Nucleus

Question 1

Function of the nucleus

Answer 1

1- Controls all the function of the cell
2- storing of the genetic material
3- determine the type and the function of the cell
4- formation if RNA
5- play an important role in heredity

Question 2

Staining of the nucleus

Answer 2

Has basophilic structure it can be stained by hematoxylin its color is blue .

Question 3

Nucleus position

Answer 3

Central , peripheral , basal , eccentric

Question 4

Size of nucleus

Answer 4

Small , medium , large ,

“ its very in size “

Question 5

Shape of nucleus

Answer 5

Rounded , oval , flattened , elongated , rod shaped , bilobed , kidney shaped , segmented
“ vary in shape “

Question 6

Number of nucleus

Answer 6

• Usually there is one nucleus in each cell
• tow nucleus may be present in liver cells or transitional epithelium
• more then two nucleus are present in osteoblasts cells of bone or skeletal muscle cells

Question 7

Location of nucleus

Answer 7

Present in all mammalian cells except red blood corpuscles

Question 8

Structure of nucleus from outside to inside

Answer 8

• nuclear membrane / envelope
• nuclear sap / karyolymph
• nucleolus
• chromatin — euchromatin — heterochromatin

Question 9

What is the nuclear membrane

Answer 9

• It is a membrane that surround the nucleus

- this membrane disappear during cell division

Question 10

Nuclear membrane under L.M.

Answer 10

Appear as basophilic single line .

Question 11

Nuclear membrane under E.M.

Answer 11

• Two thin membranes separated by a perinuclear space
• inner nuclear membrane
• outer nuclear membrane
• nuclear pores

Question 12

Inner nuclear membrane contains ?

Answer 12

It has a chromatin granules on the inner space

Question 13

Outer nuclear membrane contains ?

Answer 13

It has ribosomes on the outer surface

Question 14

What is the nuclear pore ?

Answer 14

It is a canal between inner and outer membrane in order to form diaphragm

Question 15

Function of diaphragm

Answer 15

• regulate the exchange process of metabolites and molecules between nucleus and cytoplasm
• regulate the passage of RNA from inside to outside the nucleus

Question 16

Definition of chromatin

Answer 16

Are particles and thread which form the chromosomes during cell division

Question 17

Structure of chromatin

Answer 17

It is composed of DNA and Histone

Question 18

Chromatin under L.M.

Answer 18

Appear as coarse and fine basophilic granules

Question 19

Types of chromatin

Answer 19

1- Euchromatin / extended chromatin / active chromatin

2- heterochromatin / condensed chromatin / inactive chromatin

Question 20

Function of chromatin

Answer 20

1- guide the protein synthesis inside the cell
2- stores the genetic information
— which are transmitted through successive generation
— this done through duplication of DNA
— before the starting of cell division
3- m RNA , t RNA , r RNA , are synthesized from DNA which located in chromatin .

Question 21

Structure of DNA “ deoxy ribonucleic acid “

Answer 21

• Has a double helix chain
• each chain is formed of phosphate and sugar ( deoxyribose ) groups
• the double helix chain are linked transversally by a base ( nitrogenous base )
• this base extend laterally from each sugar group

Question 22

There is four types of nitrogenous bases in the DNA molecule which are ?

Answer 22

1- adenine (A)
2- thymine (T)
3- guanine (G)
4- cytosine (C)

Question 23

Function of DNA

Answer 23

The main function of DNA is the transferring of “genes” ( genetic information ) by two processes .
1- replication of DNA , which form more DNA
2- transcription of DNA , which form three types of RNA , rRNA , tRNA , mRNA .

Question 24

Location of DNA

Answer 24

Present in nucleus and mitochondria

Question 25

Staining of DNA

Answer 25

DNA takes blue color with methyl-green pyronin stain

Question 26

Structure of RNA

Answer 26

- each RNA is formed of single stand of helix , however some RNAs have double helix . - each RNA stand contain ribose sugar instead of deoxyribose sugar

Question 27

Location of RNA

Answer 27

Present in nucleus and cytoplasm

Question 28

Staining of RNA

Answer 28

With methyl - green pyronin RNA takes red color .

Question 29

Formation of ribosomal RNA

Answer 29

Formed in nucleus from a loop of DNA called nuclear organizer

Question 30

The pathway of Ribosomal RNA

Answer 30

The newly formed ribosomal RNA molecules are transported to the cytoplasm

Question 31

The Function of ribosomal RNA

Answer 31

They serve as essential sites for protein synthesis ( factories of protein formation )

Question 32

Formation of messenger RNA

Answer 32

The information codes for protein synthesis are present on the DNA molecule as a series of units , from this DNA molecule , messenger RNA is formed carrying the information codes of protein synthesis .

Question 33

The pathway of Messenger RNA

Answer 33

The newly formed messenger RNA is then transported to the cytoplasm carrying with it the information which controls the process of protein synthesis at the sites of cytoplasmic ribosomes

Question 34

Formation of transfer RNA

Answer 34

The formation of t RNA occurs inside the nucleus from a special type of DNA molecule

Question 35

The pathway of t RNA

Answer 35

To the cytoplasm

Question 36

Function of t RNA

Answer 36

- they play an important role in the process of protein synthesis - there are a different forms of t RNA which transfer specific amino acids from the cytoplasm to their specific position in polypeptide chains - the amino acids in this process are have been activated by special enzymes - the polypeptide chains are manufactured in the ribosomal RNA

Question 37

Nucleolus under L.M

Answer 37

appears as a dark basophilic mass

Question 38

Nucleolus under E.M

Answer 38

Formed of an irregular spongy mass not limited by a membrane , it shows light and dark areas .

Question 39

Function of nucleolus

Answer 39

- It forms r RNA which pass through the nuclear pores to the cytoplasm , - the r RNA considered as factories for protein synthesis

Question 40

Structure of nucleolus

Answer 40

It is formed mainly of protein , RNA and DNA , also contains certain enzymes as acid phosphatase and RNA methylase .

Question 41

Appearance of nucleolus

Answer 41

Disappears during cell division , reappears in the new daughter cells

Question 42

Nucleolus staining

Answer 42

It is basophilic because it is rich in RNA

Question 43

Shape of nucleolus

Answer 43

It is rounded in shape surrounded by chromatin material .