There are three types of repair mechanisms: direct reversal of the damage, excision repair, and postreplication repair. Direct reversal repair is specific to the damage. For example, in a process called photoreactivation, pyrimidine bases fused by UV light are separated by DNA photolyase (a light-driven enzyme).
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What are the three steps in DNA repair?
There are three types of repair mechanisms: direct reversal of the damage, excision repair, and postreplication repair. Direct reversal repair is specific to the damage. For example, in a process called photoreactivation, pyrimidine bases fused by UV light are separated by DNA photolyase (a light-driven enzyme).
What are the 3 DNA processes?
DNA replication steps. There are three main steps to DNA replication: initiation, elongation, and termination. In order to fit within a cell’s nucleus, DNA is packed into tightly coiled structures called chromatin, which loosens prior to replication, allowing the cell replication machinery to access the DNA strands.
What binds Okazaki fragments?
Newly synthesized DNA, otherwise known as Okazaki fragments, are bound by DNA ligase, which forms a new strand of DNA. There are two strands that are created when DNA is synthesized.
Is the leading strand 5 to 3?
One new strand, which runs 5′ to 3′ towards the replication fork, is the easy one. This strand is made continuously, because the DNA polymerase is moving in the same direction as the replication fork. This continuously synthesized strand is called the leading strand.
What is another name for a replication fork?
Synonyms
| Synonym | Type |
|---|---|
| replication focus | related |
What does 3 and 5 DNA mean?
The 5′ and 3′ mean “five prime” and “three prime”, which indicate the carbon numbers in the DNA’s sugar backbone. The 5′ carbon has a phosphate group attached to it and the 3′ carbon a hydroxyl (-OH) group. This asymmetry gives a DNA strand a “direction”.
What triggers DNA replication?
Replication occurs in three major steps: the opening of the double helix and separation of the DNA strands, the priming of the template strand, and the assembly of the new DNA segment. During separation, the two strands of the DNA double helix uncoil at a specific location called the origin.
Is RNA built 5 to 3?
RNA growth is always in the 5′ → 3′ direction: in other words, nucleotides are always added at a 3′ growing tip, as shown in Figure 10-6b. Because of the antiparallel nature of the nucleotide pairing, the fact that RNA is synthesized 5′ → 3′ means that the template strand must be oriented 3′ → 5′.
Why is replication called semi conservative?
As the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions. This process is known as semi-conservative replication because two copies of the original DNA molecule are produced. Each copy contains one original strand and one newly-synthesized strand.
What does 3 Prime mean?
3′ (3-prime) MGI Glossary. Definition. A term that identifies one end of a single-stranded nucleic acid molecule. The 3′ end is that end of the molecule which terminates in a 3′ phosphate group.
Is the lagging strand synthesized 5 to 3?
Both the Okazaki fragments and the leading strand are synthesized in the 5′ → 3′ direction. The discontinuous assembly of the lagging strand enables 5′ → 3′ polymerization at the nucleotide level to give rise to overall growth in the 3′ → 5′ direction.
Why can nucleotides only be added to the 3 end?
DNA Polymerase can only add nucleotides at the -OH group which is on the 3′ end. This free -OH group is necessary because it can carry out a nucleophilic attack on phosphate group of the incoming deoxyribonucleoside triphosphate which would contain the base that is complementary to the template strand.
Why is it called 5 and 3?
Each end of DNA molecule has a number. One end is referred to as 5′ (five prime) and the other end is referred to as 3′ (three prime). The 5′ and 3′ designations refer to the number of carbon atom in a deoxyribose sugar molecule to which a phosphate group bonds.