecule?

A

Hydroxyl

34
Q

What is the type of RNA that is most drastically changed from the original transcription?

A

tRNAs

35
Q

What is the only modification of DNA

A

Methylation of Cytidine

36
Q

Which bases have 3 hydrogen bonds? Which form 2?

A

A and T have 2

C and G have 3

37
Q

Which form of DNA is the most common: B, A or Z

A

B

38
Q

B form DNA helices are what “handed”? What about A? Z?

A

Right handed for B and A

Z is left handed

39
Q

What are the class of molecules that fit exactly on the rungs of the DNA ladder, and cause a distortion of the DNA helix?

A

Intercalcating agents

40
Q

What other structures can DNA be found in, besides the DNA helix?

A

Sequence dependent structures

41
Q

What are the structures that arise from palindromic DNA sequences? RNA?

A

Cruciform structures

Hairpin loops

42
Q

What are the structures that arise from long sequences of pyrimidines (and long purine sequences in the opposing strand)?

A

Triple helical structures

43
Q

What is negative supercoiling?

A

When the DNA is twisted in the direction that unwinds the helix

44
Q

What is positive supercoiling?

A

When the DNA helix is twisted in the direction that winds that helix further

45
Q

What is the action of Type I topoisomerases?

A

Make a single cut in the phosphodiester backbone of a DNA molecule

46
Q

What is the action of Type II topoisomerases?

A

Make a double stranded break

47
Q

Doxorubicn acts on which topoisomerase? What is the consequence of this?

A

topoisomerase II–leads to double stranded breaks and cell death.

48
Q

What are the four types of non-protein producing DNA sequences?

A
  1. Spacer DNA
  2. Introns
  3. Non-protein encoding DNA (for rRNA)
  4. Repetitous DNA sequences
49
Q

What is the type of DNA that does not code for proteins, and is found BETWEEN genes?

A

Spacer sequences

50
Q

What is the type of DNA that does not code for proteins, and is found WITHIN genes?

A

Introns

51
Q

What are pseudogenes?

A

Duplicates of genes that are not transcribed, and are free to mutate.

52
Q

What are the levels of chromatin?

A

11 nm (histone + DNA)
30 nm (nucleosomes together)
300 nm
700 nm

53
Q

DNA and histone complexes are called what?

A

nucleosomes

54
Q

How is the mitochondrial genome more closely related to prokaryotes than to humans (3)?

A
  1. It is circular
  2. Is present as multiple copies within a single mitochondria
    3 .Has a very high gene density
55
Q

What are the four components of a nuclear pore?

A
  1. Nuclear basket
  2. Protein ring in the double membrane
  3. Central transporter on the inside of the ring
  4. filaments on the cytoplasmic side of the ring
56
Q

What is the action of Doxorubicin?

A

Acts on human topoisomerase II, causing double strand breaks in the DNA and cell death.

57
Q

What is the action of Nalidixic acid and ciprofoxacin?

A

They act on topoisomerase II of bacteria, and caused cell death through the introduction of double stranded breaks. These are Abx.

Enzymes (24 decks)

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