Lecture 3: Nucleus and chromatin structure

Question 1

_____________ houses the genetic material encoded in the DNA of the chromatin and directs protein synthesis in the cytoplasm via rRNA, mRNA, tRNA. It is the largest organelle of the cell.

Answer 1

Nucleus

Question 2

What is the only eukaryotic cells that do not contain nucleus

Answer 2

erythrocyte

Question 3

The nuclear envelope is _____________ that encloses the nucleus during a cells life cycle

Answer 3

nuclear envelope
contrains an inner and outer membrane

Question 4

What are the inner and outer membranes of the nuclear envelope separated by

Answer 4

perinuclear cisterna

Question 5

What is in the outer nuclear membrane

Answer 5

numerous ribosomes

Question 6

What is in the inner nuclear membrane

Answer 6

-covered by the nuclear lamina, a network of intermediate filaments (lamins) that stabilizes the membrane
-Nuclear lamins provide mechanical support and are involved in various processes of the cell cycle (e.g., transcription, signal transduction, chromatin organization)

Question 7

A mutation in the gene encoding for lamin A results in

Answer 7

Hutchinson-Gilford progeria syndrome

Question 8

Genetic condition characterized by the dramatic, rapid appearance of aging beginning in childhood.
* Affected children typically look normal at birth and in early infancy, but then grow more slowly than other children and do not gain weight at the expected rate (failure to thrive).
* They develop a characteristic facial appearance including prominent eyes, a thin nose with a beaked tip, thin lips, a small chin, and protruding ears.
* The LMNA gene provides instructions for making a protein called lamin A.
* This protein plays an important role in determining the shape of the nucleus within cells.
* It is an essential scaffolding (supporting)

Answer 8

Hutchinson- Gilder Progeria syndrome

Question 9

What gene is involved in Hutchinson- Gilder Progeria syndrome

Answer 9

The LMNA gene provides instructions for making a protein called lamin A.

Question 10

The nuclear envelope in perforated with holes called _____________

What is their function?

Answer 10

Nuclear pores
-regulate the passage of molecules between the nucleus and cytoplasm: permitting some to pass through the membrane but not others. (Molecules allowed got pass are RNA, DNA, and molecules required for genetic material)

Question 11

________________ is composed of nearly 100 proteins some of which are arranged in eightfold symmetry around the margin of the pore. It permits the passive movement across the nuclear envoled via open channels for simple diffusion. Most proteins regardless of size pass in either direction only by receptor mediated transport.

Answer 11

Nuclear pore complex

Question 12

__________ dense non membrane bound structure. Some cells have more than one.

What does is do?

Answer 12

Nucleolus

-Contains rDNA –> transcribed into rRNA
-assembles ribosomal subunits

Question 13

The human genome is contains in what two compartments of the cell

Answer 13

Nucleus and mitochondria

Question 14

The bulk of the genome is within _________________

Answer 14

a set of linear chromosomes within the cell nucleus and contains genetic material of both material and paternal DNA

Question 15

What are the the components of DNA

Answer 15

-Base (purine or pyrimidine)
-Deoxyribose sugar
-phospate group

Question 16

What is a purine

Answer 16

heterocyclic compounds
Adenine and Guanine

Question 17

What is a pyrimidine

Answer 17

two side membered rings. Cytosine, uracil, and thymidine

Question 18

the hydrophilic ______________________ back bone of the double helix is on the outside whereas the hydrophobic bases are stacked inside

Answer 18

deoxyribose phosphate

Question 19

_________ and ___________ are located between the grooves of the DNA

Answer 19

major and minor grooves

*grooves provide access for the binding of regulatory proteins to their specific recognition sequence along the DNA chain

Question 20

What tow things stabilize the interactions between the stacked bases of DNA

Answer 20

1. hydrogen bonds of base pairs
2. hydrophobic interactions between the stacked bases

Question 21

Why is more energy required to break the bond between GC than AT

Answer 21

There are 3 hydrogen bonds as apposed to 2. This plays an important role in the thermodynamics of DNA

Question 22

__________ form of DNA is the Dnal form

Answer 22

B-Form

Question 23

What does chromatin consist of

Answer 23

1. very long double stranded DNA molecules
2. equal mass of small basic proteins: histones
3. Smal quantities of ribonucleic acid RNA

Question 24

What are histones

Answer 24

heterogeneous group of closely related arginine- and
lysine-rich basic proteins, which together make up one-
fourth of amino acid residues.

*they allow for the compaction of chromatin

Question 25

___________ are the functional organization upon which the higher order packing of chromatin is built.

Answer 25

Nucleosome

Question 26

Nucleosome core consists of complex of ____________________

Answer 26

eight histone proteins (two molecules each of histones with double stranded DNA wound around it)

Question 27

________________ of DNA are associated with the nucleosome particle and 50 to 70 bp span of linker DNA bound by linker histone H1 operates each nucleosome

Answer 27

146 base pairs BP

Question 28

minor histone variants exits in the eukaryotic genome _____________ is sometimes present in the place of H2A and is known to participate in the chromosome repair process

Answer 28

H2AX

Question 29

_______________ also regulates gene expression or activity by determine whether the DNA sequence can be accessed by transcription factors

Answer 29

Nucleosome

Question 30

________________ of histone changes its physical properties including altering its affinity for DNA

Answer 30

covalent modification

Question 31

________________ generally leads to reduced affinity for DNA and loosens packing

-increased transcription (of specific genes)

Answer 31

acetylation of the histone

Question 32

_____________ leads to increased affinity for DNA and tighter packing decree transcription of specific genes

Answer 32

Methylation of histones

Question 33

Where are histones modified

Answer 33

chromatin remodeling complexes

Question 34

What are 5 properties of Euchromatin

Answer 34

Extended chromatin
* Less condensed
* Formed by adjacent nucleosomes
where the nucleosome core
consisted of two copies each of
histones H2A, H2B, H3 and H54.
* Gene-rich
* Easily transcribed

Question 35

What are five properties of heterochromatin

Answer 35

Highly condensed
* Contains an additional histone, H1,
which wraps around groups of
nucleosomes, thus forming 30nm
diameter filaments of helical coils
of six nucleosomes per turn
* Gene-poor
* Transcriptionally silen

Question 36

_______ consists of chromatin extensively folded in loops that maintain by DNA binding proteins, single long DNA molecular histones that are assembles in nucleosomes.

Answer 36

chromosome

Question 37

Which part of the nucleus assembles the ribosomal subunits

Answer 37

nucleolus

Question 38

What are the three parts of the nucleotide

Answer 38

-base
-deoxyribose sugar
-phosphate group

Question 39

What are the function of the nuclear laming and what disorder is caused by a mutation in them

Answer 39

Nuclear lamina acts in mechanical support for the cell membrane and are involved in various process o the cell cycle

leads to hutchinson Gilford progeria syndrome