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Genetics is the science of heredity and variation in living organisms. Geneticists examine a wide variety of inherited traits, from fruit production in trees to metabolic diseases in humans. People who study genetics do so in a wide variety of situations, from research laboratories to pharmaceutical companies. New breakthroughs in this field are consistently being made.
What is DNA?
DNA, or deoxyribonucleic acid is a nucleic acid that
contains the genetic instructions used in the development
and functioning of all known living organisms. The main role
of DNA molecules is the long-term storage of information.
DNA is often compared to a set of blueprints or ,a recipe,
or a code, since it. It contains the instructions needed to
construct other components of cells, such as proteins and
RNA molecules.
Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups. Attached to each sugar is one of four types of molecules called bases. The four bases found in DNA are adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). It is the sequence of these four bases along the backbone that encodes information.
DNA is found in almost every cell within the human body from white cells in the blood to check cells in your mouth. Once the sequence of your DNA has been determined, it does not change over your lifetime.
What are Genes?
A gene is the basic unit of heredity in a living organism.
Genes hold the information to build and maintain our cells
and pass genetic traits to our offspring. A gene is a
segment of DNA that, taken as a whole, specifies a trait.
A gene is encoded in the sequence of the four bases (A, G, C and T) along the backbone of the DNA strand. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription.
Gene are determined by a portion of DNA that contains both “coding” sequences that determine what the gene does, and “non-coding” sequences that determine when the gene is active.
Inheritance
Inheritance is the passing of traits to offspring (from its
parents or ancestors). This is the process by which an
offspring acquires or becomes predisposed to the
characteristics of its parents. At its most fundamental
level, inheritance in individuals occurs by means of
discrete traits, called genes. Humans have two different,
discrete versions of the same gene called alleles.
Individuals with two copies of the same allele of a given
gene are called homozygous at that gene, while individuals
with two different alleles of a given gene are called
heterozygous at that gene.
The set of alleles an individual has for a specific gene is called its genotype, while the observable traits of an individual are called its phenotype. When individuals are heterozygous at a gene, often one allele is called dominant as its qualities dominate the phenotype, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once.
When individuals reproduce, their offspring randomly inherit one of the two alleles from each parent. Moreover, the alleles of different genes get shuffled between parents to form offspring with many different combinations. However, in cases of genetic linkage, alleles do not assort independently.
