Biology [2 Mark Question Answer]

Mendel's work did not receive much notice till 1900. Then three scientists: Hugo de Vries, Carl Correns and Erich von Tschermak working independently rediscovered his work and brought Mendel's experiment to limelight.

phenotype ratio of :
(a) TT x Tt - All progeny plants will be tall
(b) tt x TT - All the progeny plants will be tall
(c) TTrr x ttRR = All progeny will be tall having round seeds
(d) TtRr x TtRr = 9 : 3 : 3 : 1 (9 - Tall and Round seeds; 3 - Tall and wrinkled seeds; 3 - Dwarf and Round seeds; 1 - Dwarf and wrinkled seeds.)

Genotype - TtRr - All Hybrid
Phenotype - All tall and round seeds

Identical twins - A single fertilized egg or Zygote splits into two parts after conception, resulting in the development of two individual embryos which later develop into indentical twins.

Laws of Inheritance - Gregor Johann Mendel performed experiments with different varieties of garden pea and then formulated a few laws to study the inheritance of characters on living organisms.

A man can never transfer a sex-linked gene directly to his son because the son inherits only the Y chromosome from his father and the sex linked diseases are present on the X chromosome.

Haemophilia is X-linked inherited disease in which the diseased person is unable to synthesize a normal blood protein called Antihaemophilic globulin that helps in clotting. Haemophilia is also called Bleeder's disease as the haemophilic person bleeds for a long time even from a minor cut.

The sex of the zygote is determined by the sperm which fertilizes the ovum. If an X bearing sperm fuses with an ovum in man, the offspring would be female and if a Y chromosome bearing sperm fuses with an ovum the offspring will be a boy.

Mendel's laws are:
(a) Law of Dominance
(b) Law of Segregation
(c) Law of Independent Assortment

Gregor Johann Mendel was a biologist who carried out experiments on garden pea and derived a few fundamental principles in genetics. He is called the 'Father of Genetics'.

The law of segregation explains that the characteristics of an organism are determined by internal alleles that occur in pairs. These allele pairs separate during meiosis in gamete formation and the pair gets restored upon random fusion in zygote.