Nucleus

Question 1

What are the 5 basic/ key details about the nucleus?

Answer 1

• The most prominent organelle ( 5-10μm)
• One nucleus per cell ( mostly)
• Contains most of cells genes
• Serves as a repository of inherited genetic information
• Acts as cells control centre

Question 2

How many membranes does the nucleus have?

Answer 2

2

Question 3

What is the role of the nuclear pore complex?

Answer 3

Controls movement of molecules into and out of the nucleus

Question 4

What does the nuclear pore complex allow out of the nucleus? (3)

Answer 4

• mRNA
• tRNA
• ribosomal subunits

Question 5

What does the nuclear pore complex allow into the nucleus?

Answer 5

• control signals
• building materials
• ATP

Question 6

What is inner surface of nuclear envelope lined by?

Answer 6

Nuclear Lamina

Question 7

What is the nuclear laminar composed of?

Answer 7

intermediate filaments

Question 8

What is the role of the nuclear lamina?

Answer 8

• maintains shape of nucleus

- helps organise the packing of DNA within nucleus

Question 9

What. does a defective nuclear lamina result in?

Answer 9

• occurs in some genetic disorders that produce a defective lamin protein
• nuclei cannot maintain a spherical shape
• limits ability of affected cells to divide
• results is abnormal features and premature aging

Question 10

What is the nucleolus? What is it responsible for?

Answer 10

• A prominent nuclear structure within non dividing cells

- responsible for making ribosomal RNA which combines with proteins to produce ribsosomes

Question 11

What length of DNA does each human cell contain?

Answer 11

approx. 2.5m

Question 12

How does the DNA double helix (2nm diameter) become a 10nm diameter fibre?

Answer 12

• through interaction with proteins called histones (H2-H4)
• 8 Histones make an octamer for DNA to wrap around
• this creates “beads” called nucleosomes
• Results in a 10nm fibre

Question 13

What does interaction with the Histone (H1) protein cause in a DNA fibre? What continues to happen to complete the organization of DNA within a nucleus

Answer 13

• coils to form a 30nm fibre
• 30nm fibre loops to make 300nm fibre
• During cell division the 300nm fibre coils to form metaphase chromosomes

Question 14

What are the 2 forms of Non metaphase organizations of chromatin?

Answer 14

• euchromatin

- heterochromatin

Question 15

What is chromatin?

Answer 15

The material of which DNA chromosomes are composed of- protein, RNA, and DNA

Question 16

What is Euchromatin?

Answer 16

Less dense organization of chromatin and contains genes actively being used by that cell for easier access

Question 17

What is Heterochromatin?

Answer 17

Denser organization of chromatin containing genes not actively being used by that cell