Genetics and Plant Breeding

 In experiments performed by Mendel all the genes showed independent assortment, in which genes separate from each other independently and there was no sign of any linked gene so he could not explain the concept of linkage, because he never observed it .

Law of segregation states that alleles for genes segregate from each other whether it is for tall (TT) or dwarf (tt) so that the gamete carries one allele for each gene, whereas law of dominance states that the phenotype which is expressed is the dominant character and other is recessive, since there are both tall & dwarf plants, this means that both characters are expressed . 

Law of segregation and Law of independent assortment are based on the mechanism of meiosis, because these principles show segregation of characters and independent movement of characters.

So, the correct option is ‘Meiosis’.

• Mendelian factors or genes, as well as chromosomes, are present in pairs.
• According to this Mendelian concept, inheritance of a trait depends on the passing-on of units. 
• For any given trait, an individual inherits one gene from each parent so that the individual has a pairing of two genes.

• The trait is a distinguishable feature of a character and its detectable variant. For example, tallness and dwarfness. 
• The hybrid plant possesses a heterozygous condition in which genotype have both contrasting alleles such as Tt in the hybrid plant. T represents tallness and t represents dwarfness.
•  Dominant character tallness (T) can be expressed in both conditions such as homozygous (TT) and heterozygous condition (Tt) but recessive character dwarfness (t) can be expressed only in homozygous (tt) condition and thus unable to express in hybrid plants.

• Segregation literally means separation. In Mendelian genetics, in a given plant or animal each character is governed by two alleles, one coming from the father and one coming from the mother.
•  At the time of gamete formation both the alleles, of each gene, separate from each other and go to separate gametes. 
• Thus, each gamete will be having only one allele from each pair of the allele, e.g., for tallness if we denote two alleles in a plant as Tt then that plant can form two possible gametes one having T and the other having t allele.

• Segregation means separation. In classical Mendelian genetics, it is assumed that each individual has two alleles which code for each character. 
• One allele comes from the father and the other from the mother. These two alleles separate from each other during gamete formation. 
• Thus, each gamete contributes a single allele for each character during zygote formation.

Mendel's law of genetics is applicable only in plants which reproduce sexually. In Mendelian genetics he explains about the independent assortment which results in the formation of gametes which has the contrasting characters from both male and female parents. It will be expressed according to its zygosity and dominant traits. if the recessive trait is present in its homozygous form, the character will be expressed. At the same time, dominant character will be expressed in both homozygous and heterozgous forms. Pisum sativum which Mendel chose was a sexually reproducing plant.

Pea plant has 2n= 14. Mendel chose 7 characters the genes for which are present on 7 different chromosomes. The presence of different chromosomes allowed genes for two traits to assort independently during dihybrid cross and recombinant progeny, as well as parental progeny, is produced. If he had chosen eight characters, genes for any two characters must be present on the same chromosome and would exhibit linkage and the law of independent assortment is violated. Law of dominance explains the appearance of a dominant trait by heterozygous genotype and law of segregation tells about segregation of alleles of heterozygous genotype during gamete formation. Law of purity tells about the presence of a single allele of a gene in gametes. Thus, the correct answer is option C.

• According to the law of dominance, a trait is represented by two contrasting factors of a gene in a heterozygous individual; only dominant trait is expressed, irrespective of the presence of both factors, in a heterozygous individual.
•  It does not tell about the reappearance of the missing trait in $F _2$ generation. The law of segregation states that the two factors for a trait, present together in a heterozygous individual, do not get mixed and are separated during gametogenesis. 
• Thus each gamete receives one allele for a trait and two types of gametes are formed; 50% gametes carry factor for dominance and 50% carry the recessive factor. Random fusion of these gametes leads to the presence of both recessive and dominant individuals in $F _2$ generation. 
• Law of independent assortment tells about segregation and distribution of factors governing two different traits; not about segregation of factors of one trait. Incomplete dominance is the condition when none of the factors of a gene is dominant and the phenotype of a heterozygous dominant individual is a blend of dominant and recessive traits. 
• It affects the phenotype of $F _1$ individuals, not that of $F _2$. Thus, the correct answer is option B.

Gregor Johann Mendel, an Austrian Monk, discovered the principles of heredity through the experiments on the pea plant. Mendel conducted hybridization experiments on garden peas for seven years and proposed the laws of inheritance in living organisms. They are the Law of dominance, Law of segregation, Law of Independent assortment.

So, the correct option is ‘Three’.

The blending theory state that the inheritance of traits from two parents produces offspring with characteristics that are intermediate between those of the parents.

The incorrect pair here is the contrasting feature of the pod shape is "Elongated/constricted" which should be smooth/constricted in reality.