NCERT Solutions for Class 12 Biology Chapter 5
NCERT Solutions for Class 12 Biology Chapter 5 Principle of Inheritance and Variation to Study Online or Free download in PDF form for the academic session 2020-21 for all boards who are using NCERT Books 2020-21.NCERT Books 2020-21 are based on latest CBSE Syllabus 2020-2021 is given to download for all the subjects. Join the Discussion Forum and discussion your doubts related to education.
NCERT Solutions for Class 12 Biology Chapter 5
|Chapter 5:||Principle of Inheritance and Variation|
Class 12 Biology Chapter 5 Solutions in English
What do you understand by Law of Independent Assortment?
In the inheritance of two pairs of contrasting characters (dihybrid cross) the factors of each pair of characters segregate independently of the factors of the other pair of characters.
What is Chromosomal Theory of Inheritance?
Chromosomal Theory of Inheritance: Proposed by Sutton and Boveri. The pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried. They united the knowledge of segregation with Mendelian principles.
What is meant by Pleiotropy?
The ability of a gene to have multiple phenotypic effects because it influences a number of characters simultaneously is known as pleiotropy. The gene having a multiple phenotypic effect because of its ability to control expression of a number of characters is called pleiotropic gene. E.g. in Garden Pea, the gene which controls the flower colour also controls the colour of seed-coat and presence of red spot in the leaf axis.
Important Terms related to Chapter 5
1. Phenotype: The observable or external characteristics of an organism.
2. Genotype: The genetic constitution of an organism.
3. Aneuploidy: The phenomenon of gain or loss of one or more chromosome(s), that results due to failure of separation of homologous pair of chromosomes during meiosis.
4. Trisomy: The condition in which a particular chromosome is present in three copies in a diploid cell/nucleus.
5. Male heterogamety: When male produces two different types of gametes/sperms e.g., In human beings X and Y.
6. Female Heterogamety: When female produces two different types of gametes/ova, e.g., female bird produces Z and W gametes.
Law of Dominance
When two individuals of a species differing in a pair of contrasting characters/traits are crossed, the trait that appears in the F1 generation is dominant and the alternate from that remain hidden, is called recessive.
Law of Segregation (law of purity of gametes): The members of allelic pair that remained together in the parent, segregate/separate during gamete formation and only one of the factors enters a gamete.
Important Questions on 12th Biology Chapter 5
He selected a pea plant because of the following features.
Peas have many visible contrasting characters such as tall/dwarf plants, round/wrinkled seeds, green/yellow pod, purple/white flowers, etc.
Peas have bisexual flowers and therefore undergo self-pollination easily. Thus, pea plants produce offsprings with same traits generation after generation.
In pea plants, cross pollination can be easily achieved by emasculation in which the stamen of the flower is removed without affecting the pistil.
Pea plants have a short life span and produce many seeds in one generation.
Co-dominance is the phenomenon in which both the alleles of a contrasting character are expressed in heterozygous condition. Both the alleles of a gene are equally dominant. ABO blood group in human beings is an example of co-dominance. The blood group character is controlled by three sets of alleles, namely, IA, IB, and i. The alleles, IA and IB, are equally dominant and are said to be co-dominant as they are expressed in AB blood group. Both these alleles do not interfere with the expression of each other and produce their respective antigens. Hence, AB blood group is an example of co-dominance.
It is an autosomal linked recessive disorder, which is caused by point mutation in the beta-globin chain of haemoglobin pigment of the blood. The disease is characterized by sickle shaped red blood cells, which are formed due to the mutant haemoglobin molecule. The disease is controlled by HbA and HbS allele. The homozygous individuals with genotype, HbS HbS, show the symptoms of this disease while the heterozygous individuals with genotype, HbA HbS, are not affected. However, they act as carriers of the disease.
Rapid heart rate, breathlessness, delayed growth and puberty, jaundice, weakness, fever, excessive thirst, chest pain, and decreased fertility are the major symptoms of sickle cell anaemia disease.