See the image,The genes are located on chromosomes. Genes are the functional portion of our genome, approximately 3% portion of our genome encodes proteins.The gene is made up of the exonic and intronic regions in which the intronic regions are spliced out from the final gene product.“Alternative forms of a gene are called an allele.”To understand this, let’s take an example,Suppose one gene encodes for the eye color, let say it is EYE1 , thus different eye colors can be produced by alteration in this gene.Different alterations of EYE1 gene govern different eye color are called alleles. X-linked dominant vs X-linked recessive disorders: The gene is a coding DNA sequence that encodes a specific protein. Autosomal dominant vs Autosomal recessive: Single-gene disorders Vs Multi-gene disorders: Adenine and Guanine are the purines while the Thymine and Cytosine are pyrimidines bases present in DNA.Three hydrogen bonds between cytosine and guanine while two hydrogen bond between thymine and adenine joins two single-stranded DNA.For more detail on DNA please read our article: DNA story: The structure and function of DNA“A functional piece of DNA is called a gene.”

The central dogma… Replication:Replication is an enzyme-dependent process in which the double-stranded DNA molecules synthesizes four new single-stranded DNA. The RNA polymerase governed catalytic reaction is a de novo synthesis process.Primase: primase synthesizes a short stretch of DNA or RNA polynucleotide of 12 to 22nts called primer which later involves in replication (Read more: Primase).Helicase: helicase unwinds double-stranded DNA for initiating replication (Read more: Helicase).Topoisomerase: topoisomerase is a special class of enzyme releases the tension on the remaining dsDNA strand during replication (Read more: Topoisomerase).Ligase: it is an enzyme that fills the gap between the nucleotides by creating the phosphodiester bonds between them (Read more: Helicase).Read our article on DNA replication: The general process of DNA replication. Replication, transcription, and translation are collectively called a central dogma process.The central dogma process is governed by the enzymatic catalytic reaction in which different enzymes such as DNA polymerase, primase, helicase, topoisomerase, RNA polymerase, ligase and other enzymes govern each step by its specific effects.DNA polymerase: using the 3’ OH end, the DNA polymerase synthesizes new DNA strand during replication (Read more: DNA polymerase).RNA polymerase: RNA polymerase synthesizes an RNA strand during the process of transcription.

A long chain of amino acids builds a protein.Different types of structural and functional proteins are formed from the balanced processing of central dogma.Imbalance in any step of replication, transcription or translation results in the disease condition.Any alteration in the DNA sequence results in the mutation, a mutation may be either helpful or harmful to us.Read more on different types of mutations: Different Types Of Genetic Mutations.However, in the majority of cases, it is harmful and causes some inherited or non-inherited disease conditions.A heritable genetic portion of a genome that is responsible for a particular phenotype or trait is called a genotype.The observable traits of an organism originated due to the interaction between genotype or gene and the environment is called a phenotype.The genotype is a genetic entity of a particular trait while the phenotype is a visible or observable entity of a particular trail.Mitosis is a process of somatic cell division in which two daughter cells are formed with the same number of chromosomes.Contrary, the meiosis occurs in the germline cells in which a new cell generated from the parent cell having half or a haploid number of chromosomes.Thus the autosomal cells (all cells of our body, except the germ cells) have the exact 46 number of chromosomes while the germ cells have only haploid 23 number of chromosomes.A new organism is originated from the fusion of sperm and egg cell (germ cells), in which 23 chromosomes inherited from the father or male and 23 chromosomes inherited from the mother or female.As the chromosomes inherited, the genes located on the chromosomes also inherited from parents to their offsprings.In nature, new variations or more preciously we can say new genotypes are produced by the phenomenon called recombination.The exchange between the genetic material of two identical homologous chromosomes is called recombination.Recombination occurs during the meiosis thus a new variation inherited directly to the embryo and to the offspring.Related article: Introduction To Genetics: Definition, History, Applications And Branches Homozygous vs Heterozygous:The condition in which an individual inherited the same type of alleles is called Homozygous condition if it has two identical dominant alleles it is known as homozygous dominant or if it has two identical recessive alleles, it is known as homozygous recessive.The condition in which an individual inherited two different types of alleles, one dominant and one recessive, the condition is called heterozygous.In one of an autosomal recessive blood disorder called the thalassemia, the HB allele is autosomal dominant, the allele HB is recessive and responsible for disease conditions.The homozygous dominant condition is totally normal, do not show any sign of disease while the homozygous recessive condition is responsible for the occurrence of disease.However, in the heterozygous condition, the individual does not show any sign of the disease but it can inherit the disease allele to the next generation hence the condition is often known as carrier condition.Some organelles like mitochondria and chloroplast have their own DNA and own replication and transcription machinery.However, the DNA of it is not arranged on the chromosome, instead, it is arranged circularly called the circular DNA, some organelles also have linear DNA.“The process of replication and transcription occurs in the nucleus of a cell, once mRNA is transcribed, it is exported to the cytoplasm, at the ribosome, where the protein is synthesized.” What are genetic disorders?Genetic disorders are originated due to genetic mutations, chromosomal aberrations or epigenetic alterations.Genetic disorders that occur by birth and inherited to consecutive generations are called an inherited genetic disease.The inherited genetic disorders are of different types: Single-gene disorders Vs Multi-gene disorders:Genetic disorders are originated due to mutation or group of mutations in a single or group of genes.If the disease occurs dues to the mutation or mutations in a single gene. Three nucleotides create a codon and each codon encodes for one particular amino acid. Translation:The translation is a process in which the long chain of amino acid is formed from the mRNA. Transcription:Transcription is a process in which the mRNA is formed from the DNA having all the information for encoding a protein.

These disorders are also called polygenic disorders.Autosomal dominant vs Autosomal recessive:In the autosomal dominant condition, a single copy of a mutant allele is necessary to cause disease. For example, Diabetes or heart disease.

Basics Of Genetics