Nucleus - Structure and Functions

In the eukaryotic cell, the nucleus is separated from the cytoplasm by a double lipid bilayer membrane known as a nuclear membrane. It encloses the genetic material of a cell. It is also known as karyotheca.

A eukaryotic cell has a nucleus bounded by a double wall membrane structure known as a nuclear membrane. The nuclear membrane has nuclear pore that regulates the exchange of materials between cytoplasm and nucleoplasm. The nucleus contains the chromatin threads and the nucleolus. The gel-like texture of the nucleoplasm embedded with chromatin threads gives it a dense appearance.

A eukaryotic cell has a nucleus, bounded by a double wall membrane structure known as a nuclear membrane. The nuclear membrane is a discontinuous membrane having nuclear pores, which act as a protein channel for regulating the exchange of materials between cytoplasm and nucleoplasm. It regulates the cell in various ways but, the primary function of the nucleus is to contribute in cell division during reproduction by undergoing karyokinesis.
So, the correct answer is option D.

The DNA is the genetic material of the organism which is present in the nucleus. The DNA is bound to the histone proteins and packaged in the nucleus. The DNA contains the segments of genes which encode for the proteins. This genetic information is present in the nucleus of the living cells. 

Cyanobacteria are prokaryotes so, they lack a membrane-bound well-defined nucleus. Cell membrane and ribosomes are the cell structures, common to both prokaryotes and eukaryotes.

DNA is stored in the nucleus, while proteins are assembled from free amino acids in the cytoplasm in structures called ribosomes.

Nucleus and mitochondria are double membrane-bound organelles while ribosome is not membrane bound. Prokaryotes are the organisms that lack any membrane-bound organelles which means that out of given options, only ribosomes are present in them. 

The nucleus is the largest and most significant living organelle of the cell. All the cellular activities of the cell are regulated by the nucleus. Hence it is called brain or control centre of the cell. The nucleus is surrounded by a double unit membrane from all sites. The chromosomes and genes which have genetical characters and transmit from one generation to another are found in the nucleus. Thus option D is the correct answer. 

The nucleus is an important cell organelle. It is the repository of genetic material. Inside nucleus, there is a synthesis of mRNA which is subsequently transported to the cytoplasm for protein synthesis. Thus, nucleus controls proteins synthesized in a cell and also is a repository of genetic material. Hence, the nucleus is controlling centre of the cell.

'Karyon' refers to the nucleus and 'logy' stands for systematic study. Hence, Karyology is the study of the nucleus. It can be defined as a cytological study of the cell nucleus, especially regarding the chromosomes.

Bacteria and cyanobacteria are prokaryotes, i.e., having pro or primitive karyon. These cells have primitive nucleus, not having a distinct nuclear membrane. These cells have a single circular molecule of DNA as genetic material but it is not present inside membrane bound nucleus.

Nucleo-lemma is a term used in parallel with plasma-lemma. The nucleo-lemma is a part of the nuclear membrane. The outer membrane may have ribosomes and interconnections with ER. Nuclear membrane has a large number of pores for the nucleo-cytoplasmic exchange of materials.

Prokaryotic cells like bacteria have a single circular DNA molecule as their genetic material which is also called as a bacterial chromosome. The eukaryotic cells have a prominent nucleus with species-specific number of linear chromosomes having well-defined centromere and telomeres.

• The nucleus controls protein synthesis and is the genetic repository of a cell. 
• Hence, the nucleus can be called as the mastermind of cell.
• Thus, option C is correct.

rDNA (ribosomal DNA) is located in the Nucleolar Organizer Region (NOR) of the chromosomes, which is the site where the nucleolus is formed.

Because of the lack of nuclei and organelles, mature red blood cells do not contain DNA and cannot synthesize any RNA, and consequently can not divide and have limited repair capabilities. 

The nucleus is a membrane-bound structure which is separated from the cytoplasm. This membrane is a nuclear membrane which has small pores which allow diffusion. The nucleolus is the centre dark part of the nucleus which is not surrounded by any kind of membrane. It is distinguished from nuclear material by its colour only.

The Nucleus is the largest cell organelle which contains the chromosomes. The nucleus has a nuclear membrane which is made up of two layers i.e it is and organelle with a double-membrane.

The nucleus is considered as the control center of the cell as it has all the information for controlling the various components of the cell and keeping the cell alive.

Nuclear membrane is a double layered membrane, made up of lipid bilayer and proteins that separates the nucleus from the rest of the cell. The cytoplasm contains the most of the hydrolytic enzymes, which can affect the genetic material. The membrane protects the genetic material from different chemical reactions. It decides what to enter and exit from the nucleus by acting selectively permeable. It also provides structural support to the nucleus.

Nuclear pores  are the passage through which movement of RNA and protein molecules takes place between nucleus and cytoplasm.

• The living matter of cell is protoplasm which is the colorless material composed of a mixture of small molecules such as ions, amino acid etc.

• The nucleus of a cell is separated from the cytoplasm by a double membrane known as the nuclear envelope.
  
• Prokaryotes do not have genomic DNA that is concentrated and localized to a small area within the cell called nucleoid region, thus it is absent in them.

• Whereas, a eukaryotic cell contains all the organelles and nucleus which is separated from the cytoplasm by the nuclear envelope.
• The correct answer is OPTION C.

The thread like structure present in the nucleus are called the chromosomes or the chromatin, when the degree of condensation is very less.

• RNA is found everywhere- nucleus, nucleolus, mitochondria, chloroplasts, ribosomes, cytoplasm, etc. RNAs are 3 different types- mRNA, tRNA and rRNA. mRNA and tRNA are found in the cytoplasm and rRNA in the nucleus.
• The ribosomes can be free within the cytoplasm of a cell or attached to the endoplasmic reticulum but do not present inside the nucleus. RNA and ribosomes act together resulting in the synthesis of proteins.

• The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life. 
• Cells are often called the "building blocks of life". 
•  Cells are of two types: eukaryotic, which contain a nucleus, and prokaryotic, which do not. 
• Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular. 
• Hence, the cell of all living organisms have a nucleus is correct.
• So, the correct answer is 'cell of all living organisms has a nucleus'.

Within the nucleus is a small subspace known as the nucleolus. It is not bound by a membrane, so it is not an organelle. This space forms near the part of DNA with instructions for making ribosomes, the molecules responsible for making proteins.

The nucleolus is a non-membrane-bound structure within the nucleus, whereas mitochondria, plastids, and the endoplasmic reticulum are membrane-bound organelles found in the cytoplasm.

Nucleus is a double membrane covered protoplasmic body that contains heredity information. With the help of grafting experiments on Acetabularia, Hammerling (1953) proved that nucleus is a storehouse of hereditary information.

The nucleus is two layered structure, it is a membrane-enclosed structure found in eukaryotic cells. It contains most of the cell's genetic material. The function of the nucleus is to maintain the integrity of the genes and to control the activities of the cell by regulating gene expression.

The nucleus is the most important and the largest component of the cell. Nucleus regulates the four main functions of the cell which are protein synthesis, cell division, growth and differentiation are carried out by the nucleus. Nucleus regulates all these cellular activities by controlling the enzymes required for cellular processes. Enzymes are proteins and protein synthesis is controlled by nucleus as mRNA required for protein synthesis is made from DNA which is situated in the nucleus.

The nucleolus is the largest structure present in the nucleus. Ribosome synthesis and assemblage occurs in nucleolus region. 
Chromosomes are not present in the cytoplasm. 
Golgi apparatus does not possess chromosomes. 
The nucleus is the double membrane bound structure of the cell in which most of the genetic material is present in the form of chromosomes. The nucleus is present in eukaryotic cells. Thus, the correct answer is option A.

The nucleus is the membrane bound important structure of the cell. Nucleus regulates all the cellular activities by controlling the enzymes required for cellular processes. It contains genetic information in the form of genes located in the chromosomes. It brings about growth of the cell by directing the synthesis of structural proteins. It also controls all the metabolic activities of the cell.
So, the correct answer is option D.

Deoxyribonucleic acid (DNA) encodes the genetic instructions which are used in development and functioning of all living organisms. Ribonucleic acid (RNA) is one of the types of nucleic acid. Both, DNA and RNA are found in the nucleus. DNA is involved in coding the genetic information. It is present in the nucleoplasm of the nucleus in the tightly coiled form called as chromosomes. RNA is present in the nucleolus of the nucleus and involved in protein synthesis.
So, the correct answer is option A.

Nucleus is the membrane bound structure of the cell. It contains the majority of the cell's genetic material, i.e., DNA in the form of DNA-protein complex called as chromatin. DNA is present in the nucleoplasm of the nucleus in the tightly coiled form called as chromosomes. 
So, the correct answer is option A.

The nucleus is the largest and important part of the cell. It surrounded by the two layers of membrane. These membranes separates the nuclear content to get mixed with cytoplasm. Cytoplasm is the proteinaceous fluid in the cell which holds organelles like ribosomes, mitochondria, ER etc. Thus, the correct answer is option B.

A nuclear membrane, also known as the nuclear envelope, is a double lipid bilayer membrane, which surrounds the nucleus containing genetic material and nucleolus in eukaryotic cells. The nuclear membrane consists of two lipid bilayers- the inner nuclear membrane and the outer nuclear membrane and consists pores called as nuclear pores for the transportation of DNA, RNA and proteins. Thus, the correct answer is option B.

A chromosome is a thread-like structure which is made of DNA tightly coiled many times around protein core made of histone proteins. Histone protein supports and stabilizes the structure. They are found in the nucleoplasm of the nucleus. They are absent in cytoplasm, lysosome, and ribosome. 

The nucleus controls the functioning of a cell. It is generally located in the center of the cell and is spherical in shape. It has a double-walled membrane which separates it from the cytoplasm. It contains the genetic material DNA and RNA in it. This porous membrane allows the transfer of material in the nucleus and cytoplasm. The nucleus contains a dense body called as nucleolus, which actually contains chromosomes, the genetic material. 

The nucleus is the membrane bound important structure of the cell. Nucleus regulates all the cellular activities by controlling the enzymes required for cellular processes. Enzymes are proteins and protein synthesis is controlled by nucleus as mRNA required for protein synthesis is made from DNA which is situated in the nucleus. It controls all the cellular activities and thus, called as brain of the cell.

Golgi apparatus is an organelle present in the cell and structurally possess series of compartments. Golgi apparatus has the main function of modifying, sorting and packaging the proteins which are synthesized by cells. Golgi bodies are also involved in the transport of lipid molecules across the cell. Golgi bodies also create lysosomes.  
Mitochondria produce the energy in the form of ATP of the cell. It consists its own DNA and called as mitochondrial DNA and not the DNA of the cell.
The nucleolus is the largest structure present in the nucleus. Ribosome synthesis and assemblage occurs in nucleolus region. The nucleus is bound with the double membrane in a eukaryotic cell in which most of the genetic material is present. The genetic material contains DNA and RNA. Thus, the correct answer is option D.

Nuclear membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus.

A eukaryotic cell has a nucleus bounded by a double wall membrane structure known as a nuclear membrane. The nuclear membrane is a discontinuous membrane having nuclear pores, which act as a protein channel for regulating the exchange of materials between cytoplasm and nucleoplasm. The gap between the inner and outer membrane is known as perinuclear space.

Chromatin is a complex of DNA and proteins that form chromosomes within the nucleus of eukaryotic cells. Nuclear DNA does not appear in free linear strands. 

A- As nucleus contains the genetic material responsible for hereditery. 

The nucleus is the important structure of the cell and fully enclosed in a nuclear membrane. It contains the cells' genetic material organized as DNA and variety of proteins to form chromosomes. This is major site for cell reproduction. The genes are first transcribed, where DNA is read by RNA polymerase to produce messenger RNA (mRNA). The nucleus is therefore the site of RNA and DNA synthesis. Whereas protein is synthesized from the mRNA in the cytoplasm. Thus, the correct answer is option D.

Acetabularia consists of a rootlike holdfast, a long, cylindrical stalk; and a cuplike cap. The nucleus is present in the holdfast. Acetabularia exhibits regeneration of the cap after any injury. A. mediterranea has a smooth cap and A. crenulata, has a cap with fingerlike projections. Danish biologist J. Hämmerling and Belgian biologist J. Brachet performed grafting experiment on above mentioned species and showed that type of caps that regenerated were determined by the type of the donor species of the holdfasts, not by those donating the stalks. It was concluded, that nucleus in the holdfast of Acetabularia controls the shape of the caps. The correct answer is E.

The eukaryotic endomembrane system has a nuclear membrane, endoplasmic reticulum, Golgi apparatus, plasma membrane and various small vesicles which are constantly reorganized and serve to segregate specific metabolic processes and to provide surfaces for enzyme-catalyzed reactions.
So, the correct answer is option A.

• A karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell. The term is also used for the complete set of chromosomes in a species or in an individual organism. The study of whole sets of chromosomes is sometimes known as karyology. Hence, the karyology is the study of the nucleus.
  
• So, the correct answer is 'nucleus'.
  

Answer is option (A) Acetabularia by Hammerling.

• A nucleus is a membrane-bound organelle containing the genetic material in the form of DNA molecule coiled to form the chromosomes.
  
• It is also known as the control centre of the cell.
• Within the nucleus, the DNA molecule gets transcribed into an mRNA template which is translated into a variety of proteins. 
  
• These translated proteins help in performing all the important functions within the cell.
• It was discovered by Robert Brown in the year 1831.
• So, the correct answer is 'Robert Brown'.

• Nucleus is a membrane-bound organelle containing the genetic material in the form of DNA molecule coiled to form the chromosomes.
  
• It is also known as the control centre of the cell.
• The DNA molecule gets transcribed into an mRNA template which is translated into a variety of proteins. 
  
• These translated proteins help in performing all the important functions within the cell.
• So, the answer is 'Nucleus'.

• The nuclear membrane or karyotheca is a double membrane having pores at intervals.
• The nuclear membrane on its inside has a supporting membrane called the nuclear lamina or the fibrous lamina having a uniform thickness.
• It is a dense network of fibres present inside the nucleus of cells and are made up of intermediate filaments and membrane-associated proteins.
• It provides mechanical support to the nucleus and also regulates DNA replication and cell division 
• So, the correct answer is 'Both B and C.'

• A nucleus is a membrane-bound organelle containing the genetic material in the form of DNA molecule coiled to form the chromosomes.
  
• The nuclear membrane or the nuclear envelope is a lipid bilayer membrane (porous double-membrane) that encloses the nucleus.
  
• Nuclear membranes have protein-based channels known as nuclear pores which allow the transport of molecules across the nuclear envelope.
• So, the correct answer is 'Porous double membrane'.

• Hammerling's nucleocytoplasmic experiments state that the cytoplasm is the centre for all the metabolic activities in the cell and the nucleus is the controlling centre. 

• This experiment was conducted using Acetabularia.

• Acetabularia is a genus unicellular or single-celled green algae belonging to the family Polyphysaceae which are found in subtropical waters.

• They are gigantic in size and complex in form, therefore, used in experiments in cell biology.

• So, the correct answer is 'Acetabularia'.

• Chromatin material which remains condensed during interphase is called heterochromatin.
  
• Heterochromatin refers to the certain regions of DNA found on the chromosomes of a eukaryotic cell.
  
• The heterochromatin gets darkly stained due to the highly condensed nature of the DNA in these regions and has higher ribonucleic acid content.
• This heterochromatin is made up of high copy number tandem repeats (repetitive nucleotides).
• So, the correct answer is 'Heterochromatin'.

• The DNA present in the nucleus undergoes transcription to form the messenger RNA or mRNA.
  
• The mRNA formed within the nucleus is transported out of the nucleus and into the cytoplasm of the cell and gets attached to the ribosomes. 
• It then synthesis proteins in the cytoplasm which is required by the cell for various cellular activities.
• So, the correct answer is 'RNAs'.

• Messenger RNA is formed in the nucleus.
  
• The process by which mRNA is formed from the DNA present in the nucleus is called transcription.
• The mRNA formed within the nucleus is transported out of the nucleus and into the cytoplasm of the cell and gets attached to the ribosomes. 
• It then synthesis proteins in the cytoplasm which is required by the cell for various cellular activities.
  
• So, the correct answer is 'Nucleus'.

• The mitochondria is a double-membraned cell organelle, known as the powerhouse of the cell which is present in all eukaryotic cells.
  
• The nucleus is enclosed by the nuclear envelope which is a double-layered membrane that consists of nuclear pores to regulate the transportation of substances such as RNA into and out of the nucleus. 
• The chloroplast is also covered by a double membrane which is known as the chloroplast envelope.
• So, the correct answer is 'Mitochondria, nucleus and chloroplast'.

The nucleus contains a viscous liquid called nucleoplasm. It contains chromosomes and nuclei. It is surrounded by a nuclear membrane and it helps in the exchange of material between nucleus and cytoplasm. So, the correct answer is option B.

Algae are a very large and diverse group of eukaryotic organisms, ranging from the microscopic unicellular Chlorella and the diatoms to giant multicellular kelps, the large brown alga. Diatoms are algae (most commonly known as phytoplanktons) with secondary chloroplasts derived from an endosymbiotic red alga. Yeats is also a eukaryote belonging to the kingdom Fungi. However, the Blue-green algae or Cyanobacteria is the most primitive photosynthetic bacteria (prokaryotic- the absence of well-defined nucleus) cell which is quite small and usually unicellular, though they often grow in colonies large enough to see.
Hence, the correct answer is option A.

DNA is a long polynucleotide strand, coiled to make chromatin fibres to fit into the cell. It also helps to prevent DNA damage. It is situated in the nucleus. 

There are three major functional parts of the cell such as plasma membrane, cytoplasm and nucleus. Plasma membrane regulates the particles entering or leaving the cell. It carries out endocytosis, exocytosis and transport of various substances through different carrier proteins. It is also involved in cell signaling. 
Cytoplasm is a gel-like substance present in all cells. All of the cell organelles are suspended in the cytoplasm. Most of the cellular activities as metabolic pathways like glycolysis, key processes like cell division occur in the cytoplasm. Nucleus regulates all the cellular activities by controlling the enzymes required for cellular processes. The four main cellular functions of the cell are protein synthesis, cell division, growth and differentiation are carried out by the nucleus. 

So, the correct answer is option A.

Steroid hormone receptors are found in the nucleus and cytosol. They are intra-cellular receptors responsible for the process of signal transduction. 

Sieve tubes are cells of phloem found in certain plants and help in long distance translocation and distribution. Their nucleus is fragmented and disappeared. Mammalian erythrocytes also called as red blood cells are formed in bone marrow from multipotential hemocytoblast and further converted to erythroblast (normoblast). The nucleus and mitochondria of erythroblast disappear and it is converted to mature erythrocyte with haemoglobin. Erythrocytes cannot multiply as they lack the nucleus and can survive for 100-120 days. Monocytes are immune cells of the human body and are capable of dividing into macrophages. So they have the well-defined nucleus. So nucleus is absent in sieve tube cells and mammalian erythrocytes.

The nucleus is membrane-bound organelles which are seen under a light microscope because of its large size. These are spherical in shape and encompasses nuclear membrane, chromosomes, nucleoplasm and nucleolus. It contains the cell's genetic material.

The nuclear envelope is a membrane barrier that separates the nucleus from the cytoplasmic in eukaryotic cells. It contains a large number of proteins. The nuclear envelope is composed of two concentric bilayer membranes. The two layers are fused together into numerous tiny holes called the nuclear pores.

The nucleus is a spherical organelle which is present in eukaryotic cells. The main function of the nucleus is to control gene expressions. It synthesizes RNA and DNA. Protein synthesis takes place in Ribosomes in the cytoplasm

Ribosomes are synthesized in the nucleolus but function in the cytoplasm. Therefore, functioning ribosomes are not found within the nucleus.

• Acetabularia is a genus unicellular or single-celled green algae belonging to the family Polyphysaceae which are found in subtropical waters.
  

• They are gigantic in size and complex in form, therefore, used in experiments in cell biology.
• Hammerling's nucleocytoplasmic experiments state that the cytoplasm is the centre for all the metabolic activities in the cell and the nucleus is the controlling centre. 
  
• So, the correct answer is 'Unicellular uninucleate green alga'.