bio AS ..doubt !!:(

[Assi1993]

heyy, i cant understand the difference between chromatic and nucleolus??
can some1 explain plzz..would b very thankful !!

[MaNi_DaDuDe]

heyy, i cant understand the difference between chromatic and nucleolus??
can some1 explain plzz..would b very thankful !!

What? You mean Chromatin ? orrr 

If that's the case, I can easily tell you the difference by showing you a picture or two. Let me know.

Chromatin

(a)                    Chromatin is a complex of DNA and protein

(b)                    Chromatin is not visible, as individual chromosomal entities, through a light microscope

(c)                    Prior to cell division (M phase) a eukaryotic cell's genome consists of chromatin

Nucleus

(a)                    In eukaryotic cells the cell DNA is separated from the cytoplasm

(b)                    Most of this DNA is contained within the cell's nucleus

(c)                    The DNA within the nucleus is found as DNA-protein structures called chromatin

(d)                    During cell division, nuclear DNA is organized into chromosomes

(e)                    The structure that serves to divide the interior of the nucleus from the cytoplasm is the nuclear membrane

(f)                      Prokaryotic cells, by definition, lack nuclei (which is the plural of nucleus)

heyy, i cant understand the difference between chromatic and nucleolus??
can some1 explain plzz..would b very thankful !!

What? You mean Chromatin ? orrr 

If that's the case, I can easily tell you the difference by showing you a picture or two. Let me know.

Chromatin

(a)                    Chromatin is a complex of DNA and protein

(b)                    Chromatin is not visible, as individual chromosomal entities, through a light microscope

(c)                    Prior to cell division (M phase) a eukaryotic cell's genome consists of chromatin

Nucleus

(a)                    In eukaryotic cells the cell DNA is separated from the cytoplasm

(b)                    Most of this DNA is contained within the cell's nucleus

(c)                    The DNA within the nucleus is found as DNA-protein structures called chromatin

(d)                    During cell division, nuclear DNA is organized into chromosomes

(e)                    The structure that serves to divide the interior of the nucleus from the cytoplasm is the nuclear membrane

(f)                      Prokaryotic cells, by definition, lack nuclei (which is the plural of nucleus)


--Maybe Irrelevant--
If you are studying nuclear division. . have a look at :



Interphase is stage I of the diagram


    * Prophase, Stage II,III- The chromatin condenses into a highly ordered structure called chromosomes and the nuclear membrane begins to breakup. The nucleus also breaks up and forms part of several chromosomes. Centrioles move to opposite poles of nucleus.


    * Metaphase, Stage IV - Condensed chromosomes, carrying genetic information, align in the middle of the cell before being separated into each of the two daughter cells.


    * Anaphase - Stage V, VI Chromatids (identical copies of chromosomes) separate as they are pulled towards opposite poles within the cell. They are pulled because the microtubule fibres begin to shorten, pulling them along.


    * Telophase - Nucleus, nucleolus reforms and chromosomes unravel into longer chromatin structures for reentry into interphase. Cytokinesis also occurs - the division of cytoplasm and cell into two by constriction from edges of cell.


This section is called the PMAT section as it is an easy way to remember the stages of mitosis (Prophase-Metaphase-Anaphase-Telophase).

Hope I helped.


-MaNi

P.S. Asmaa? lol

[MaNi_DaDuDe]

Googled something for ya:

In eukaryotic cells, the structure and contents of the nucleus are of fundamental importance to an understanding of cell reproduction. The nucleus contains the hereditary material of the cell assembled into chromosomes. In addition, the nucleus usually contains one or more prominent nucleoli (dense bodies that are the site of ribosome synthesis).

The nucleus is surrounded by a nuclear envelope consisting of a double membrane that is continuous with the endoplasmic reticulum. Transport of molecules between the nucleus and cytoplasm is accomplished through a series of nuclear pores lined with proteins that facilitate the passage of molecules out of and into the nucleus. The proteins provide a certain measure of selectivity in the passage of molecules across the nuclear membrane.

The nuclear material consists of deoxyribonucleic acid (DNA) organized into long strands. The strands of DNA are composed of nucleotides bonded to one another by covalent bonds. DNA molecules are extremely long relative to the cell; indeed, the length of a chromosome may be hundreds of times the diameter of its cell. However, in the chromosome, the DNA is condensed and packaged with protein into manageable bodies. The mass of DNA material and its associated protein is chromatin.

To form chromatin, the DNA molecule is wound around globules of a protein called histone. The units formed in this way are nucleosomes. Millions of nucleosomes are connected by short stretches of histone protein much like beads on a string. The configuration of the nucleosomes in a coil causes additional coiling of the DNA and the eventual formation of the chromosome.

[Assi1993]

lol ya sorry *Chromatin*!!
well maanii!!! thank you so much for ur consideration but i got the answer..as simple,,

Chromatin is DNA in its active form. It consists of DNA looped around histone proteins. The nucleolus is a knot of chromatin and manufactures ribosomes....

[MaNi_DaDuDe]

lol ya sorry *Chromatin*!!
well maanii!!! thank you so much for ur consideration but i got the answer..as simple,,

Chromatin is DNA in its active form. It consists of DNA looped around histone proteins. The nucleolus is a knot of chromatin and manufactures ribosomes....

yeah no problemo.

Take care now

[Metallicnak]

Hey guys, i was just going through my cell division notes and came across this doubt that annoys me preety much:

During the interphase of Mieosis the the DNA which is in the form of chromatin replicates and by Prophase 1 the chromatin condense forming chromasomes. Each chromasome then pairs up to its identical to form a Homalogous pair right?  So does homologous chromasomes form during the prophase of Mitosis as well Oh and the other thing is that when homolougous chromasomes are formed are the chromasomes whithin the pair exactly identical to each other

Much help would be appreciated

[nid404]

I'll try my best to explain...
It's highly complex genetics...but i like it 

In most eukaryotic cells, there are two sets of chromosomes.
The presence of two sets is a consequence of sexual
reproduction; one set is inherited from the male parent
and the other from the female parent. Each chromosome in
one set has a corresponding chromosome in the other set,
together constituting a homologous pair..
The two chromosomes of a homologous pair are usually
alike in structure and size, and each carries genetic
information for the same set of hereditary characteristics.
(An exception is the sex chromosomes)

For example, if a gene on a particular
chromosome encodes a characteristic such as hair color,
another gene (called an allele) at the same position on that
chromosome’s homolog also encodes hair color. However,
these two alleles need not be identical: one might produce
red hair and the other might produce blond hair. Thus,
most cells carry two sets of genetic information; these cells
are diploid. But not all eukaryotic cells are diploid: reproductive
cells (such as eggs, sperm, and spores) and even
nonreproductive cells in some organisms may contain a single
set of chromosomes. Cells with a single set of chromosomes
are haploid.Haploid cells have only one copy of each
gene.

[Metallicnak]

Thanks Nid tht cleared up preety much about the homologous chromasomes  , but does homologous pair form during the prophase of mitosis... like in Prophase 1 of mieosis

[MaNi_DaDuDe]

Thanks Nid tht cleared up preety much about the homologous chromasomes  , but does homologous pair form during the prophase of mitosis... like in Prophase 1 of mieosis

no. Mitosis has no homologous pairing.. no bivalents..

If you still don't understand, check : http://www.le.ac.uk/ge/genie/vgec/he/cellcycle.html

[Metallicnak]

Thanks fr the info mani By the way do u also happen to know any other usefull sites for Bio like this 1 maybe with animations and all would be really helpfull while studying.

[3ishakay]

heyy ..
iv got a question ..
pls any1 anser ir supa detail =D

explain the
differences between blood, tissue fluid and lymph ..

n meiosis aint rlly in AS is it?? :S

[Saladin]

The definitions of Plasma, tissue-fluid and lymph are as under. The difference can be understood from these definitions.

Blood plasma is the liquid component of blood, in which the blood cells are suspended. Plasma is the largest single component of blood, making up about 55% of total blood volume. Serum refers to blood plasma in which clotting factors (such as fibrin) have been removed. Blood plasma contains many vital proteins including fibrinogen, globulins and human serum albumin.

Interstitial fluid (or tissue fluid, or intercellular fluid) is a solution which bathes and surrounds the cells of multicellular animals.
It is one of the two components of extracellular fluid, the other being plasma.
On average, a person has about 11 litres (2.42 gallons) of interstitial fluid providing the cells of the body with nutrients and a means of waste removal.

The lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, and lymph vessels that produce and transport lymph fluid from tissues to the circulatory system. The lymphatic system is a major component of the immune system.
The lymphatic system has three interrelated functions: (1) removal of excess fluids from body tissues, (2) absorption of fatty acids and subsequent transport of fat, chyle, to the circulatory system and, (3) production of immune cells (such as lymphocytes, monocytes, and antibody producing cells called plasma cells).

[3ishakay]

The definitions of Plasma, tissue-fluid and lymph are as under. The difference can be understood from these definitions.

Blood plasma is the liquid component of blood, in which the blood cells are suspended. Plasma is the largest single component of blood, making up about 55% of total blood volume. Serum refers to blood plasma in which clotting factors (such as fibrin) have been removed. Blood plasma contains many vital proteins including fibrinogen, globulins and human serum albumin.

Interstitial fluid (or tissue fluid, or intercellular fluid) is a solution which bathes and surrounds the cells of multicellular animals.
It is one of the two components of extracellular fluid, the other being plasma.
On average, a person has about 11 litres (2.42 gallons) of interstitial fluid providing the cells of the body with nutrients and a means of waste removal.

The lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, and lymph vessels that produce and transport lymph fluid from tissues to the circulatory system. The lymphatic system is a major component of the immune system.
The lymphatic system has three interrelated functions: (1) removal of excess fluids from body tissues, (2) absorption of fatty acids and subsequent transport of fat, chyle, to the circulatory system and, (3) production of immune cells (such as lymphocytes, monocytes, and antibody producing cells called plasma cells).

10xx :D

hey wd u also xplain the exterior and interior structure of the heart?

i didnt evn open the book until today and i dnt get it .. :S

[nid404]

http://www.biologymad.com/

[MaNi_DaDuDe]

Thanks fr the info mani By the way do u also happen to know any other usefull sites for Bio like this 1 maybe with animations and all would be really helpfull while studying.

@3ishakay - Meisois isn't in AS.

Amazing links at https://studentforums.biz/index.php/topic,5002.0.html for Biology.