Genetics

Genetics is a branch of natural science that deals with heredity due to the transmission of genes, gene regulation, and gene manipulation.

  • Genetics is a connecting link between many disciplines like microbiology, biotechnology, medicine, and agriculture.
  • Studies involving genes and chromosomes of living beings began quite late as it requires significant advances in the microscopy area.
  • The influence of heredity and its application of cultivation and production improved organisms, however, had been recognized since ancient times.
  • The study of genes and genetics began as a major concept after studies made by Mendel on pea plants. It was further strengthened and flourished by the works of Morgan.
  • Eventually, genetics became a distinct area of study with the identification of genes and the study of genes at different levels, including their role in the cell, their regulation, and their expression.
  • Initially, genetics was limited to understanding the concept and process of heredity via techniques like the formation of Punnet’s square. With the development of techniques like X-ray diffraction, the structure of DNA, and the presence of genetic code were established. This paved the way for modern genetics.
  • Modern genetics focuses on the chemical composition of structures found in genes like the DNA that influences the chemical reactions taking place in the cell.
  • Gene expression is influenced by two major factors; the genetic composition and the influence of the environment.
  • The influence of the environment on gene expression can be distinctly observed in green plants where the gene responsible for the formation of chlorophyll is only expressed in the presence of sunlight.
  •  Genes, through the proteins they encode, determine how efficiently foods and chemicals are metabolized, how effectively toxins are detoxified, and even how vigorously infections are targeted.
  • Processes like mutations are now a significant cause of major genetic diseases. The mutations might arise due to a complex combination of genetic, behavioral, and environmental factors.

Dihybrid Cross- Definition, Steps and Process with Examples

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Dihybrid Cross

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 genetic character or trait. Dihybrid crosses are more complex than monohybrid crosses as these involve more than one genetic trait where the parents can be either homozygous or heterozygous for these traits. The dihybrid cross is used as a method … Read more

Monohybrid Cross- Definition, Steps, Examples (vs Dihybrid Cross)

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Monohybrid Cross

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 offspring of homozygous individuals. The hybrid produced from this cross helps in the identification of the dominant genotype in the allele. Even though monohybrid crosses are often associated with homozygous genotypes, these are also used to determine the genetic mix … Read more

Incomplete dominance vs Co-dominance- Definition, 10 Differences, Examples

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Differences between Incomplete dominance and Co-dominance

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 heterozygote. Incomplete dominance is also called partial dominance or semi-dominance as the phenotype resulting from the genotype is a blend of dominant and recessive alleles. An example of this is observed in flowers where the dominant allele is red, and … Read more

Sex-linked Inheritance

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Sex-linked Inheritance

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 a gene located on one of the sex chromosomes. The genes which occur exclusively on the X chromosome or on the analogous Z chromosome (in birds and other species) are called X- or Z -linked genes while the genes which … Read more

Twins- Types, Causes and Significance

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Twins

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 multiple births. Most commonly in the case of multiple births, the number of births is two and the individuals which are born in such a way are called twins. Twins account for over 90 per cent of multiple births. In … Read more

Characteristic of Genetic Code

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Characteristic of Genetic Code

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 of a polypeptide. Thus, the relationship between the nucleotide sequence of the mRNA and the amino acid sequence of the polypeptide is the genetic code. The nucleotide sequence is read as triplets called codons. PRINCIPLES OF THE GENETIC CODE The … Read more

Extranuclear Inheritance- Cytoplasmic Factors and Types

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Extranuclear Inheritance

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 of certain extranuclear genes or DNA molecules in the cytoplasm of many prokaryotic and eukaryotic cells. Bacterial cells such as E. coli possess a single main chromosome in the nucloid and often extra DNA elements called plasmids in the cytoplasm. … Read more

Hardy-Weinberg Equilibrium

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Hardy-Weinberg Equilibrium

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 and a German physician Weinberg (1908) independently. Both the ideas together is called as the Hardy-Weinberg law equilibrium after their names. It states that both gene frequencies and genotype frequencies will remain constant from generation to generation in an infinitely … Read more

Prokaryotic and Eukaryotic Chromosomes

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Prokaryotic and Eukaryotic Chromosomes

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 molecule. Thus a protein-coding gene is defined as a region of DNA that encodes a single polypeptide or a set of closely related polypeptides. Genes are contained in chromosomes. Chromosomes are thus structures within cells that contain hundreds to thousands … Read more

Linkage- Characteristics, Types and Significance

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Linkage

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 generation together or apart, depending on the chance alone. They assort independently according to Mendel’s law of independent assortment. But if the genes are situated in the same chromosome and are fairly close to each other, they tend to be … Read more