ICSE Biology – Chapter: Genetics (Summarised
Notes)
Gregor Johann Mendel:
Gregor Johann Mendel is called the Father of Genetics. (1822–1884).
Heredity:
Transmission of traits from one generation to the following generation. The transfer of characters
from parents to offspring is known as heredity.
Variation:
Variation in heredity is observed in sexually reproduced offspring but not in asexually produced
clones unless mutations occur.
Scientific name of Pea Plant:
Pisum sativum.
Gene:
A gene is a functional unit of heredity present on the chromosomes in the cell nucleus. It is a
segment of DNA that carries instructions for building proteins.
Chromosome:
A chromosome is a thread-like structure present in the nucleus of the cell. It appears during cell
division and carries genes.
Allele:
An allele is a different version or variant of a gene that controls a specific trait.
Phenotype:
The physical expression of a trait is called phenotype. Example: Tall pea plant.
Genotype:
The genetic make-up of an organism for a particular trait. Example: TT or Tt.
Homozygous:
When two alleles of a character are similar in a diploid condition, they are called homozygous.
Example: TT.
Heterozygous:
When two alleles of a character are different or dissimilar, they are called heterozygous. Example:
Tt.
F1 Generation:
The generation produced as a result of cross-fertilization is known as F1 generation.
F2 Generation:
The generation produced as a result of self-fertilization of the F1 generation is called F2 generation.
Notes)
Gregor Johann Mendel:
Gregor Johann Mendel is called the Father of Genetics. (1822–1884).
Heredity:
Transmission of traits from one generation to the following generation. The transfer of characters
from parents to offspring is known as heredity.
Variation:
Variation in heredity is observed in sexually reproduced offspring but not in asexually produced
clones unless mutations occur.
Scientific name of Pea Plant:
Pisum sativum.
Gene:
A gene is a functional unit of heredity present on the chromosomes in the cell nucleus. It is a
segment of DNA that carries instructions for building proteins.
Chromosome:
A chromosome is a thread-like structure present in the nucleus of the cell. It appears during cell
division and carries genes.
Allele:
An allele is a different version or variant of a gene that controls a specific trait.
Phenotype:
The physical expression of a trait is called phenotype. Example: Tall pea plant.
Genotype:
The genetic make-up of an organism for a particular trait. Example: TT or Tt.
Homozygous:
When two alleles of a character are similar in a diploid condition, they are called homozygous.
Example: TT.
Heterozygous:
When two alleles of a character are different or dissimilar, they are called heterozygous. Example:
Tt.
F1 Generation:
The generation produced as a result of cross-fertilization is known as F1 generation.
F2 Generation:
The generation produced as a result of self-fertilization of the F1 generation is called F2 generation.
