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Bio 233 > DNA Organization > Flashcards

DNA Organization Flashcards

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1
Q
  • Circular chromosomes
  • Double stranded (dsDNA)
  • May also contain plasmids
  • Found in the nucleoid
A

Organization of DNA in most prokaryotes

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2
Q

Back bone has been nicked.

-relaxes from supercoiling

A

Relaxed circular DNA

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3
Q

Allows DNA to fit inside the cell

-Amount and type of supercoiling depends on the starting point

A

Supercoiled Circular DNA

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4
Q

Formation from contortion of supercoiling and twisting.

A

2 supercoiled DNA forms

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5
Q

Untwisting the DNA

-Compacting DNA

A

Negative supercoiling

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6
Q

Twisting

  • introducing more twisting causes DNA to contort.
  • Compacting DNA
A

Positive supercoiling

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7
Q 
Amount and type of supercoiling controlled by:?
-highly conserved enzymes
-relieve twisting by two types:
 I. Make a nick in one strand
 II. Cuts both strands
A

Topoisomerases

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8
Q

2 DNA linked like a chain

A

Catenated DNA

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9
Q

How doe bacteria package their DNA?

a. using histones
b. by supercoiling the DNA
c. by acetylating the DNA
d. by methylating the DNA
e. all of the above

A

b. by supercoiling the DNA

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10
Q

-Nucleus, mitochondria, choloroplasts

A

Organization of DNA in Eukaryotes

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11
Q

Amount of haploid DNA in an organism in base pairs

A

C value

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12
Q

Increase in DNA doesn’t always mean and increase in complexity of the organism.

A

C value paradox

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13
Q

1n

A

haploid

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14
Q

2n

A

diploid

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15
Q

Complete set of chromosomes

A

karyotype

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16
Q

Group that gives DNA its (-) charge

A

Phosphate

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17
Q

DNA is positively or negatively charged?

A

Negatively

18
Q

DNA and associated protein in the nucleus

A

Chromatin

19
Q

Histones

Nonhistones

A

Proteins associated with DNA

20
Q

Help pack chromatin into the nucleus

  • (+) charged because DNA is (-) charged
  • consists of H1, H2A, H2B, H3, H4
  • very highly conserved
A

Histones

21
Q

Various types:

  • DNA replication
  • DNA repair
  • Transcription
  • Recombination
A

Nonhistones

22
Q

DNA wound around a histone core

A

Nucleosomes

23
Q

DNA connecting two nucleosomes together

A

linker DNA

24
Q
  1. Double helix is wound around histones to form nucleosomes
  2. 10nm fiber is condensed and wound into 30 nm fiber
  3. 30nm fiber is attached to protein scaffold.
A

Eukaryotic DNA packing

25
Q

Can unpack and/or repack depending on gene transcription and other events
ex. during the cell cycle

A

Dynamic Packing

Eukaryotic DNA packing

26
Q

Double helix wound around histones to form nucleosomes

A

10 nm fiber

27
Q

Packing is less uniform during interphase (depends on the gene)

  • dynamic upon gene expression
  • organized to support proper gene expression
A

DNA packing

28
Q
  • Chromatin that exhibits normal condensation and decondensation during the cell cycle.
  • genes are actively being transcribed and are thus loosely packed
  • typically devoid of repetitive sequences
A

Euchromatin

29
Q

Two types:

  1. Constitutive Chromatin
  2. Facultative Chromatin
    - Packed tightly
A

Heterochromatin

30
Q
  • Type of heterochromatin
  • present in all cell in the same location on every chromosome
    ex. centromere
A

Constitutive Chromatin

31
Q
  • Type of heterochromatin
  • can change during development
    ex. Barr body on X chromosome
  • DNA condenses or decondenses depending upon the status of the cell. (permanently silencing genes)
  • Euchromatin–>Heterochromatin
A

Facultatvie Chromatin

32
Q

Occurring once or only a few times in the genome

-ex. protein coding

A

Unique-sequence DNA

33
Q

Two types:

  1. Unique-sequence DNA
  2. Repetitive DNA
A

Distribution of sequences

34
Q

Can occur a few times up to a million times, depending on the sequence.
ex. telomeres and rRNA(ribosomal RNA)

A

Repetitive DNA

35
Q

Two types:

  1. Dispersed repeated sequences
  2. Tandemly repeated DNA
A

Repetitive sequence DNA

36
Q

Distributed at irregular intervals on the genome

ex. transposable elements

A

Dispersed Repeated Sequences

37
Q

Sequence that repeats itself many times in a row

ex. telomeres, or genes

A

Tandemly Repeated DNA

38
Q
  • Highly repetitive DNA
  • a fraction of a eukaryotic organism’s DNA that differs in density from most of its DNA as determined by centrifugation, that consists of short repetitive nucleotide sequences, that does not undergo transcription, and that is often found in centromeric regions
A

Satellite DNA

39
Q
  • Consists of heterochromatin
  • tandemly repeated sequences (specifically satellite DNA)
  • form a constrictive region because of tight packing
A

Centromere

40
Q
  • Tandemly repeated DNA at the ends of linear chromosomes.
    ex. TTAGGGTTAGGG…
  • Protect from exonucleases
  • Protect from DNA repair enzymes that form free ended DNA to other free ended DNA
A

Telomeres

41
Q
  • Defense mechanism against foreign DNA

- enzymes that chew up the chromosome

A

exonuclease

Bio 233 (20 decks)

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