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Intro To Biochem: DNA-Msap Wk 1 > DNA Packing > Flashcards

DNA Packing Flashcards

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1
Q

What is the primary protein that complex DNA in eukaryotes?

A

Histones

Histones are proteins that help package DNA into a more compact structure.

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2
Q

What is the term used to describe the highly dense structures formed by DNA and histones?

A

Quaternary Structure

This term refers to the complex assembly of proteins and nucleic acids.

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3
Q

What is the length of chromosomal DNA in eukaryotes?

A

Just under 0.05m

This length is significantly reduced when compacted into chromosomes.

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4
Q

What is the typical length range of chromosomes in eukaryotes?

A

1 to 10µm

Chromosomes are much shorter than the total length of chromosomal DNA.

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5
Q

List the levels of packaging for eukaryotic DNA.

A
  • Nucleosomes
  • Loops of fibers (beads-on-a-string)
  • 30mm fibers

These levels represent the hierarchical organization of DNA.

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6
Q

Fill in the blank: Eukaryotic DNA is complexed to _______ to form a highly dense structure.

A

Histones

This complex formation is essential for DNA packaging.

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7
Q

What is the basic unit of Eukaryotic chromosome structure?

A

Nucleosome

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8
Q

What proteins make up the histone core of a nucleosome?

A

Four pairs of protein monomers: H2A, H2B, H3, and H4.

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9
Q

What is the composition of the nucleosome core particle?

A

A histone octamer and about 146 base pairs of DNA.

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10
Q

What is the diameter of a nucleosome?

A

5.7 nm

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11
Q

What additional component does each nucleosome contain?

A

Histone H1 and linker DNA.

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12
Q

How long is the linker DNA in a nucleosome?

A

About 54 base pairs.

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13
Q

What role does Histone H1 play in the nucleosome?

A

It binds to the core particle and to linker DNA.

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14
Q

What is the diameter of the nucleosome structure?

A

11 nm

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15
Q

What does ‘beads-on-a-string’ packaging of DNA represent?

A

It represents the 1st level of chromosomal packing.

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16
Q

What is the ‘beads-on-a-string’ form of chromatin composed of?

A

Beads = core nucleosome (11 nm)

String = DNA

17
Q

How are nucleosomes connected together?

A

Nucleosomes are connected together by linker DNA and histone (H1).

18
Q

What is the diameter of the resulting chromatin fiber?

A

The resulting fiber is about 30nm in diameter.

19
Q

How do nucleosomes associate with each other?

A

Nucleosomes can associate with each other through interactions between histone H1 to form a more compact structure (chromatin fiber).

20
Q

What is the effect of 30nm fiber packaging on DNA?

A

It makes DNA even more condensed.

21
Q

How is the chromatin fiber structured?

A

Packed on top of one another, generating a regular array.

22
Q

What is the diameter of the resulting chromatin fiber?

A

The resulting fiber is about 30nm in diameter.

23
Q

How do nucleosomes associate with each other?

A

Nucleosomes can associate with each other through interactions between histone H1 to form a more compact structure (chromatin fiber).

24
Q

What is the effect of 30nm fiber packaging on DNA?

A

It makes DNA even more condensed.

25
Q

How is the chromatin fiber structured?

A

Packed on top of one another, generating a regular array.

26
Q

What type of DNA do prokaryotes have?

A

Prokaryotic DNA is circular and double-stranded.

27
Q

What happens to the double helix during prokaryotic DNA packaging?

A

A few turns of the double helix are removed.

28
Q

What is formed when prokaryotic DNA is supercoiled?

A

The molecule forms a negative supercoil.

29
Q

How do prokaryotes compress their DNA?

A

Prokaryotes compress their DNA into smaller spaces by supercoiling.

30
Q

What is the role of multiple proteins in prokaryotic DNA packaging?

A

Multiple proteins act together to fold and condense prokaryotic DNA.

31
Q

What are HU proteins?

A

HU proteins are a type of protein involved in prokaryotic DNA packaging.

32
Q

How do HU proteins interact with DNA in E. coli?

A

HU proteins in E. coli form a tetramer wound with about 60bp of DNA.

33
Q

How many HU proteins are present in an E. coli cell?

A

There are about 60,000 HU proteins per E. coli cell.

34
Q

What is the structure of E. coli nucleoid?

A

E. coli nucleoid model shows DNA packed in a protein core by HU proteins.

Intro To Biochem: DNA-Msap Wk 1 (4 decks)

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