Who is credited with proposing the Chromosomal Theory of Inheritance?
Sutton and Boveri proposed that genes are located on chromosomes that undergo segregation and independent assortment.
Question 122 of 519
📘 CLASS XII
The cross mentioned in the text: Tall plant with yellow seeds (TtYy) and a Tall plant with green seed (Ttyy). What proportion of the offspring are expected to be Tall and Green?
This is a dihybrid cross: (Tt x Tt) × (Yy x yy). Probability Tall = 3/4, Green = 1/2 → overall = 3/8.
Question 123 of 519
📘 CLASS XII
If the two loci for the cross TtYy × Ttyy were linked, what would be the distribution of phenotypic features in the offspring compared to independent assortment?
Linkage increases parental combination frequency and decreases recombinant types.
Question 124 of 519
📘 CLASS XII
Which term describes the phenomenon where a single gene influences multiple phenotypic traits?
Pleiotropy occurs when one gene affects multiple unrelated characteristics, e.g., phenylketonuria gene.
Question 125 of 519
📘 CLASS XII
The allelic interaction where both alleles are expressed equally in the heterozygote, such as in the roan coat color of cattle (RW), is called:
In co-dominance, both alleles are equally expressed, showing characteristics of both parents.
Question 126 of 519
📘 CLASS XII
When two heterozygous parents (Bb) are crossed, the probability of the offspring being heterozygous is:
Cross Bb × Bb gives BB, Bb, Bb, bb — 2 out of 4 (½) are heterozygous.
Question 127 of 519
📘 CLASS XII
What is the term for a gene that expresses itself only in the homozygous condition?
A recessive gene expresses only when two identical alleles are present (tt or rr).
Question 128 of 519
📘 CLASS XII
In the cross Tt × tt, what is the expected ratio of Tall to Dwarf offspring?
A monohybrid test cross Tt × tt produces 1 Tall : 1 Dwarf.
Question 129 of 519
📘 CLASS XII
Which of the following is NOT an exception to Mendelian principles?
The Law of Segregation is a core Mendelian principle, not an exception.
Question 130 of 519
📘 CLASS XII
What is the physical basis for the Law of Independent Assortment?
Independent assortment is physically demonstrated by the random and independent orientation of each pair of homologous chromosomes at Metaphase I of meiosis.
