Genetics & Modern Science

Genetics & Modern Science

Genetics and Heredity

Heredity

• Transmission of character from one generation to the next generation is called heredity.

Genetics

• The process of transfer of hereditary character from generation to generation is called genetics.

• The name 'genetics' was first coined by W. Bateson in 1905.

• Johannes first used the name Gene in 1909.

Father of Genetics

• Gregor Johan Mendel was the first who gave the idea of heredity based on his experiment in 1822–1884.

• He is also known as the father of genetics.

Mendel’s Experiments

Choice of Plant

• Mendel chose pea plants for his experiment.

Monohybrid Cross

• Mendel made a cross between two pure plants having contrasting characters for a single trait, called a monohybrid cross, i.e., a tall and dwarf plant for height.

Dihybrid Cross

• Mendel made a cross between two pure plants having a pair of contrasting characters, i.e., colour and shape of seed, called a dihybrid cross.

He made a cross between a plant having round seeds with yellow colour and wrinkled seeds with green colour.

Mendel’s Laws of Inheritance

1. Law of Paired Unit

• Mendel proposed that when two dissimilar unit factors are present in an individual, only one is able to express.

• One that expresses itself is the dominant unit factor, and the other, which fails to express, is the recessive unit factor.

  • For example, tallness is dominant over dwarfness.

2. Law of Dominance

• Offspring of crossbred parents only show dominant characters in the F1 generation.

3. Law of Segregation

• In the F2 generation, both the characters which are governed by genes are separated.

4. Law of Independent Assortment

• During dihybrid and trihybrid crosses, two or three pairs of characters are taken.

• These characters segregate separately without depending on each other in the F2 generation.

Terms Related to Genetics

Linkage

• Linkage is an exception to Mendel's law. When two different genes are present on the same chromosome, they express themselves together instead of independently.

• This phenomenon is known as linkage.

• The word 'linkage' was first coined by Morgan (1910).

Mutation

• A sudden change in the gene which is heritable from one generation to another.

• The term 'mutation' was first coined by Hugo De Vries.

Variation

• When characters are transmitted from one generation to the next generation, there is some change.

• Change in characters by recombination of genes in offspring, so they look different from their parents.

• This phenomenon is known as variation.

Chromosomal Aberrations

• Any change in chromosomal structure is known as chromosomal aberration.

Cloning

• It is a process of producing an identical organism from a single cell having the same genetic character as its mother.

  • Ex.: Sheep Dolly was produced from a single cell.

• Dolly was assigned to the world’s first clone of an adult animal by British scientists.

Totipotency

• It is the potential ability of a plant cell to grow into a complete plant.

Pluripotency

• It is the potential ability of a cell to develop into any kind of cell in an animal body.

Genetically Modified Organism (GMO)

• Manipulation of a gene by cutting or joining the segment of DNA to get desired varieties of organisms is called genetically modified organism.

• This is also known as genetic engineering.

Autosomes

• Chromosomes found in cells which are responsible for characters other than sex are called autosomes.

Sex Chromosome

• The pair of chromosomes which determine the sex of an organism are called sex chromosomes.

• Humans have 23 pairs of chromosomes, in which 22 pairs are autosomes and one pair are sex chromosomes.

Genome

• All genes present in a haploid cell are called a genome.

Plasmagen

• Genes which are found in organelles of cytoplasm are called plasmagen.

Cistron

• The functional unit of a gene is called a cistron.

Mutton

• Unit of gene responsible for mutation.

Recon

• A unit of a gene takes part in recombination.

Additional Notes in Genetics

• S. Benzer (1962) had given the modern definition of gene.

• The gene which exhibits multiple effects is called pleiotropic.

• When one gene pair hides the effect of another unit, it is called epistasis.

• DNA fingerprinting is a technique used for the detection of disputed parentage.

• Reverse transcription was discovered by Temin & Baltimore.

• Targeted drug delivery and gene therapy are made possible by the use of nanotechnology in the health sector.

• Bt brinjal is a genetically engineered form of brinjal developed to make it pest-resistant.

• In recent developments of science, a functional chromosome cannot be created by joining DNA segments from different species.

• Genetic predisposition of some people is the reason for multi-drug resistance.

• Cas I protein is a molecular scissors used in targeted gene editing.

• In normal cells, the process of the flow of genetic information from DNA to RNA is called transcription.

• In eukaryotic cells, genes present in the cytoplasm are found in the mitochondria and inherited via egg cytoplasm.

• Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilisation of the egg.

• A child inherits mitochondrial diseases entirely from the mother and not from the father.

• Extranuclear genes occur in mitochondria and are inherited by the female.

• The chromosomal theory of inheritance was given by Sutton & Boveri.