CBSE Questions for Class 12 Medical Biology Principles Of Inheritance And Variation Quiz 15 - MCQExams.com

• In given pedigree, unaffected parents have affected offspring which means that either one or both parents are a carrier.
• It also shows recessive nature of the trait; if the trait was dominant it would have been expressed by heterozygous individuals as well. But heterozygous parents are serving as carrier only.
• In offspring, both sons and daughters are not equally; sons are affected. This means disease is not autosomal; if it was autosomal, both sons and daughters of carrier parents would be equally affected.
• The affected son of first offspring generation and normal female have all normal children.
• This means the trait is X linked recessive trait and affected father has passed the affected X chromosome to daughter. 
• The daughter is carrier only because mother is normal. Likewise, normal females of first offspring generation and normal males have affected son showing that mother normal female is serving as a carrier. Trait is X-linked recessive. 

• Seed coat color has two traits- dominant and recessive.
• The dominant trait is yellow color and the recessive trait is green color.
• So, the correct answer is option A. 
  

• The mother is normal having the genotype $$X$$ $$X$$. The father is affected having the genotype X$$^h$$Y. 
• The child receives one set of chromosomes from the mother and one set from the father. 
• The child for being a male should receive the $$X$$ chromosome from mother and $$Y$$ chromosome from the father which will result the genotype of $$X$$$$Y$$. 
• So, there are no chances that the child will be hemophilic. 
• Thus, the correct answer is option A. 

A monohybrid cross is conducted between pure tall plant(TT) with pure dwarf plant(tt), in the F1 generation tall plants(Tt) are formed. When this plant is subjected to self pollinatin, in the F₂ generation 3 tall plants and 1 dwarf plant is formed. The ratio between tall and dwarf  plants is 3:1 and 1 plant with TT, 2 plants with Tt, 1 plant with tt are formed. The genotypic ratio is 1:2:1.

• Chromomeres are bead-like or granular structures present on the eukaryotic chromosome which are formed by the coiling of a continuous DNA thread.
• In areas which are devoid of chromatin the transcription and condensing of DNA and protein complexes form the chromomeres.
• It is visible under the microscope during the prophase stage of meiosis and mitosis. 
• They are also known as Idiomere.
• Chromomeres were discovered and described by Balbiani in 1876 and by Pfitzner in 1882. 
• So, the correct answer is 'Pfitzner'.

A.Pedigree analysis – A record of inheritance of certain genetic traits for two or more generations presented in the form of a diagram or family tree is called Pedigree analysis.

B.Punnet square - It is a graphical representation to indicate all possible union of gametes during fertilization and to calculate the probability of all possible genotypes of offsprings in a genetic cross.

C.Chromosome map - a technique used in autosomal DNA testing which allows the testee to determine which segments of DNA came from which ancestor. In order to map DNA segments on specific chromosomes it is necessary to test a number of close family relatives.

D.Genotypic ratio – Ratio, in which the representation of an individual’s genetical constitution with respect to a single character or set of characters.

E.Karyotype - the number and appearance of chromosomes in the nucleus of a eukaryotic cell.

In Drosophila melanogaster, the Y chromosome does not trigger male development. Instead, sex is determined by the number of X chromosomes. The D. melanogaster Y chromosome does contain genes necessary for male fertility. The y chromosome in Drosophila is not involved in determining sex, rather it contains genes active in forming sperms in adults. So, the correct option is 'True'.