Test: Inheritance of One Gene & Two Genes (November 27) - NEET MCQ

Emasculation is the process of removal of anthers. This is carried out to carry out pollination in a controlled manner and avoid self-pollination.

F1 progeny refers to the first generation of offsprings. This is also termed as the first Filial generation, thereby stating their filial relationship with the true-breeding plants.

Violet is the dominant factor over white in pea flowers. Hence violet can express even in the presence of white. The cross of violet true-breeding and white true-breeding pea plants will produce all heterozygous offsprings. Thus, all of them will have violet flowers.

A dominant factor masks the expression of its recessive counterpart. Thus, it can express in both homozygous and heterozygous states.

Based on his studies on pea plants, he observed that the parental recessive traits were observed again only in the F2 progeny without any form of blending in F1 generation. This points out that the factors segregate or separate during the process of meiosis.

In a self-cross of heterozygous violet-flowered pea plants (Vv), the Punnett square for the flower color gene would yield the following genotypic and phenotypic ratios:

Genotypic Ratio: 25% VV (violet), 50% Vv (violet, but carrying the white allele), 25% vv (white)
Phenotypic Ratio: 75% violet and 25% white

This means that 75% of the offspring would have violet flowers, and 25% would have white flowers. Therefore, the correct answer is option D, "75% violet and 25% white.

The F2 progeny has both dwarf and tall plants. 25% of them are homozygous tall, 50% are heterozygous tall, and 25% are homozygous dwarf. Dwarfness is a recessive trait and thus cannot be expressed in the heterozygous state.

Complete linkage is defined as the state in which two loci are so close together that alleles of these loci are virtually never separated by crossing over.  In the case of male Drosophila there is a complete absence of recombinant types due to the absence of crossing over. This means that all of the genes that start out on a single chromosome, will end up on that same chromosome in their original configuration.
So, the correct answer is 'Male Drosophila'.

XX-XO type or Protenor type : Mc clung in male squash bug (Anasa) observed 10 pairs of chromosomes and an unpaired chromosome. Their females have eleven pairs of chromosomes (22). Thus all the eggs carry a set of eleven chromosomes but the sperm are of the two types: fifty percent with eleven chromosomes and the other fifty percent with ten chromosomes. The accessory chromosome was X-chromosomes. Fertilization of an egg by a sperm carrying eleven chromosomes results in a female, while its fertilization by a sperm with ten chromosomes produces male. It is said to be evolved by the loss of Y-chromosome. e.g., Grasshopper and plant kingdom in Dioscorea sinuta and Vallisneria spiralis.

Chromosomal crossover (or crossing over) is an exchange of genetic material between homologous chromosomes. It is one of the final phases of genetic recombination, which occurs during prophase I of meiosis (pachytene) in a process called synapsis. Synapsis begins before the synaptonemal complex develops, and is not completed until near the end of prophase I. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome.