Question

What is a gene?

Short answer

Answer: A gene is the fundamental, physical, and functional unit of heredity that carries genetic information. It is a specific sequence of nucleotides within a DNA or RNA molecule, which encodes the synthesis of a specific protein or RNA molecule with a specific function in the cell. Genes play a critical role in determining the traits of an organism, such as its appearance, behavior, and physiological functions. They provide the instructions for creating all the proteins and RNA molecules within a cell, which are essential for the structure, function, and regulation of the body's tissues and organs.

Step-by-step solution

Introduction

A gene is the fundamental, physical, and functional unit of heredity. It is a specific sequence of nucleotides within a DNA or RNA molecule that carries the information to create a specific protein or RNA molecule with a specific function in the cell.

Structure of DNA

DNA (deoxyribonucleic acid) is the molecule that carries genetic information in most living organisms, including humans. It is composed of four types of nucleotide bases – adenine (A), guanine (G), cytosine (C), and thymine (T) - which form pairs and are held together by hydrogen bonds. DNA has a double helix structure, with two complementary strands running anti-parallel to each other.

Gene Composition

A gene is a specific sequence of DNA nucleotides that codes for a particular protein or RNA molecule. The number of nucleotides in a gene can range from just a few hundred to several million. The nucleotides in a gene determine the order of amino acids in a protein, while in RNA molecules, they encode for a specific type of RNA with a specific function.

Protein Synthesis

The process of creating proteins from genes is called protein synthesis. It involves two main steps: transcription and translation. During transcription, an enzyme called RNA polymerase reads the DNA sequence in the gene and creates a complementary mRNA (messenger RNA) molecule. This mRNA then moves from the nucleus of the cell to the cytoplasm, where it is read by ribosomes during translation. The ribosome reads the mRNA sequence in groups of three nucleotides called codons and adds the corresponding amino acids to a growing polypeptide chain, creating the protein specified by the gene.

Gene Expression and Regulation

Gene expression is the process by which the information stored in a gene is used to create a functional product, either a protein or a functional RNA molecule. The expression of a gene can be regulated in response to different factors, such as environmental conditions, cellular needs, or signaling molecules. This allows cells to control when and how much of a specific gene product is produced.

Function and Importance

Genes play a critical role in determining the traits of an organism, such as its appearance, behavior, and physiological functions. They provide the instructions for creating all the proteins and RNA molecules within a cell, which are essential for the structure, function, and regulation of the body's tissues and organs. Genes are passed down from parents to offspring, ensuring the continuity of genetic information across generations. The variation in genes between individuals gives rise to the diversity of traits within a species, allowing for adaptation to different environments and survival challenges.