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* CELS191 > Lecture 11: How Are Cellular Events Controlled? > Flashcards

Lecture 11: How Are Cellular Events Controlled? Flashcards

1
Q

What is the most prominent organelle and how big is it?

A

The nucleus, 5-10μm in diameter.

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2
Q

Does the nucleus hold all of the cell’s genes?

A

Most, but not all.

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3
Q

What is the function of the nucleus?

A

Serves as repository of genetic information and the cell’s control centre.

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4
Q

What surrounds the nucleus?

A

The nuclear envelope.

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5
Q

Describe the nuclear envelope. (2)

A

Composed of two membranes, each a phospholipid bilayer. Inner surface is lined by the nuclear lamina.

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6
Q

What is the nuclear lamina made of?

A

Intermediate filaments.

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7
Q

What is the function of the nuclear lamina?

A

• helps maintain shape
of nucleus
• and organise the
packing of the DNA

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8
Q

What happens if nuclear lamina is defective?

A

Hutchinson-Gilford Progeria syndrome

cell nuclei have abnormal shape, results in accelerated aging

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9
Q

What is the purpose of nuclear pores? (3)

A
  • mRNA, rRNA and tRNA out of nucleus
  • control signals move into nucleus
  • energy and materials into nucleus
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10
Q

What type of polymer is DNA?

A

A nucleotide polymer.

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11
Q

How much DNA does each human cell contain?

A

about 2.5m (250,000x diameter of nucleus)

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12
Q

DNA must be very well _____ but also _________.

A

DNA must be very well PACKED but also ACCESSIBLE.

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13
Q

How are chromatin fibres formed?

A

DNA double helix combined with histone proteins.

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14
Q

Chromatin fibres undergo _____-______ _______

A

Chromatin fibres undergo multi-level packaging

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15
Q

What is the diameter of a DNA double helix?

A

About 2nm

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16
Q

What is the diameter of a chromatin

A

About 10nm

17
Q

What is a nucleosome?

A

A length of DNA coiled around a core of histones (a bead) (multiple nucleosomes form a chromatin).

18
Q

How does a 10nm chromatin fibre form a 300nm fibre?

A

Chromatin fibres further interact with another histone (H1) and cause to 10nm fibre to coil and form a 30nm fibre. The 30nm fibre loops to form a 300nm fibre.

19
Q

What happens to the 300nm fibres during metaphase?

A

During cell division the 300nm fibres coil to

form metaphase chromosomes.

20
Q

What is euchromatin?

A

A less dense, genetically active (often) region of chromatin during interphase.

21
Q

What is heterochromatin?

A

A dense, genetically inactive region of chromatin during interphase.

22
Q

Is the location of a chromosome within a nucleus random?

A

No.

* CELS191 (12 decks)

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