What is a gene short definition?

 What is a Gene?

A gene is a region of DNA that is made up of a specific sequence of nucleotides, which codes a specific polypeptide chain. A nucleotide sequence of genes in DNA specifies the amino acid sequence of proteins through the genetic code. 

A set of three nucleotides known as codons each corresponds to a specific amino acid e.g., if a polypeptide chain has 100 amino acids then the number of nucleotides in a gene will be 300.

Types of RNA:

There are three mains of RNA which are synthesized from different parts of DNA in a process called transcription and then are moved out in the cytoplasm to perform specific functions.

The main three types are mRNA, tRNA, and rRNA.

Messenger RNA:

The mRNA is a type of RNA that carries information from DNA to the ribosomes, the site of protein synthesis in a cell. The coding sequence of mRNA determines the amino acid sequence in the protein that is to be produced. 

There are many types of mRNA because, for the translation of every polypeptide chain, a specific mRNA is required. (mRNA is about 3-5% of the total RNA of the cell).

Transfer RNA:

The tRNA is a small RNA chain of about 80 nucleotides that transfers a specific amino acid to the growing polypeptide chain at the ribosomal site of protein synthesis. There are at least 20 types of tRNA in each cell because, for each amino acid, a separate transfer RNA is required. About 60 types of tRNA have been identified so far. 

Transfer RNA is about 15% of the total RNA of the cell.

Ribosomal RNA:

The rRNA is the catalytic component of the ribosome. It is synthesized by the genes present in the DNA of several chromosomes found within the region of the nucleus called the nuclear organizer.

 The base sequence of rRNA of all organisms is similar thus there is only one type of rRNA. It is most abundant in about 80% of the total RNAs of the cell.

2.7 Conjugated Molecules

Conjugated molecules are types of molecules that are formed by the combination covalently with protein, a more complex molecule is formed called glycoprotein. Some of two different classes of molecules e.g., when carbohydrate molecule combines Lipoproteins: 

The lipoprotein forms when the lipid combines with protein. These types of molecules are frequently found in cell membranes and other types of membranes other examples of conjugated molecules are as under. cell-like mitochondria, endoplasmic reticulum, nuclear membrane, etc.

Nucleoproteins: 

It is formed by the combination of nucleic acid with protein e.g., Ribosomes and chromosomes of eukaryotes are basically nucleoproteins in composition. touched with glucosidic bond. 

Glycolipids: 

These are lipids with carbohydrate molecules that are part of the cell membrane.

SUMMARY

Hydrogen, oxygen, carbon, and nitrogen constitute more than 97% of the atoms in the human body.

Water is an important compound for life and its proper functioning is due to its polarity, low density in ice form, high heat of vaporization, high heat capacity, and cohesive and adhesive properties.

Chemically, carbohydrates may be defined as optically active polyhydroxy aldehydes or ketones or the compounds that produce such units on hydrolysis. Carbohydrates are classified into three subtypes: monosaccharides, oligosaccharides, and polysaccharides.

Many of the large sugar units (> C5) tend to form ring structures in solution. The ring is formed by the reaction of the aldehyde or keto group with one of the OH- groups.

The joining of two to ten monosaccharides forms an oligosaccharide. One or more glycoside linkages hold the monosaccharides together. The simplest, and most common, oligosaccharides are the disaccharides.

A covalent bond is formed between a carbohydrate molecule and a known as a glycosidic bond.