What are the two types of DNA repair?
The different types of DNA repair include direct repair, base excision repair, nucleotide excision repair (NER), double-strand break repair (including homologous recombination and nonhomologous end joining), and crosslink repair (Sancar et al., 2004).
What is the result of transcription?
The individual nucleotides that are read off of the DNA template strand are transcribed into the nucleotides of the corresponding RNA, so the final result is a single-stranded polymer, namely the mRNA, whose nucleotides correspond exactly to the complementary nucleotides on the DNA strand with the exception that …
What is DNA replication called?
semiconservative replication
What is DNA repair system?
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell’s ability to transcribe the gene that the affected DNA encodes.
What is the process of transcription and translation?
Transcription takes place in the nucleus. It uses DNA as a template to make an RNA molecule. RNA then leaves the nucleus and goes to a ribosome in the cytoplasm, where translation occurs. Translation reads the genetic code in mRNA and makes a protein.
What are the steps of DNA transcription?
Transcription involves four steps:
- Initiation. The DNA molecule unwinds and separates to form a small open complex.
- Elongation. RNA polymerase moves along the template strand, synthesising an mRNA molecule.
- Termination. In prokaryotes there are two ways in which transcription is terminated.
- Processing.
Where does DNA replication happen?
DNA replication occurs in the cytoplasm of prokaryotes and in the nucleus of eukaryotes. Regardless of where DNA replication occurs, the basic process is the same. The structure of DNA lends itself easily to DNA replication. Each side of the double helix runs in opposite (anti-parallel) directions.
What are 2 main types of mutations?
Two major categories of mutations are germline mutations and somatic mutations.
- Germline mutations occur in gametes. These mutations are especially significant because they can be transmitted to offspring and every cell in the offspring will have the mutation.
- Somatic mutations occur in other cells of the body.
What best describes the process of transcription?
Transcription is the process of transcribing the DNA code into another type of code or message – mRNA (messenger RNA). An enzyme called RNA polymerase binds to a specific part of a DNA sequence called the promoter (this acts as a signal to the cell to begin transcription).
What is the importance of DNA replication occurring without any mistakes?
This mutation will pass to all progeny cells and can cause lethal consequences, such as development of cancer. Thus, DNA replication without any mistake is important to prevent mutations and keeping organisms in a stable healthy state.
What are the 3 basic steps of transcription?
Transcription takes place in three steps: initiation, elongation, and termination. The steps are illustrated in Figure 2.
What step of DNA replication is the most important?
2) One of the most important steps of DNA Replication is the binding of RNA Primase in the the initiation point of the 3′-5′ parent chain.
What is the role of enzymes in the DNA replication process?
DNA polymerase enzymes bind to and dissociate from template DNA repeatedly during the replication or repair process. The number of synthesized nucleotides added by the DNA polymerase per one binding event is defined as processivity.
What is DNA replication Why is it important?
Replication is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, as the parent cell. Once the DNA in a cell is replicated, the cell can divide into two cells, each of which has an identical copy of the original DNA.
What problems can occur with DNA replication?
DNA replication is a highly accurate process, but mistakes can occasionally occur, such as a DNA polymerase inserting a wrong base. Uncorrected mistakes may sometimes lead to serious consequences, such as cancer. Repair mechanisms correct the mistakes.
What happens if DNA polymerase is not present?
When strand slippage occurs during DNA replication, a DNA strand may loop out, resulting in the addition or deletion of a nucleotide on the newly-synthesized strand. But if this does not occur, a nucleotide that is added to the newly synthesized strand can become a permanent mutation.
What is DNA repair and why is it important?
DNA repair, any of several mechanisms by which a cell maintains the integrity of its genetic code. DNA repair ensures the survival of a species by enabling parental DNA to be inherited as faithfully as possible by offspring. It also preserves the health of an individual.
Where is the process of translation located?
ribosomes
What is the first step of DNA replication?
The first step in DNA replication is to ‘unzip’ the double helix structure of the DNA? molecule. This is carried out by an enzyme? called helicase which breaks the hydrogen bonds? holding the complementary? bases? of DNA together (A with T, C with G).
Which of the following prevents hydrogen bonding between DNA strands during replication?
| Table 1. The Molecular Machinery Involved in Bacterial DNA Replication | |
|---|---|
| Enzyme or Factor | Function |
| Single-stranded binding proteins | Bind to single-stranded DNA to prevent hydrogen bonding between DNA strands, reforming double-stranded DNA |
| Sliding clamp | Helps hold DNA pol III in place when nucleotides are being added |
Is prokaryotic DNA replication Semiconservative?
DNA synthesis is a process that all living organisms must perform. For most eukaryotes and prokaryotes, the process of DNA synthesis is done semiconservatively. Semiconservative replication for E. Coli is initiated by way of a replicon structure which behaves as an autonomous unit of DNA replication.
Which one is useful in prokaryotes replication?
Mesosomes serve in DNA replication and guide distribution of duplicated bacterial chromosomes into the two daughter cells during cell division. They also carry the enzymes for aerobic respiration and increase the surface area for the same.
What is the difference between mismatch repair and nucleotide excision repair quizlet?
What is the difference between mismatch repair and nucleotide excision repair? In mismatch repair, one nucleotide is replaced, whereas in nucleotide excision repair several nucleotides are replaced. You just studied 29 terms!
What is the correct order for the following events in excision repair of DNA?
What is the correct order for the following events in excision repair of DNA? (1) DNA polymerase I adds correct nucleotides by 5′-to-3′ replication; (2) damaged nucleotides are recognized; (3) DNA ligase seals the new strand to existing DNA; (4) part of a single strand is excised.
Which statement is true with respect to mismatch repair and nucleotide excision repair NER )?
Which statement is true with respect to mismatch repair and nucleotide excision repair (NER)? Mismatch repair fixes thymine dimers caused by exposure to UV light, while NER fixes errors in DNA replication.
How is DNA replication in prokaryotes?
DNA Replication in Prokaryotes: A replication fork is formed when helicase separates the DNA strands at the origin of replication. The DNA tends to become more highly coiled ahead of the replication fork. DNA ligase seals the gaps between the Okazaki fragments, joining the fragments into a single DNA molecule.
What is a thymine dimer?
Cyclobuthane thymine dimer is a photolesion produced by UV radiation in sunlight and is considered as a potential factor causing skin cancer. It is formed as a covalently bonded complex of two adjacent thymines on a single strand of DNA.
What are the steps of DNA repair?
At least five major DNA repair pathways—base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR) and non-homologous end joining (NHEJ)—are active throughout different stages of the cell cycle, allowing the cells to repair the DNA damage.
What is the difference between base excision repair and mismatch repair?
In base excision repair, just the damaged base is removed. In nucleotide excision repair, as in the mismatch repair we saw above, a patch of nucleotides is removed.
Is DNA replication bidirectional or unidirectional?
Bidirectional replication of DNA is the mechanism employed in all eukaryotic and most prokaryotic cells. Unidirectional replication is rare and appears to occur in only a limited number of prokaryotes.
What is unique about prokaryotic DNA replication?
The origin of replication is approximately 245 base pairs long and is rich in AT sequences. This sequence of base pairs is recognized by certain proteins that bind to this site. An enzyme called helicase unwinds the DNA by breaking the hydrogen bonds between the nitrogenous base pairs.
Are phosphodiester bonds broken during DNA replication?
When the bond between the phosphates is broken, the energy released is used to form the phosphodiester bond between the incoming nucleotide and the growing chain….Summary.
| Prokaryotic DNA Replication: Enzymes and Their Function | |
|---|---|
| Enzyme/protein | Specific Function |
| Primase | Synthesizes RNA primers needed to start replication |
Why does DNA replication occur from 5 to 3?
DNA is always synthesized in the 5′-to-3′ direction, meaning that nucleotides are added only to the 3′ end of the growing strand. As shown in Figure 2, the 5′-phosphate group of the new nucleotide binds to the 3′-OH group of the last nucleotide of the growing strand.
Why DNA replication is bidirectional?
In bidirectional, none of the two ends will be stationary and both will be moving. Therefore, bidirectional replication involves replicating DNA in two directions at the same time resulting in a leading strand and a lagging strand.
What enzyme is in base excision repair?
DNA glycosylase
How replication is termination in prokaryotes?
Termination of DNA replication occurs when two oppositely orientated replication forks meet and fuse, to create two separate and complete double‐stranded DNA molecules. Failure to terminate bacterial chromosome replication correctly results in chromosome over‐replication and genome instability.
Is DNA replication in prokaryotes conservative?
The genetic material must be faithfully replicated to assure heredity. Unlike in eukaryotes, pyrimidine deoxyribonucleotides are synthesized from ribonucleotide diphosphates rather than triphosphates. The replication takes place in a semi-conservative manner semi-conservative replication.
What does nucleotide excision repair fix?
In nucleotide excision repair (NER), damaged bases are cut out within a string of nucleotides, and replaced with DNA as directed by the undamaged template strand. This repair system is used to remove pyrimidine dimers formed by UV radiation as well as nucleotides modified by bulky chemical adducts.
What is unidirectional DNA replication?
A replication eye may represent unidirectional replication (when only one end moves) or a bidirectional replication (when both ends move). Fig. 26.10. The difference between unidirectional and bidirectional replications in the movement of replication forks.
Is DNA replication always bidirectional?
DNA replication is bidirectional from the origin of replication. To begin DNA replication, unwinding enzymes called DNA helicases cause short segments of the two parent DNA strands to unwind and separate from one another at the origin of replication to form two “Y”-shaped replication forks.