Lecture 10: Nucleus

Question 1

Nucleus:

Answer 1

5-10 micrometers
one per cell
cells control centre
contains cells genes

Question 2

Nuclear envelope:

Answer 2

two membranes

both phospholipid bilayers

Question 3

Nuclear pore complex:

Answer 3

controls movement of molecules in/out of the nucleus

Question 4

Out of nuclear pore complex:

Answer 4

mRNA - carrier information from a gene

tRNA/ribosomal subunits - needed to build proteins

Question 5

in nuclear pore complex:

Answer 5

control signals
building materials for RNA
energy for chemical synthesis

Question 6

Within the nucleus:

Answer 6

nuclear envelope lined by the nuclear lamina

Question 7

nuclear lamina

Answer 7

made of intermediate filaments

maintains cell structure/organise packing of DNA

Question 8

The nucleolus:

Answer 8

• prominent nuclear structure
• may be 2+ nucleoli per cell
• nucleolus responsible for making ribosomal RNA

Question 9

DNA organisation within the nucleus:

Answer 9

a DNA double helix forms that’s about 2nm in diameter

Question 10

from a 2nm double helix…

Answer 10

it interacts with specific proteins called histones (H2-H4) forming a 10nm fibre ‘bead’ called a nucleosome

Question 11

following nucleosomes…

Answer 11

the DNA interacts with another histone (H1) forming a 30nm fibre

Question 12

30nm DNA fibre…

Answer 12

loops to form 300nm a 300nm fibre

Question 13

During cell devision the 300nm fibres…

Answer 13

coil to form metaphase chromosomes

Question 14

Euchromatin:

Answer 14

• less dense

- contains genes being used by the cell

Question 15

Heterochromatin:

Answer 15

• more dense

- contains genes not being used by the cell