NEET Practice Questions (MCQs) with Answers & Solutions

After entering one of the synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid. One of the male gametes moves towards the egg cell and fuses with its nucleus thus resulting in the formation of a diploid cell, the zygote. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus (PEN).

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The pure strain is homozygous.

Women have 2 X chromosomes, one comes father and the other from her mother. 

Translocation is the process causing a gene to move from one linkage group to another. It is the separation of a chromosome segment and its union to a non-homologous chromosome. It is of two types - Simple and  reciprocal.

In simple translocation one chromosome shows deletion of deficiency while a non-homologous chromosome comes to have an additional segment. In reciprocal translocation two non-homologous chromosomes exchange segments between themselves to create new linkage groups in both the chromosomes. 

Hence, option is correct.

(c) A true breeding plant (pureline) has homozygous genes for a character (e.g., TT for tall or tt for dwarf). It always produces offsprings which are true (pure) for its characters.

The term linkage was coined by TH Morgan. He carried out several dihybrid crosses in Drosophila to study genes that were sex-linked. He described the physical association of genes on a chromosome.

(b) The movement of a gene from one linkage group to another is called translocation. It is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes.

(c) Mutiple alleles is a condition where a gene exist in more than two allelic forms that are present on the same locus of the chromosome. For eg : ABO system in humans.

The law of dominance does not occur universally. After Mendel several cases were recorded by scientists, where a clear deviation from law of dominance was seen in the form of incomplete dominance or Blending inheritance and Co-dominance. 

Where F₁ generation hybrids exhibited a mixture or blending of character of two parents, the case is considered as that of incomplete dominance blending inheritance. It is simply means that two genes of allelomorphic pair are not related as dominant or recessive, but each of them expresses itself partially. In the case of 4 o'clock plant, when plants with red flowers are crossed with plants having white flower, the F₁ hybrids bear pink flowe. When these pink flowers are self pollinated, they develop red, pink and white flowers in the ratio of 1 : 2 : 1 respectively. 

In genetics, a test cross, first introduced by Gregor Mendel, is used to determine if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait. More simply, test cross determines the genotype of an individual with a dominant phenotype. In some sources, the test cross is defined as being a type of back cross between the recessive homozygote and F₁ generation.