GENEITCS

What is DNA?

DNA (deoxyribonucleic acid) is an extended molecule housed within nearly all our cells in a compartment known as the nucleus. The information in DNA is encoded through four chemical bases—adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA comprises around 3 billion bases, with over 99 percent of these bases being identical in all individuals. It is the sequence of these bases that dictates the information available for constructing and sustaining an organism. DNA bases pair up with each other, A with T and C with G, forming units known as base pairs. Each base is also linked to a sugar molecule and a phosphate molecule, collectively referred to as a nucleotide. Nucleotides are organized into two lengthy strands, creating a double helix spiral. The double helix takes on a ladder-like structure; the base pairs constitute the rungs, while the sugar and phosphate molecules form the vertical sidepieces of the ladder. A segment of DNA, millions of base pairs long and associated with certain proteins, is recognized as a chromosome. One of the marvels of DNA is its ability to replicate itself. Each strand of DNA in the double helix can act as a template for duplicating the sequence of bases. This replication is crucial during cell division because each new cell must possess an exact copy of the DNA present in the original cell.

What are Genes?

A gene is a minute segment of a DNA strand. The sequence of DNA bases within a gene provides instructions for synthesizing molecules known as proteins. Proteins serve as the foundational components of all life forms, and each protein performs a specific function in the body. Human genes exhibit variation in size, ranging from a few hundred DNA bases to over 2 million bases. It is estimated that humans possess between 20,000 and 25,000 genes. Each individual possesses two copies of every gene, with one inherited from each parent. While most genes are uniform across all individuals, a limited number of genes exhibit slight variations among people. These minor differences contribute to the distinct physical features and tendencies of each person. In essence, your genes contain the instructions for constructing every aspect of you: your eye, hair, and skin color, your propensity to gain weight, your athletic inclinations, your likelihood of developing addictions or diseases, and your other unique characteristics.

What is a Chromosome?

Chromosomes are lengthy DNA strands organized into filamentous structures. They reside in the nucleus (core) of each cell. Each chromosome consists of DNA tightly wound around proteins known as histones. Every chromosome possesses a specific juncture called the centromere, dividing the chromosome into two segments or "arms." The shorter arm of the chromosome is designated the "p arm," while the longer arm is labeled the "q arm." The placement of the centromere on each chromosome imparts the chromosome with its distinct shape and can be employed to elucidate the location of particular genes.

DNA Mutations

As previously mentioned, each gene is composed of a sequence of bases, and these bases provide instructions for creating a single protein. Any alteration in the sequence of bases and thus in the instructions is termed a mutation. Some mutations have minimal or no impact on the protein, while others render the protein nonfunctional. A gene mutation denotes a lasting change in the DNA sequence constituting a gene. Mutations range in size from a single DNA base to a sizable segment of a chromosome. Gene mutations can be inherited from a parent or acquired during an individual's lifetime. Mutations transmitted from parent to child are hereditary mutations, persisting throughout a person's life in nearly every cell in the body. Mutations occurring solely in an egg or sperm cell, or immediately after fertilization, are referred to as new (de novo) mutations and may account for genetic disorders in which an affected child bears a mutation in every cell but lacks a family history of the disorder. Acquired mutations transpire in the DNA of individual cells at some point during a person's life. These changes can be induced by environmental factors such as ultraviolet radiation from the sun. Acquired mutations in cells other than eggs or sperm cannot be inherited by the next generation. Certain genetic alterations are exceedingly uncommon, while others are prevalent. Genetic changes affecting more than 1 percent of the population are termed polymorphisms. They are prevalent enough to be considered a typical variation in the DNA. Polymorphisms underlie many normal distinctions among individuals, such as eye color, hair color, and blood type.

Inheriting Genes

Humans receive 23 chromosomes from each of their parents, resulting in a sum of 46 chromosomes. Of these, 44 chromosomes are shared between both men and women and are known as autosomes. The remaining two are the sex chromosomes, denoted as X and Y. Females inherit two X chromosomes, while males inherit one X chromosome from their mother and one Y chromosome from their father. The amalgamation of the genes we receive determines specific traits that may mirror those of our mother and others that mirror those of our father.