Genetics is a branch of natural science that deals with heredity due to the transmission of genes, gene regulation, and gene manipulation.
Homozygous Definition Homozygous is a genetic condition where an individual inherits the same alleles of a gene from both the parents. In homozygous chromosomes, both alleles are either dominant or recessive. The dominant trait is represented by two capital letters … Read more
Heterochromatin Definition Heterochromatin is a tightly packed or condensed DNA that is characterized by intense stains when stained with nuclear stains, containing transcriptionally inactive sequences. It exists in multiple variations, up to four to five state, each of which is … Read more
Chromosome Definition A chromosome is a thread-like structure present in the nucleus or nuclear region of the cytoplasm that is made up of a single molecule of DNA (Deoxyribonucleic acid) and proteins, carrying some or all genetic materials of an … Read more
Phenotype Definition Phenotype is a term used in genetics to refer to all the observable traits in organisms as a result of the interaction of the genotype with the environment. The term ‘pheno’ in ‘phenotype’ refers to ‘observe’ and thus … Read more
Natural selection definition Natural selection is a process of adaptation by an organism to the changing environment by bringing selective changes to its genotype or genetic composition. Natural selection is one of the four primary mechanisms of evolution, along with … Read more
Mendel’s Law of Dominance Definition Mendel’s Law of Dominance states that ‘In crossing between homozygous organisms for contrasting characters of a pair, only one character of the pair appears in the first generation.’ The law of dominance is the first … Read more
Mendel’s Law of Independent Assortment Definition Mendel’s Law of Independent Assortment states that ‘when the parents differ from each other in two or more pairs of contrasting characters, the inheritance of one pair of characters is independent of the other.’ In … Read more
Mendel’s Law of Segregation Definition Mendel’s Law of Segregation states that ‘The hybrids or heterozygotes of F1 generation have two contrasting characters of dominant and recessive nature where the alleles though remain together for a long time do not contaminate … Read more
In the 1860s, an Austrian monk named Gregor Mendel introduced a new theory of inheritance based on his experimental work with pea plants. Mendel believed that heredity is the result of discrete units of inheritance, and every single unit (or gene) … Read more
Punnett Square Definition The Punnett square is a table or checkboard grid that is used to determine all possible genotypes from a particular cross. Punnett square is a simple square divided into four quadrants which consist of all the possible … Read more
Dihybrid Cross Definition A dihybrid cross is a type of genetic cross between two individuals with either homozygous or heterozygous genotypes of two characters or traits. The dihybrid cross is different from the monohybrid cross, which only involves a single … Read more
Monohybrid Cross Definition A Monohybrid cross is a type of genetic cross between two individuals with homozygous genotypes of a single character or trait, often resulting in an opposite phenotype. Monohybrid crosses are usually performed to determine the genotypes of … Read more
Image Source: Spencerbaron and YassineMrabet. Incomplete dominance definition Incomplete dominance is a mechanism of dominance in heterozygotes, where the dominant allele does not entirely overcome the phenotypic expression of the recessive allele, and there occurs an intermediate phenotype in the … Read more
Sex makes no difference in Mendel’s crosses. But the Mendel’s laws are not applicable on those genes which are exclusively located either in X or Y chromosome. Sex-Linked Inheritance is the inheritance of a trait (phenotype) that is determined by … Read more
Normally, a woman gives birth to only one young at a time, but sometimes more than one child are born to a woman at the same time. The delivery of more than one baby by a mother is termed as … Read more
The genetic code is the set of rules by which a linear sequence of nucleotides specifies the linear sequence of a polypeptide. That is, they specify how the nucleotide sequence of an mRNA is translated into the amino acid sequence … Read more
Though, the genes of nuclear chromosomes have a significant and key role in the inheritance of almost all traits from generations to generations, they altogether cannot be considered as the sole vehicles of inheritance. Certain experimental evidences suggest the occurrence … Read more
The Hardy–Weinberg principle, also known as the Hardy–Weinberg equilibrium, model, theorem, or law explains that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. The law was proposed by a British mathematician Hardy … Read more
The genome of an organism encompasses all of the genes of that organism. Gene is a distinct sequence of nucleotides forming part of a chromosome, the order of which determines the order of monomers in a polypeptide or nucleic acid … Read more
Each chromosome contains more than one gene. The genes for different characters may be either situated in the same chromosome or in different chromosomes. When the genes are situated in different chromosomes, the characters they control appear in the next … Read more
In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. Chromosomes were first described by … Read more