Human genes

Human Genes

Human genes are fundamental units of heredity and are composed of DNA. They hold the instructions for the development, functioning, growth, and reproduction of all human cells. Human genes are located on chromosomes and are responsible for the genetic traits that are passed from parents to their offspring. The Human Genome Project, completed in 2003, revealed that humans have between 20,000 and 25,000 genes.

Overview

Each gene in the human genome is made up of a sequence of nucleotides within the DNA molecule. These sequences determine the structure of proteins, which carry out most of the work within cells. The study of human genes encompasses genetics, genomics, and molecular biology, focusing on gene structure, function, variation, and distribution.

Structure and Function

Human genes consist of coding regions, or exons, which specify the amino acid sequences of proteins, and non-coding regions, or introns, which may regulate gene expression. Genes are transcribed into messenger RNA (mRNA), which is then translated into a protein. The function of a gene is largely determined by the protein it encodes, influencing everything from physical characteristics to susceptibility to diseases.

Genetic Variation

Variations in human genes come from mutations, which can be inherited or occur spontaneously. Single nucleotide polymorphisms (SNPs) are the most common type of genetic variation among people. While many mutations are neutral, some can cause diseases or increase disease risk. Others may provide advantageous traits, contributing to human diversity.

Genetic Disorders

Some diseases are caused by mutations in single genes, known as Mendelian disorders, including cystic fibrosis and sickle cell anemia. Other diseases, like heart disease and diabetes, are influenced by multiple genes (polygenic) and environmental factors.

Genetic Research and Medicine

Research into human genes has led to advancements in genetic testing, personalized medicine, and gene therapy. Understanding genetic predispositions to diseases can aid in early diagnosis and tailored treatment plans. Gene therapy, still in its infancy, holds promise for treating or even curing genetic disorders by repairing or replacing faulty genes.

Glossary of Human Gene-related Terms

• Allele - One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
• Chromosome - A long DNA molecule with part or all of the genetic material of an organism.
• DNA (Deoxyribonucleic Acid) - The carrier of genetic information in humans and almost all other organisms.
• Dominant Allele - An allele that expresses its phenotypic effect even when heterozygous with a recessive allele.
• Exon - A segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.
• Gene Expression - The process by which the information encoded in a gene is used to direct the assembly of a protein molecule.
• Genetic Code - The set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins by living cells.
• Genome - The complete set of genes or genetic material present in a cell or organism.
• Heterozygous - Having two different alleles of a particular gene or genes.
• Homozygous - Having two identical alleles of a particular gene or genes.
• Intron - A segment of a DNA or RNA molecule that does not code for proteins and interrupts the sequence of genes.
• Mutation - The changing of the structure of a gene, resulting in a variant form that may be transmitted to subsequent generations.
• Phenotype - The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
• Polygenic - A trait or disorder that is influenced by multiple genes.
• Recessive Allele - An allele that produces its characteristic phenotype only when its paired allele is identical.
• SNP (Single Nucleotide Polymorphism) - A variation in a single nucleotide that occurs at a specific position in the genome.

Also see

• List of human genes

Human genes Resources
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