What is DNA Replication?
DNA replication, in molecular biology is the biological process by which two identical copies of a DNA molecule are created. As the main part of biological inheritance, DNA replication is an essential component in all living organisms. This is necessary for cell division, growth, and repair of damaged tissue. It also ensures that each new cell receives its own copy DNA. Because cells possess the unique property of division, replication of DNA is essential.
A double helix is made up two complementary strands of DNA. Double helix refers to the appearance of double-stranded DNA. It is composed of two linear, opposite-oriented strands that twist together to form. These strands are separated during replication. Semiconservative replication is a process where each strand of the original DNA molecules serves as a template to make its counterpart. Semi-conservative reproduction results in a new helix that is composed of both an original and a newly synthesized DNA strand. Near perfect DNA replication accuracy is ensured by cellular proofreading and error-checking.
The DNA replication process in a cell begins at certain locations (or origins of replication) within the genome, which contains the genetic material for the organism. The helicase enzyme, which is responsible for unwinding DNA at the origin and the synthesis of new DNA strands, causes replication forks to grow bi-directionally away from the origin. To aid in DNA synthesis’s initiation and progression, a number of proteins are linked to the replication fork. The DNA polymerase is the most important enzyme involved in synthesizing new strands. It does this by adding nucleotides to each template strand. The S-stage of interphase is where DNA replication takes place.
In vitro DNA replication (DNA amplification), can also be done artificially outside of a cell. DNA polymerases can be isolated from cells, and artificial DNA primers may be used to initiate DNA synthesis at sequences known in a template DNA molecular. Polymerase chain reaction (PCR), ligase chain reaction (LCR), and transcription-mediated amplification (TMA) are examples. Researchers reported evidence in March 2021 that a preliminary form transfer RNA, which is a crucial component of translation and the biological synthesis (TMA) of new proteins, might have been an replicator molecule in the very early stages of life development, or abiogenesis.
What is Transcription?
Transcription refers to the process of converting a portion of DNA into RNA. Messenger RNA (mRNA) is produced when DNA segments are transcribed into RNA molecules capable of encoding proteins. Some segments of DNA can also be copied into RNA molecules known as non-codingRNAs (ncRNAs). The average mRNA quantity is greater than 10 times that of the ncRNA when it is spread across multiple cells in a tissue. However, in some cases ncRNAs can be more abundant than mRNAs in single cell types. The preponderance or mRNA is true even though less than 2 percent of the human genome can transcribe into mRNA. However, at least 80% can be active transcribed in one or more cells.
Both DNA andRNA are nucleic acid, which use base pairs nucleotides to create a complementary language. An RNA polymerase reads a DNA sequence and produces an antiparallel, complementary RNA strand, called a primary transcript.
The following steps are used to transcribe:
- Together with one or more general transcription factor(s), RNA polymerase binds to promoter genome.
- The transcription bubble is created by RNA polymerase, which splits the DNA helix into two distinct strands. This is achieved by breaking hydrogen bonds between DNA nucleotides.
- RNA polymerase also adds RNA nucleotides, which are complementary to nucleotides from one DNA strand.
- With the help of RNA polymerase, a RNA sugar-phosphate backbone is formed to form anRNA strand.
- The RNA-DNA helix hydrogen bonds break, allowing the newly synthesized RNA strand to be freed.
- The RNA can be further processed if the cell contains a nucleus. This could include polyadenylation and capping.
- The RNA can either remain in the nucleus, or it may exit the cytoplasm via the nuclear pore complex.
The RNA that is transcribed into an RNA molecule encodes a protein is called messenger RNA (mRNA). The mRNA serves as a template to the protein’s formation through translation. Other DNA stretches can be transscribed into smaller non-codingRNAs, such as microRNA or transfer RNA(tRNA), small nucleolarRNA (snoRNA), and small nuclearRNA (snRNA). Enzymatic RNA molecules known as ribozymes may also be used to translate larger non-codingRNAs like ribosomalRNA (rRNA) and long noncodingRNA (lncRNA). RNA is essential for the function of a cell. It regulates, synthesizes, and processes proteins.
The term transcription is also used in virology to refer to mRNA synthesizing from an RNA molecular (i.e. equivalent to RNA replication). The genome of a single-stranded single-sense RNA virus (ssRNA–) may serve as a template for a single-stranded positive-sense RNA (+) [clarification required]. Because the positive-sense sequence information contains the sequence information necessary to translate the viral proteins required for viral replication, this is possible. A viral RNA replicase catalyzes this process.
Differences between DNA Replication and Transcription – DNA Replication vs Transcription
Differences between DNA Replication and Transcription:
| Character | DNA Replication | Transcription |
|---|---|---|
| Definition | The process of making new copies of DNA. | The process by which DNA is copied (transcribed) to RNA. |
| Significance | Important for properly regulating the growth and division of cells. | Regulates gene expression. |
| Transfer of Genetic Information | From DNA to DNA. | From DNA to RNA. |
| Occurs during | S phase of cell cycle. | G1 and G2 phases of cell cycle. |
| Motive | Occurs in preparation for cell division. | Occurs in preparation for protein translation. |
| Involved in | Cell division. | Gene expression. |
| Raw Materials | dATP, dGTP, dTTP, and dCTP serve as raw materials. | ATP, UTP, GTP, and CTP serve as raw materials. |
| Template | Both DNA strands. | Single DNA strand. |
| Primers | Requires RNA primer to start replication. | No primer is required for initiation. |
| Enzymes Required | DNA Helicase, DNA Polymerase. | Transcriptase (type of DNA Helicase), RNA polymerase. |
| Unwinding and Splitting | Involves unwinding and splitting of the entire DNA molecule. | Involves unwinding and splitting of only those genes which are to be transcribed. |
| Base pairing | Adenine pairs with thymine. | Adenine pairs with uracil instead of thymine. |
| Copying of Template | The entire template strand is copied. | Only the portion of the template DNA that codes for required genes is transcribed, or copied. |
| Product | Two daughter DNA. | mRNA, tRNA, rRNA, and non-coding RNA (like microRNA). |
| Strands in product | Double stranded DNA. | Single stranded RNA. |
| Post-formation | Joining of Okazaki fragments. | RNA editing. |
| Processing | Produces normal DNA molecules that do not need any processing. | Produces primary RNA transcript molecule which needs processing to acquire final form and size. |
| Bond | Replicated DNA strand remains hydrogen bonded to its template DNA strand. | Transcribed RNA strand separates from its DNA template strand. |
| Migration from the site of formation | Products remain within the nucleus. | Greater part of the product passes from the nucleus into the cytoplasm. |
| Degradation of Product formed | Products are not degraded. | Products are degraded after their function is over. |
| Rate of Production | The rate of replication is typically 20 times faster than transcription, and six or more replication forks may be present at the same time on the chromosome. | Comparatively slower. |
| Process followed by | Transcription/ Next replication. | Translation. Although some RNA are the final product themselves. |
| Significance | Conserves the entire genome for the next generation. | Necessary for protein synthesis. |
