Final answer:
The chromosomal theory of inheritance states that d.) is that genes for phenotypic traits are carried on chromosomes.
Step-by-step explanation:
The chromosomal theory of inheritance states that genes for phenotypic traits are carried on chromosomes. It was proposed because the behavior of chromosomes in mitosis is similar to that of genes during gamete formation. The theory was supported by observations made by scientists such as Theodor Boveri and Walter Sutton, who observed the role of chromosomes in embryonic development and meiosis, respectively.
Chromosomes are composed of DNA and proteins, and they carry segments called genes that code for traits. During meiosis, chromosomes separate and are passed on from parents to offspring. The Chromosomal Theory of Inheritance provides an understanding of how traits are inherited and passed on through generations.
The theory also explains Mendel's laws of inheritance. The law of segregation states that alleles for a trait separate during gamete formation, and the law of independent assortment states that alleles for different traits segregate independently of each other. Both of these laws can be explained by the behavior of chromosomes and the random segregation of genes during meiosis. Therefore the correct answer is d.) is that genes for phenotypic traits are carried on chromosomes