Genetics and Plant Breeding

Incomplete dominance occurs when the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes. Crossing red and white cattle to produce roan (a mix of red and white hairs) is a classic example of co-dominance, but in many textbooks, this specific scenario is often used to illustrate incomplete dominance or co-dominance depending on the definition of the trait.

Mendel crossed two parent plants having contrasting characters. He found that in the first filial generation, F1 generation, the dominant of the two expressed while the recessive is suppressed. Apart from this,  When the f1 generation is self crossed, in the F2 generation, these recessive characters appear again. Therefore, it is not that they have disappeared. 

Linkage is the tendency of two or more genes to inherit together as a pair and not to sort out independently.
Thus, linkage is not applicable according to Mendelian principles.
Linkgae is strictly against Law of independent assortment where Mendel explains that the characters are sorted out independently while forming gametes.

Meiosis is otherwise called as Reductional division where the ploidy level of the organism is halved. Meiosis occurs in sex cells where Law of Independent assortment is well applicable. Because during meiosis, the hereditary units are inherited independently and segregated in chromosomes. One allele of a trait segregates and moves to the chromosomes such that the offspring can acquire characters from any one parent. Thus the law of Segregation also is proved well by the process of Meiosis. The expression of phenotype very well depends on Mendel's law of dominance. The dominant character is expressed in both homozygous and heterozygous forms. Whereas recessive characters are expressed only in homozygous forms.

 According to the law of seggregation  alleles of a trait that remain together in an individual do not mix but rather keep their identity intact. They separate during gamete formation and get randomly distributed only to get paired again in the offspring’s as per the principle of probability. This results in a phenotypic trait in the 3:1 ratio in the F2 generation i.e when a heterozygous plant is crosssed. So, the correct answer is 'Law of segregation'.

• In the population of 400 individuals if 40% is recessive allele and 60% will be dominant (144).

Incomplete dominance F2 phenotypic ratio is 1:2:1, and the genotypic ratio of a monohybrid F2 is also 1:2:1.

Law of segregation or law of purity of gametes holds in all situations whereas Law of independent assortment is violated in case of linkage and law of dominance is violated when codominance and incomplete dominance takes place.

Mendel's law of heredity explains that there is some factor that inherits the characters from one generation to next. To explain this  he gave 3 laws which are :
1. Law of dominance
2. Law of purity of gametes (Principle of segregation)
3. Law of independent assortment

Dihybrid cross proves the law of independent assortment. Mendel found that each pair of alleles segregates independently of the other pairs of alleles during gamete formation. This is known as Law of independent assortment. Dihybrid cross - cross between two parents that differ by two pairs of alleles (AABB X aabb). The formation of gametes is an application of this law.

Principle of segregation: According to the principle, for any particular trait, the pair of alleles of each parent separate and only one allele passes from each parent on to an offspring. Which allele in a parent's pair of alleles is inherited is a matter of chance. We now know that this segregation of alleles occurs during the process of sex cell formation.

 1) J.Mendel's carried out a various experiment on garden pea in a scientific manner and gave principles which are now known Mendel's law of inheritance. The principle of segregation is also called as the law of purity of gametes is first law of Mendle. A gamete may carry either the dominant or the recessive factor but not both as we find in F11 individuals. The gametes which are formed are always pure for a particular character. This is why it is called either as the principle of segregation or law of purity of gametes. 2) As per the law of dominance, dominant characters will express in both homozygous and heterozygous conditions. Whereas, recessive characters are the characters which can express only when it is present in homozygous condition. F1generation thus, shows the mixing of characters and will not inherit as such without mixing. 3) According to Mendel's law of independent assortment, during the inheritance of two or more characters, the assortment of individual traits takes place independently during gamete formation. Thus each allele of a pair segregates independently and each gamete formed contains one allele of that trait. Thus, the correct answer is option C.

The law of segregation states that every individual contains a pair of alleles for each particular trait which segregate or separate during cell division for any particular trait and that each parent passes a randomly selected copy called as allele to its offspring. The offspring then receives its own pair of alleles of the gene for that trait by inheriting sets of homologous chromosomes from the parent organisms. Interactions between alleles at a single locus are termed dominance and these influence how the offspring expresses that trait. The law states that when any individuals produces gametes, the copies of a gene separate so that each gamete receives only one copy allele. A gamete will receive one allele or the other.

According to Mendel's law, the alleles separate and segregate into gametes during meiosis. 

Mendel's law of segregation : Allele pairs separate or segregate during gamete formation and randomly unite at fertilization. There are four main concepts related to this principle. They are as follows: