Principles of Inheritance & Variation Test - 10

A person with unknown blood group under ABO grouping should be given Type O blood group as O is universal donor and can be transfused to any person.

Blood type AB in humans is an example of co-dominance, where both A and B alleles express themselves equally in the phenotype. Individuals with AB blood type have both A and B antigens on the surface of their red blood cells. This contrasts with incomplete dominance, where the heterozygote expresses a blend of the two parental phenotypes.

• The process of segregation that occurs during meiosis is a random process.
• Thus the gametes will have 50% of each allele.
• Hence Vv heterozygous plant would produce 50% V and 50% v containing gametes.

According to question, tallness (T) is dominant over dwarfism (t) and red colour (R) is dominant over white (r) fruit colour.

Parent Generation; P₁ : RRTt  x  rrtt

F₁ generation :

Phenotypic ratio = 1  (tall plant, red fruit)     
: 1 (dwarf plant, red fruit)
; thus, percent of tall plant with red fruit is 50%.

AB blood group of mother have two alleles IA and IB. The heterozygous B blood group of father has alleles IB and i. The possible outcome are IA IB,IAi,IBIB and IBi. That form AB, A, B and B blood group respectively.

An organism with lethal mutation may not even develop beyond zygote stage due to change in gene but all kinds of mutations are not lethal. Mutation is main source of variation essential for evolution.

Deviation from Medelism ’s occurs due to co-dominance, multiple alleles, incomplete dominance in which single gene is not completely dominant over the other to produce dominant trait.

T.H.Morgan worked on the tiny fruit fly called Drosophila melanogaster. This tiny fly shows variation in eye colour and can be easily crossed with other to show the flow trait.

Chromosome theory of XY sex determination was proposed by Wilson and Stevens.

Crossing over occurs at four strand stage of panchytene of meiosis-I. Each homologous chromosome has two stands. Exchange of gene occurs during this period.

In birds male contain a pair of Z chromosome as sex chromosome besides autosomes while female contain one Z and one W chromosome.

Linkage is the physical association of two genes present on same chromosome. Genes located close to each other have high linkage percentage.

Male birds bears ZZ sex chromosome as sex determination is ZO type, in which ZZ is male and ZO is female.

Two genes p and q showing 1.3% of recombination while other two genes x and y show 37.2 percent of recombination. p and q genes are present close to each other as they show less recombination percentage.

In human beings, 23 pairs of chromosomes are present in diploid cells.
Twenty two pairs of chromosomes are equal in male and female but a pair sex chromosome is different in them. Male contain XY and female contain XX sex chromosome.