the Nucleus

Question 1

describe the nucleus

Answer 1

• the most important organelle (5-10 micrometers)
• one nucleus per cell
• contains most of the cells genes
• perinucleus space
• the nucleus envelope is continuous to the ER
• the perinucleus space is continuous to the lumen ER
• serves as repository inherited genetic information
• has 2 membranes

Question 2

describe the nucleus pore complex

Answer 2

• Controls the movement of molecules out of or into the nucleus

Question 3

what goes out of the nucleus pore complex

Answer 3

• mRNA: messenger RNA - carries information from a gene

- tRNA: transfer RNA , and Ribosomes are needed to build proteins

Question 4

what goes into the nucleus pore complex

Answer 4

• control signals: to tell when to turn a gene on or off
• building blocks: to build RNA
• energy: for chemical synthesis

Question 5

within the nucleus, what is the inner surface of the nuclear envelope lined with

Answer 5

• nuclear lamina

Question 6

what is the nuclear lamina composed of

Answer 6

• intermediate filaments

Question 7

what does the nuclear lamina do

Answer 7

• helps maintain shape of nucleus

- helps to organize the packing f the DNA within the nucleus

Question 8

what is the Nucleolus

Answer 8

• a prominent nuclear structure within non-dividing cells

- may be 2 or more nucleoli per cell depending on species and stage of cell cycle

Question 9

what is the nucleolus responsible for

Answer 9

• for making ribosomal RNA which then combines with proteins to produce ribosomes

Question 10

how big is the DNA double helix

Answer 10

2nm in diameter

Question 11

what does the helix interacts with

Answer 11

• histones (H2-H4)

Question 12

what does the interaction between the helix and histones form

Answer 12

it forms a 10nm diameter fiber called nucleosome

Question 13

another interaction occurs between DNA and another Histone (H1), what does this do

Answer 13

• causes the 10nm coil to form a 30nm fiber

Question 14

what does the 30nm fiber then do

Answer 14

loops to form a 300nm fiber

Question 15

during cell division what does the 300nm fiber coil form

Answer 15

metaphase chromosomes

Question 16

what is euchromatin

Answer 16

• they are less dense, and contains genes that are being used by that cell

Question 17

what is heterochromatin

Answer 17

• are more dense, and contains genes that are not being used by that cell