Chapter 11, Problem 1MC

The physical position of a gene on a chromosome is its _______ slightly different forms of a gene are called_________.

a. locus; alleles

b. locus; polygenic

c. chiasma; alleles

d. trait; hybrids

Summary Introduction

Introduction:

Genes are the primary structural and functional units of heredity. These are basically the sequences of nucleotides containing the bases, namely; A (adenine), T (thymine), G (guanine), and C (cytosine). Genes are precisely located on the chromosomes. Mutations in the genes often lead to the deoxyribonucleic acid (DNA) damage or the disruptive phenotypic traits.

Answer to Problem 1MC

Correct answer:

Locus is being defined as the position where the gene resides on chromosomes. Also, the alleles are known to be the variable forms of genes.

Explanation of Solution

Explanation for the correct statement:

Option (a) given for the definition of locus: The place where the genes are located along with the definition of alleles: The unidentical form of the genes is correct. As, the locus is generally defined in a way as the definite position at which genes are located on the chromosomes, whereas allele is the unidentical forms of the gene present on different chromosomes. Therefore, this option is correct.

Explanation for incorrect answer:

Option (b) as given for the definition of the locus, is the position at, which genes are placed, is correct. On the contrary, variable forms of genes are called polygenic. The term ‘polygenic’ governs two or more than two genes on a single phenotypic character. So, it is the incorrect answer.

Option (c) defined the locus as the position at, which chiasma is placed, along with the definition of an allele as the variable form of the genes. As chiasma is defined as the point at, which the information gets exchanged between the chromatids that are also known as chromosomal crossing over. So, it is the incorrect answer.

Option (d) provided the definition of the locus as the position where traits are placed on chromosomes, and different forms of a gene to be the hybrids. Traits are described as the unique characteristics in an individual which makes one person different from the other in many forms and features, and hybrid is formed when the parents involved are from different species or subspecies. So, it is the incorrect answer.

Hence, option (b), (c), and (d) are incorrect.

Conclusion

Therefore, it can be concluded that genes carrying the information in the form of bases, codes for different proteins are found at a specific place on the chromosome known as a locus, and the unidentical forms of the genes are known as alleles.