Chromosomes are found in the nucleus during the M-phase of the cell cycle. Let us explore more in the below.
Nucleus have chromosome structure formed when the cell is about to divide. All the genetic information of the cell is stored in chromatin fibres. These chromatin fibres will condense and form chromosome that act as a hereditary unit.
Nucleus is the most specialized and largest organelle of the cell. Chromosomes are rod-shaped, thread like, oval or dot-like in shape with a size of 0.5-30.0μm in length and 0.2-3.0μm in breadth.
Is nucleus and chromosome the same?
Chromosomes are the part of the nucleus. Let us find out how they are different from each other.
Chromosomes and nucleus are different from each other. Nucleus is a double membrane bound organelle, which contains chromatin fibres that condense to form chromosomes during cell division and reproduction.
Nucleus is the largest cell organelle found in all eukaryotic cells except in erythrocytes. Basically, a cell posses only single nucleus but in case of Paramecium, it contains more than two nucleus depending upon the species.
Why does nucleus have chromosomes?
Nucleus contains chromosomes to perform various functions. The exact reason of nucleus having chromosome is discussed below.
Nucleus does have chromosomes as it controls cellular metabolism and plays a crucial role in transmitting the genetic information from one generation to another. Chromosomes are the condensed form of chromatin reticulum which contains genetic information to distribute equitably to the progeny.
During cell division or reproduction, all the genetic information is enclosed in the nucleus in the form of chromosomes. These chromosomes gets divided during cell cycle and pass on the information to daughter cells.
Relation between nucleus and chromosome
Chromosome and nucleus are related to each other in many aspects. Lets us find out more information about them.
Nucleus contains chromosomes which are condensed from chromatin fibres. During cell division, chromosomes are equally arranged at both the poles of nucleus . Chromosomes splits into two halves called chromatids during cell division.
When chromosomes are equally distributed at the poles on nucleus, firstly nucleus divides and then cytoplasmic division occurs to form two daughter cells from parent cell.
How many chromosomes do nucleus have?
Nucleus contains exactly the same number of chromosomes in each cell. The actual number for human chromosome is given below.
There are total 46 chromosomes present in every nucleus. All the cells of a body possess the same number of chromosomes. Gametes and haploid phases possess one set of chromosomes or single genome where there is one chromosome of each type.
In homo sapiens, they have two types of chromosomes, autosomes and allosomes. 22 pair are of autosomes and one pair is of allosomes that determines the gender of the person.
Does every nucleus have 46 chromosomes ?
There are many organisms present in the nature that contain 46 chromosomes. Here are some examples of given for the number of chromosome present in the nucleus.
Every nucleus does not have 46 chromosomes. Nucleus of human cell and some other organisms contains 46 chromosomes or 23 pairs of chromosomes. But the number of chromosomes vary depending upon the type of organisms.
Like, zebra fish have 50 chromosomes, sheep has 54, silkworm has 56, elephant has 56, cattle contains 60, brown bear has 74, dog contains 78, pigeon has 80, red king crab has 208 and ciliated protozoa possess 16000 chromosomes.
Does the nucleus of a plant cell have chromosomes?
Every eukaryotic cell contains nucleus and cell division occurs only if chromosomes are formed. Let us explore more about plant cell nucleus.
Nucleus of a plant cell have chromosomes. Chromosomes are only visible during the cell division stage, before it is packed in the form of chromatin fibres or DNA wrapped around the histone proteins called nucleosomes.
Apart from this, plant cell has mitochondria and chloroplast that also contains DNA or chromosomes.
Does the nucleus of an animal cell have chromosomes?
Animal cell have well defined nucleus and chromosomes number in every eukaryotic cell varies depending upon species and organism type. Let us understand below.
Nucleus of an animal cell contains chromosomes. The number of chromosomes vary in animal species. Human contains 23 pair of chromosomes or 46 chromosome in total and number of chromosome is same in each cell. All the cells of a body possess the same number of chromosomes.
Gametes and haploid phases possess one set of chromosomes or single genome where there is one chromosome of each type. In somatic cells of animals and higher plants there are two genomes or two sets of chromosomes of each type. They are called homologous chromosomes.
Why does nucleus of an animal cell not have chromosomes?
If a cell is eukaryotic, it definitely contains chromosomes in their nucleus. Let us check out possible ways for the animal cell for not having chromosomes.
It is not possible for a eukaryotic cell for not having chromosomes because every eukaryotic cell contains nucleus. But there are some exceptions like RBC of mammalian cells are devoid of nucleus in order get more hemoglobin so that they can transport more amount oxygen to the body.
Sieve tube element loses its nucleus at maturity because companion cells controls the function of sieve tube element.
Difference between Chromatin and chromosome on the basis of their morphology and functions
The term chromatin and chromosome are closely related to each other. But they are quite different in their morphology and functions. Let us explore more about their differences.
|Definition||Chromatin is the entire genetic material consists of fine fibrils.||Chromosome is a unit of genetic material and are thick short rods.|
|Condensing||It is highly uncondensed genetic material.||It is condensed genetic material.|
|Cell cycle phase||It occurs in interphase of the cell cycle.||It is formed during M-phase of the cell cycle.|
|Active Genes||Chromatin is present with active genes.||Only giant chromosomes contains active genes.|
|Function||It is responsible for cell metabolism, differentiation and growth.||It is only responsible for the equal distribution of the genetic material to the progeny.|
Functions of Nucleus
Nucleus of eukaryotic cell is considered as a brain of that cell which controls and performs various functions as mentioned below –
- All the genetic information of the cell is stored in the nucleus.
- Nucleus controls all the cellular activities and helps in transmission of the characters from one generation to the next.
- Nucleus controls the division of cell. During a cell division, nucleus divides first then cytoplasmic division occur.
- All the genetic information is stored in chromatin fibres and complete cell receives the instructions from the nucleus only.
- Nucleus also helps in controlling the synthesis of essential enzymes used for the metabolism of the cell.
- Nucleolus is the site for the formation of ribosomes.
- Variations occurs due to changes in the genetic material contained in the nucleus.
What is the position of nucleus inside the cell?
The position of nucleus inside the cell is different in plant and animal cell. The exact location of plant and animal cell is given below.
The position of the nucleus often lies at the centre of the cell as it is responsible for controlling all the activities of cell and other cell components. Location of nucleus also depends on the cell metabolic activities. Nucleus occurs in that area where metabolic activity is high.
But in case of plants, nucleus lies at the periphery of the cell because there is presence of large central vacuole. In adipocytes, nucleus lies at the periphery due to presence of fat drop in the centre. In some cases, Spirogyra has nucleus situated inside the central vacuole.
Parts of Nucleus
Each part of nucleus plays a role a unique role in cellular metabolism and other activities of the cell. The main parts of nucleus are discussed below in brief.
A typical nucleus is divided into five parts : Nuclear envelope, Nuclear matrix, Nucleoplasm, Chromatin and Nucleolus. Nuclear envelope is double membrane covering.
- The outer membrane is associated with endoplasmic reticulum which may contains ribosomes attached on it.
- Nucleoplasm is a transparent non staining substance usually contains number of chemicals like nucleotides, proteins, enzymes.
- Nuclear matrix is a fine network made of proteinaceous fibrils that spreads throughout the nucleus.
- Chromatin reticulum is a fine long thread like structures that overlaps to form chromatin reticulum which stores the genetic information.
- Nucleolus is a naked irregularly rounded structure present inside the nucleus and usually attached to chromatin at a specific site called nucleolar organizer region. A nucleus may contain 1-4 nucleoli.
Nucleus contain chromosomes and nucleus is present in all eukaryotes except erythrocytes and sieve tube element of plants. Nucleus is a double membrane bound organelle, which contains chromatin fibres that condense to form chromosomes during cell division and reproduction. Nucleus controls all the cellular activities and helps in transmission of the characters from one generation to the next.