(i) Acquired traits are the characters that cannot be passed from one generation to the next generation.
(ii) Characters which are inherited by the offspring from the parents and carried from one generation to another generation are called Inherited traits.

(i) The term mutation was introduced by Hugo De Vries in 1901 when he observed phenotypic changes in the evening Primrose plant, Oenothera lamarckiana.
(ii) Mutation is an inheritable sudden change in the genetic material (DNA) of an organism.
(iii) Mutations are classified into two main types, namely chromosomal mutation and gene mutation. Chromosomal mutation: The sudden change in the structure or number of chromosomes is called chromosomal mutation. This may result in
Changes in the structure of chromosomes:
Structural changes in the chromosomes usually occurs due to errors in cell division. Changes in the number and arrangement of genes takes place as a result of deletion, duplication, inversion and translocation in chromosomes. Changes in the number of chromosomes: They involve addition or deletion in the number of chromosomes present in a cell. This is called ploidy. There are 2 types of ploidy:
Euploidy in plants and animals:
(a) Euploidy: It is the condition in which the individual bears more than the usual number of diploid (2n) chromosomes. If an individual has three haploid sets of chromosomes, the condition is called triploidy (3n). If it has four haploid sets of chromosomes. It is called Tetraploidy. Tetraploid plants are advantageous as they often result in increased fruit and flower size.
(b) Aneuploidy: It is the loss or gain of one or more chromosomes in a set. It is of 3 types:
(i) Monosomy (2n-1),
(ii) Trisomy (2n+1)
(iii) Nullisomy (2n-2). In man, Down's syndrome is one of the commonly known aneuploid condition.
Gene or point mutation:
(i) Gene mutation is the changes occurring in nucleotide sequence of a gene.
(ii) It involves substitution, deletion, insertion or inversion of a single or more than one nitrogenous base.
(iii) Gene alteration results in abnormal protein formation in an organism.

(i) DNA molecule produces exact copies of its own structure during replication process.
(ii) The two strands of a DNA molecule have complementary base pairs. The nucleotides of each strand provide the information needed to produce its new strand.
Origin of replication: The specific points on the DNA, where the replication begins. It is the site of origin of replication. The two strands open and separate at this point forming the replication fork.
Unwinding of DNA molecule:
(i) The enzyme called helicase, bind to the origin of replication site.
(ii) They separate the two strands of the DNA. The enzyme called topoisomerase seperates the double helix above the replication fork and removes the twists formed during the unwinding process.
(iii) Each of the separated DNA strands function as template.
Formation of RNA primer: An RNA primer is a short segment of RNA nucleotides. The primer is synthesized by the DNA template close to the origin of replication.
Synthesis of new complimentary strand from the parent strand :
(i) After the formation of RNA primer, nucleotides are added with the help of an enzyme DNA polymerase and new complimentary strand of DNA is formed from each of the parent strand. The synthesis is unidirectional.
(ii) In one strand the daughter strand is synthesized as a continuous strand which is called leading strand.
(iii) In the order stand, short segment of DNA are synthesized. This strand is called lagging strand.
(iv) The short segments of DNA are called Okazaki fragments. The fragments are joined together by the enzyme DNA ligase.
(v) The replication stops when the replication fork of the two sides meet at a site called terminus which is situated opposite to origin of replication site

Based on the position of centromere, the chromosomes are classified as Telocentric, Acrocentric, Submetacentric andMetacentric.
(i) Telocentric - The centromere is found on the proximal end. They are rod shaped chromosomes.
(ii) Acrocentric - The centromere is found at the one end with a short arm and long arm. They are also rod - shaped chromosomes.
(iii) Submetacentric - The centromere is found near the centre of the chromosome. Thus forming two unequal arms. They are J

(iv) Metacentric - The centromere occurs in the centre of the chromosome and form two equal arms. They are V shaped chromosomes.

(i) In the DNA replication after the formation of RNA primer two strands are formed.
(ii) In one strand short segments of DNA are synthesised.
(iii) This strand is called lagging strand. The short segments of DNA are called okazaki fragments.

(i) Human beings have 23 pairs of chromosomes out of which 22 pairs are autosomes and one pair (23^rd pair) is the sex chromosome.
(ii) The female gametes or the eggs formed are similar in their chromosome type (22+XX).
(ii) Therefore, human females are homogametic.

(iv) The male gametes or sperms produced are of two types.
(v) They are produced in equal proportions.
(vi) The sperm bearing (22+X) chromosomes and the sperm bearing (22+Y) chromosomes.
(vii) The human males are called heterogametic.
(v) It is a chance of probability as to which category of sperm fuses with the egg.
(vi) If the egg (X) is fused by the X-bearing sperm an XX individual (female) is produced.
(vii) If the egg (X) is fused by the Y-bearing sperm an XY individual (male) is produced.
(viii) The sperm, produced by the father, determines the sex of the child. The mother is not responsible in determining the sex of the child.
(ix) Now let's see how the chromosomes take part in this formation.
(x) Fertilization of the egg (22+X) with a sperm (22+X) will produce a female child (44+XX) while fertilization of the egg (22+X) with a sperm (22+Y) will give rise to a male child (44+XY).

(i) Dihybrid cross involves the inheritance of two pairs of contrasting characteristics (or contrasting traits) at the same time.
(ii) The two pairs of contrasting characteristics chosen by Mendel were shape and colour of seeds: round-yellow seeds and wrinkled-green seeds.
(iii) Mendel crossed pea plants having round - yellow seeds with pea plants having wrinkled green seeds.
Mendel made the following observations:
(i) Mendel first crossed pure breeding pea plants having round-yellow seeds with pure breeding pea plants having wrinkled green seeds and found that only round yellow seeds were produced in the first generation (F₁).
(ii) No wrinkled-green seeds were obtained in the F₁ generation.
(iii) From this it was concluded that round shape and yellow colour of the seeds were dominant traits over the wrinkled shape and green color of the seeds.
(iv) When the hybrids of F₁ generation pea plants having round-yellow seeds were cross-breed by self pollination, then four types of seeds having different combinations of shape and colour were obtained in second generation or F₂ generation.
(v) They were round-yellow, round-green, wrinkled yellow and wrinkled-green seeds.
(vi) The ratio of each phenotype (or appearance) of seeds in the F₂ generation is 9:3:3:1. This is known as the Dihybrid ratio.
(vii) From the above results it can be concluded that the factors for each character or trait remain independent and maintain their identity in the gametes.
(viii) The factors are independent to each other and pass to the offsprings (through gametes).

Results of a Dihybrid Cross:
(i) Mendel got the following results from his dihybrid cross.
Four Types of Plants:
(i) A dihybrid cross produced four types of F₂ offsprings in the ratio of 9 with two dominant traits, 3 with one dominant trait and one recessive trait, 3 with another dominant trait and
another recessive trait and 1 with two recessive traits.
New Combination:
(i) Two new combinations of traits with round green and wrinkled yellow had appeared in the dihybrid cross (F₂ generation).

Kavitha's family members' statement is false, because the sex is determined by male.
In human being female gametes form the chromosome type 22+XX. But in male gametes two types of chromosomes are formed. One is (22+X) another one is (22+Y).
(i) If a female gametes are (22+X) fuses with a male gamete (22+X) than its forms a female child.
(ii) If a female gamete (22+X) is fuses with the male gamete (22+Y) than it forms a male child.
(iii) The sex is determined by the male gamete.

a) The F₁ generation plants are tall.
b) In the F₁ generation there were 3 tall plants and a dwarf plant. The ratio is 3 : 1.
c) The dwarf plants were missing in F₁ generation but reappeared in F₂ generation.

(i) Flowers of the garden pea are bisexual and self-pollinated.
(ii) During hybridization experiment, Mendal simply cut off anther in bud (Emasculation) and did the cross pollination of selected plant's pollen on the stigma of the flower.
(iii) So self pollination will be avoided.
(iv) And there by he followed the effects of crossing for several generation.