Visitors Online: 2585 | Thursday 18th December 2014
CBSE Biology Subject Notes
CBSE Guess > eBooks > Class X > Heredity and Evolution By Mr. Ajay Kumar
HEREDITY AND EVOLUTION
HEREDITY : - The transmission of characters from the parents to their offspring’s is called heredity.
VARIATION : -
The differences in the characters among the individuals of a species in called variation. The great advantage of variations to a species is that it increases the chance of its survival in a changing environment.
CHROMOSOME : -
Chromosome is a thread-like structure in the nucleus of a cell formed of DNA which carries the gene.
GENE : -
A gene is a unit of DNA on a chromosome which governs the synthesis of one protein that controls a specific characteristic of an organism. Genes are actually units of heredity which transfer characteristics from parents of their offspring’s during reproduction.
DOMINANT GENE : -
The gene which decides the appearance of an organism even in the presence of an alternative gene is known as a dominant gene. It dominated the recessive gene for the same characteristic on the other chromosome of the pair.
RECESSIVE GENE : -
The gene which can decide the appearance of an organism only in the presence of another identical gene is called a recessive gene.
GENOTYPE : -
Genotype is the description of genes present in an organism and a pair of letters TT, Tt or tt.
PHENOTYPE : -
The characteristic which is visible in an organism is called its phenotype and ‘tall’ or ‘dwarf‘.
FIRST FILIAL GENERATION OR F1 GENERATION : -
When two parents to produce progeny, then their progeny is called first filial generation or F1 generation.
SECOND FILIAL GENERATION OR F2 GENERATION : - When the first generation progeny cross among themselves to produce second progeny, then this progeny is called second filial generation or F2 generation.
HYBRID : - A new form of plant resulting from a cross of different varieties of a plant is known as a hybrid.
Submitted By Mr. Ajay Kumar
Email Id : email@example.com