Question

X-chromosome or X-body was first observed by.
A)Mendel (1901)
B)Castle (1910)
C)Henking (1891)
D)Bateson (1906)

Answer 1

Mendel told that something was being stably passed down, unchanged. from parent to offspring through the gametes, over successive generations. He called these things as 'factors' We now call these factors as "genes". Therefore, a gene is defined as the functional unit of inheritance. The gene contain information that is required to express a particular trait in organism

Complete answer:
Holandric traits are the traits that are passed from male to male only that is from father to son. There are two sex hormones present in human male X and Y. But X chromosome is common to both male and females. Y is unique only to male .X-chromosome does not pass directly from one parent to the offspring of the same sex but follows a criss-cross inheritance, i.e., it is transferred from one sex to the offspring of the opposite sex. In other words, in criss-cross inheritance a male transmits his traits to his grandson through daughter (Diagynic), while a female transmits the traits to her granddaughter through her son (Diandric). So, they are called criss cross inheritance.

Now let us find solution from given options:
Mendel (1901): he worked on the pea and took seven contrasting characters of pea. He talked about alleles and genes.
Castle (1910) : he told how to prepare grafts in flowers and skeletons in animals.
Henking (1891) : while working on the testicles he found that one chromosome does not pass during meiosis and named it as X chromosomes.
Bateson (1906) : he coined the term pure line in genetics.

Hence, the correct answer is option (C)

Note: There are present sex limited and sex influence traits according to presence of X chromosome.
Sex limited traits :- The genes of sex limited traits are autosomal and they are found in both sexes but express in one sex only. Examples: (i) Milk glands in female (ii) Beard in man
Sex influenced traits :- These are the autosomal genes that are influenced by the sex of the bearer. These traits appear more frequently in one sex than in the other.