DNA Flashcards Preview

Enzymes > DNA > Flashcards

Flashcards in DNA Deck (57):
1

What is the molecule that binds chromatids at the centromere?

Cohesin

2

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

Homologous chromosomes.

3

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

Heterochromatin

4

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

Euchromatin

5

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

Nucleolus

6

What is the meshwork of filaments that stabalize the nucelus?

Nuclear filaments

7

The perinuclear space is contiguous with what structure?

The ER

8

How do large molecules pass through the nuclear membrane?

Through specific channels

9

How do small molcules pass through the nuclear membrane?

Freely --through small, non-specific opening

10

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

mRNA, proteins, ribosomal subunits

11

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

Ran

12

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

Cytoplasm
Prevents immediate translation

13

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

Ran and importin

14

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

False--they go through a Ran-independent mechanism

15

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

Dbp5

16

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

True

17

Where does DNA polymerase gamma fuction?

In the mitochondria

18

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

An RNA primer

19

What is the direction of DNA synthesis?

5' to 3' direction

20

What is the driving factor of DNA replication?

Hydrolysis of pyrophosphate

21

What do DNA helicases do?

Unwind the DNA molecule

22

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

True--there are proteins that ensure this.

23

What is the action of topoisomerases?

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

24

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

True

25

Which DNA polymerase synthesizes a new RNA primer?

DNA polymerase alpha

26

An RNA primer has what type of end to it?

3' OH group

27

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

False

28

What is the DNA polymerase that usually transcribes DNA

Pol epsilon

29

What are the enzymes that remove the RNA primers?

ribonucleases

30

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

DNA ligases

31

What is the action of telomerases?

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

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

Phosphate group

33

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

Hydroxyl

34

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

tRNAs

35

What is the only modification of DNA

Methylation of Cytidine

36

Which bases have 3 hydrogen bonds? Which form 2?

A and T have 2
C and G have 3

37

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

B

38

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

Right handed for B and A
Z is left handed

39

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

Intercalcating agents

40

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

Sequence dependent structures

41

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

Cruciform structures
Hairpin loops

42

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

Triple helical structures

43

What is negative supercoiling?

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

44

What is positive supercoiling?

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

45

What is the action of Type I topoisomerases?

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

46

What is the action of Type II topoisomerases?

Make a double stranded break

47

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

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

48

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

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

49

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

Spacer sequences

50

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

Introns

51

What are pseudogenes?

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

52

What are the levels of chromatin?

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

53

DNA and histone complexes are called what?

nucleosomes

54

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

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

55

What are the four components of a nuclear pore?

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

What is the action of Doxorubicin?

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

57

What is the action of Nalidixic acid and ciprofoxacin?

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