Chapter 9, Problem 1R

Compare and contrast the following terms:

1. a. cDNA and gene
2. b. restriction fragment and gene
3. c. DNA probe and gene
4. d. DNA polymerase and DNA ligase
5. e. rDNA and cDNA
6. f. genome and proteome

Summary Introduction

To review:

The similarities and differences between the given terms: cDNA and gene, RFLP and gene, DNA probe and gene, DNA polymerase and DNA ligase, rDNA and cDNA, genome and proteome.

Introduction:

A genome represents the entire set of genetic material of an organism. It is stored in chromosomes and contains all the information required for growth and the survival of that organism. Genes are DNA that contain instructions either for coding a specific protein or to perform a specific function. Eukaryotic genes consist of two parts, namely exon (coding regions) and intron (non-coding regions). The flow of genetic information from DNA to RNA (transcription) and RNA to protein (translation) is known as the central dogma of molecular biology. Messenger RNA, a single stranded nucleotide sequence, is called as the sense strand since it is the code of a product (protein). A complete set of proteins coded by an organism’s genome is referred to as proteome.

Explanation of Solution

Tabular representation:

S.NO.	TERMS	SIMILARITIES	DIFFERENCES
a.	cDNA	DNA	DNA synthesized from mature mRNA (reverse transcriptase enzyme)
	Gene		DNA that codes for a specific protein or function
b.	RFLP	DNA	Digested fragments of DNA (restriction enzyme)
	Gene		DNA that codes for a specific protein or function
c.	DNA probe	DNA	Short stretches of labelled DNA to identify clones
	Gene		DNA that codes for a specific protein or function
d.	DNA polymerase	Enzyme	Enzyme which catalyzes the DNA synthesis
	DNA ligase		Enzyme that links the backbone of DNA strands
e.	rDNA	DNA	DNA made by joining DNA molecules from different sources
	cDNA		DNA synthesized from mature mRNA (reverse transcriptase enzyme)
f.	Genome		Entire set of genetic material of an organism
	Proteome		Complete protein set expressed by a genome

Explanation:

1. a. cDNA and Gene

Synthesis of DNA from a mature mRNA strand is catalysed by reverse transcriptase enzyme. The DNA synthesized is referred to as complementary DNA (cDNA).

DNA that contains instructions either for coding a specific protein or to perform a specific function is known as a gene.

1. b. RFLP and Gene

Using restriction enzymes, DNA under study can be digested into thousands of pieces of different sizes. These fragments of DNA are referred to as restriction fragment length polymorphism (RFLP).

DNA that contains instructions either for coding a specific protein or to perform a specific function is known as a gene.

1. c. DNA probe and Gene

In the laboratory, genes which confer an interested phenotype (enzyme or drug-resistance) can be isolated and integrated into a vector. These recombinant vectors taken up by a cell (bacterial or eukaryotic cells) can be grown in an ideal medium to produce many genetically identical copies of the gene. Clone refers to the production of identical cells carrying a desired plasmid. Short stretches of labelled DNA (single-stranded) that are complementary to the gene of interest are synthesized. They are referred to as DNA probes and are used in the identification of clones. On finding the appropriate match, DNA probes bind to the target gene. In order to facilitate detection, such DNA probes are labelled with epitopes, fluorophores or radioisotopes.

DNA that contains instructions either for coding a specific protein or to perform a specific function is known as a gene.

1. d. DNA polymerase and DNA ligase

DNA polymerase is an enzyme which catalyses the synthesis of DNA using four deoxyribonucleotides (building blocks of DNA).

DNA ligase is an enzyme which facilitates the ligation of DNA strands (joining two fragments of nucleic acid). It catalyses the formation of two covalent phosphodiester bonds between the 5′ phosphate end of one nucleotide and 3′ hydroxyl end of another.

1. e. rDNA and cDNA

In recombinant DNA technology, genes which confer an interested phenotype (drug-resistant genes) can be isolated and integrated into a vector. Such vectors, DNA molecule, act as a vehicle and aid in the transfer of foreign genes into another cell (bacterial or eukaryotic cell). DNA molecules, artificially modified in laboratory conditions that carry desired genes isolated from different organisms, are referred to as recombinant DNA (rDNA).

The synthesis of DNA from a mature mRNA is catalysed by reverse transcriptase enzyme. The DNA synthesized is referred to as complementary DNA (cDNA).

1. f. Genome and proteome

Genome represents the entire set of genetic materials of an organism. Complete set of proteins coded by an organism’s genome is referred to as proteome.

Conclusion

The similarities and differences between cDNA and gene, RFLP and gene, DNA probe and gene, DNA polymerase and DNA ligase, rDNA and cDNA, genome and proteome are described.