NEET Practice Questions (MCQs) with Answers & Solutions

In ABO blood groups system, inheritance of grouping is controlled by a single autosomal gene on chromosome 9 with three major alleles A, B and O ( I^A, I^B and i^O). The ABO blood group system has at least 6 genotypes. on the basis of presence or absence of antigens and antibodies, four blood groups (phenotypes) have been differentiated — A, B, AB and O blood groups. 

Recombination is a rearrangement of genes during meiosis so that a gamete contains a haploid genotype with a new gene combination. Morgan and his group found that when genes were grouped on the same chromosome, some genes were very tightly linked (showed very low recombination), while others were loosely linked (showed higher recombination).

Inheritance of skin colour in humans is the result of polygenic inheritance or multiple factor inheritance. The inheritance of human skin colour was studied by C.B. Davenport in 1913.

The more maternal influence can be expected in the cytoplasmic inheritance (i.e., the inheritance of genes contained in the cytoplasm of a cell, rather than the nucleus). The resason is that the female reproductive cell or the egg has a large amount of cytoplasm containing many such organelles which ciontain their own genes and can reproduce independently (e.g., mitochondra and chloroplast) and whcih are consequently incorporated into the cytoplasm of all the cells of the embryo. The male reproductive cells (sperm or pollen) consist almost solely of a nucleus. Cytoplasmic organelles are thus, not inherited from the male parent. 

This is why, the cytoplasmic inheritance is also called as maternal inheritance.

Genes located on Y-chromosome are called Y-genes and their inheritance is called Y-linked inheritance. This carries the paternal influences.

A gene located in the X-chromosome is said to be X-linked and its inheritance is called X-linked inheritance. In this, a male transmits his X-chromosome only to his daughters while a female transmits one of her X-chromosomes to the offspring of both sexes. 

The types of gametes produced by a plant depend upon the number of heterozygous pair.

Number of types f gametes = Zⁿ

n = nymber of heterozygous pair

2¹ = 2

The gametes are — ABC and AbC.

Polygenic inheretance  involves the determination of a particular phenotypic characteristic by many genes, called polygenes (i.e., the group of genes influencing a quantitative characteristic), each having a small effect individually. 

The characteristics controlled in this way show continuous variation and are called polygenic characters e.g., height and skin color in humans.

The polygenic inheritance is called multifactorial inheritance or quantitative inheritance. 

the pink flower colour in Mirabilis jalapa is an example of incomplete dominance which production of male honey bee is an example of parthenogenesis.

The test cross involves the crossing of F₁ hybrid with a double recessive genotypic parent. By test cross, the heterozygocity and homozygocity of the organism can be tested. 

Thus, the offispring will be 100% dominant, if the individual which crossed with recessive parent, i.e., (tt) was homozygous dominant and ratio will be 50% dominant and 50% recessive if the individual was heterozygous dominant. in dihybrid test cross, ratio will be 1:1:1:1.

Trait is any detectable phenotypic variation of a particular inherited character.

Cri du chat is a rare syndrome (1 in 50, 000 live births) caused by a deletion on the short arm of chromosome 5, is a rare genetic disorder due to a missing portion of chromosome 5. It was first described by Lejeune in 1963. The name of this syndrome is French for "cry of the cat," referring to the distictive cry of children with this disorder. The cry is caused by abnormal larynx development, which becomes normal within larynx development, which becomes normal within a few weeks of birth. Infants with cri du chat have low birth weight and may have respioratory problems. 

Recombination is the natural process of breaking and rejoining DNA strands to produce new combination of genes and, thus, generate genetic variation. This is the phenomenon which occurs during meiosis I.