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Molecular Biology > Ch 9 > Flashcards

Ch 9 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Centromere

A

Segment of each eukaryotic chromosome that functions during cell division as an attachment point for proteins that link the chromosome to the mitotic spindle

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2
Q

Telomeres

A

Sequences at the ends of eukaryotic chromosomes that add stability by protecting the ends from nucleares and providing unique mechanisms for the faithful replication of linear DNA molecules

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3
Q

Plasmids

A

Smaller circular DNA molecules that are few in the cytosol

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4
Q

DNA supercooling

A

Coiling of DNA upon itself, generally as a result of bending, under winding, or over winding of the DNA helix

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5
Q

Relaxed DNA

A

No net cooling of the DNA axis upon itself

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6
Q

DNA topology

A

Continuous deformations include conformational changes due to stretching, thermal motion, or interaction with proteins or other molecules

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7
Q

Closed circular DNA

A

Underwound circular DNA with no breaks in either strand

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8
Q

Linking number(LK)

A

Number of times one closed circular DNA strand is wound about another, the number of topological links holding the circles together

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9
Q

LK for right handed helix

A

Is +, stands inter wound in helix

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10
Q

LK for left handed helix

A

(-)

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11
Q

LK for relaxed DNA

A

LK = #of no/(# no/helical turn)

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12
Q

Superhelical density

A

A measure of the # of turns removed relative to the number of turns present in relaxed DNA

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13
Q

Negative supercoiling

A

The twisting of a helical(coiled) molecule on itself to form a right handed supercoil

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14
Q

Positive supercoiling

A

The twisting of a helical(coiled) molecule on itself to form a led-handed supercoil

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15
Q

Toposiomerases

A

Different forms of a covalently closed, circular DNA molecule that differ only in their linking number

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16
Q

Plectonemic supercoiling

A

A structure in a molecular polymer that has a net twisting of strands about each other in some simple and regular way

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17
Q

Solenodial supercoiling

A

A model for the arrangement of nucleosomes in the 30nm filament in which the nucleosome array assumes a spiral shape, w/the flat sides of adjacent nucleosomes next to each other

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18
Q

Type I topoisomerase

A

Break one of the two DNA strands, pass the unbroken strand through the break, and lígate the broken ends (LK changes in increments of 1)

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19
Q

Type II topoisomerase

A

Break both strands of DNA, change LK in increments of 2

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20
Q

SMC proteins

A

Promote chromosome condensation by creating physical content between segments of DNA that may otherwise be distant from each other on the chromosome, or even in a different chromosome

21
Q

Cohesion

A

SMC proteins that link sister chromatids immediately after chromosomal replication & keep them together as the chromosomes condense to metaphase

22
Q

Condensins

A

SMC proteins that facilitate chromosomal condensation

23
Q

How does the length of a chromosome, either prokaryotic or eukaryotic, compare to the overall length of the cell?

A

Chromosomes are much longer than the biological packages-the cells, organelles, or viral particles
-the nucleus is about 1/3 the size of the cell

24
Q

How do centromeres differ between higher order and lower order eukaryotes?

A

The centromere sequences of higher eukaryotes are much longer and contain regions of simple sequence DNA consisting of tandem copies of one or a few 5-10 bp

25
Q

What happens at the centromere at mitosis?

A

Centromeres aren’t always in the middle of the chromosome

However usually: proteins attach to the centromere as an attachment point to the mitotic spindle at metaphase; centromeres play a key role in stabilizing chromosome segregation during cell division

26
Q

What proteins attach to the centromere that aid in the separation of sister chromatids?

A

Kinetochore microtubules attach to the centromere to aid in separation during mitosis

27
Q

Key function of telomeres:

A

Solve end replication problem in linear DNA

  • telomeres are noncoding
  • telomerase has to complimentary base pair with telomere so if the sequence does not match the telomerase then it will not work
28
Q

How does telomerase elongate DNA strand?

A

Telomerase uses own RNA template to extend DNA molecule

29
Q

How does telomerase differ from DNA polymerase?

A

Telomerases allow replication in telomeres

30
Q

Is genetic information found in places other than the nucleus in eukaryotes?

A

Yes
Mitochondria(functional RNA, tRNA, and rRNA)
Chloroplast contain their own DNA
-these are both circular

31
Q

What genes do we find on mitochondrial DNA, and how is that these genes offer supporting evidence to the endosymbiotic theory?

A
  • 13 protein encoding genes
  • mitochondrial DNA codes for mitochondrial tRNAs, rRNAs and a few other mitochondrial proteins; more than 95% of mitochondrial proteins are encoded by nuclear DNA; mitochondria divides when the cells divide; their DNA is replicated before and during cell division
  • much smaller than nuclear DNA
32
Q

Is supercoiling necessary?

A

Yes, this is how DNA gets compacted

33
Q

DNA gyrase

A

Uses ATP to drive key conformational changes that counteract the thermodynamically unfavorable introduction of negative supercoils

  • only topoisomerase that introduces negative supercoils
  • cleaves both strands of DNA
  • only found in bacteria
34
Q

Underwound DNA gave how many base pairs per turn?

A

More than 10.5 bp/turn and it is negatively supercoiled(right handed helix)

-more accessible to proteins

35
Q

Overwound DNA has how many base pairs per turn?

A

Fewer than 10.5 bp/turn and is positively supercoiled (left)

36
Q

Topoisomerase II in E.coli

A

DNA gyrase

Function: works ahead of the helicase to relieve the strain of the supercoils

37
Q

Topoisomerase IV in E.coli

A

Unlinks chromosomes and then reconnects the chromosomes

38
Q

Which class of topoisomerase require ATP?

A

DNA gyrase

39
Q

What supercoiled state is DNA usually kept in in the cell and why?

A

DNA is maintained in a negatively supercoiled state because because cellular processes such as transcription and replication cause additional torsional strain

-more accessible to proteins

40
Q

What is an example of an organism that does not have negatively supercoiled DNA?

A

Thermophiles

-keep DNA positively supercoiled this

41
Q

Ciproflaxin

A

An antibiotic that prevents the resealing of strand breaks, broad spectrum

42
Q

What do antibiotics due?

A

Inhibit DNA gyrase and topoisomerase IV

43
Q

Which moves faster through gel, relaxed or supercoiled DNA?

A

Supercoiled

44
Q

What would a superhelical density of -0.03 indicate?

A

3% of the helical turns present in the DNA have been removed. The negative sign indicates that the change is due to underwinding

45
Q

Why are topoisomerases a target of chemotherapy?

A

Tumor cells generally contain elevated levels of topoisomerases

-healthy cells can also be affected

46
Q

SMC proteins

A

Structural maintenance of chromosomes

  • promote chromosome condensation by creating physical contact between segments of DNA that are not in close proximity
  • found in all organisms
  • occur during mitosis and DNA repair
  • cohesion: forms loops between sister chromatids
  • condensin: interacts with the DNA and causes the DNA to become more condense
  • separase: cuts proteins
47
Q

Coding information:

A

Proteins and functional RNAs

48
Q

Sequence information:

A
  • replication start and stop
  • protein attachment
  • chromosome maintenance

Molecular Biology (4 decks)

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