Study of genetics is gaining increasing popularity amongst students of science and researchers alike. It is an extension of biology.
Genetics is the study of genes. A gene is the basic unit of heredity. Genes are basically sections of DNA that are found on chromosomes. Heredity is the process by which parents pass on certain genes to their children. These genes govern certain traits such as physical appearance, medical conditions and also talent. Humans inherit chromosomes from their biological parents.
Did you know: Gregor Mendel, an Austrian scientist is considered as the father of genetics.
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Genetics biology terms
In order to understand genetics biology, you should be familiar with the following terms:
The different variations of a gene are referred to as alleles. These variations may or may not cause observable variations. In humans there are two alleles at each genetic locus, one inherited from each parent. Some organisms have multiple alleles at the genetic locus.
Dominant and Recessive Alleles
Humans have two alleles at each genetic locus and the interaction between the two can result in dominant and recessive alleles. The allele that shows up in the individual’s makeup is called the dominant allele while the allele that is shadowed is called the recessive allele.
Homozygous or heterozygous organisms
When an organism has two copies of the same allele for a gene it is said to be Homozygous (home means same). If it carries different alleles for a gene then it is said to be Heterozygous (hetero means different). Also in case of homozygous if the two copies are of the same dominant allele then the organism is homozygous dominant whereas if the two copies are of the same recessive allele then it is said to be homozygous recessive.
Genotypes and Phenotypes
Genotype is the genetic makeup of an organism. Also referred to as the genetic potential, genotype is the information contained within the two alleles at the genetic locus. Thus genotype represents the entire genetic information of a person. As some of this may not be observable, biological tests are needed to determine the genotype. Examples of genotype include skin color, hair color, height, certain inherited diseases and behaviors.
Phenotype on the other hand refers to the genetic traits that are observable. Examples of phenotype include height, hair color, eye color and so on.
Human genome is the complete set of nucleic acid sequence (that is 3.2 billion bases of DNA) and it contains all the genetic information for a person. It is the complete set of all the genetic instructions. Each living organism has a unique genome.
A genetic disorder is caused when there is abnormality in the person’s DNA.
Diseases such as Sickle cell disease, cystic fibrosis and polycystic kidney disease are caused due to mutation of a single gene. Such disorders are called as single gene or monogenetic disorders.
Complex genetic disorders are caused by mutations in more than one gene.
Chromosomal disorders are caused when there are missing or mutated chromosomes. Down’s syndrome is a chromosomal disorder which is caused due to an extra chromosome 21.
Did you know: There are more than 6000 known genetic disorders.
The only way to cure or treat a genetic disease is to alter the mutated DNA sequence in the genome of the person. This is referred to as gene therapy.
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