What is the function of telomeres during DNA replication?
Telomeres are the physical ends of eukaryotic chromosomes. They protect chromosome ends from DNA degradation, recombination, and DNA end fusions, and they are important for nuclear architecture. Telomeres provide a mechanism for their replication by semiconservative DNA replication and length maintenance by telomerase.
Why are telomeres a necessary component of linear chromosomes?
Why are telomeres a necessary component of linear chromosomes? They maintain the length of a chromosome because DNA is shortened every time it is replicated.
Does telomerase act on leading strand?
In the leading strand, synthesis continues until the end of the chromosome is reached. The discovery of the enzyme telomerase (Figure 1) helped in the understanding of how chromosome ends are maintained. The telomerase enzyme contains a catalytic part and a built-in RNA template.
What would happen if telomerase stopped working?
Cancer is a disease characterised by the rapid and uncontrolled division of cells. Without telomerase activity, these cells would become inactive, stop dividing and eventually die. Drugs that inhibit telomerase activity, or kill telomerase-producing cells, may potentially stop and kill cancer cells in their tracks.
What are the functions of Primase?
Primase is an enzyme that synthesizes short RNA sequences called primers. These primers serve as a starting point for DNA synthesis. Since primase produces RNA molecules, the enzyme is a type of RNA polymerase.
What happens if Primase is not present?
Primase is required for the primer formation and to start the replication process by DNA polymerase. If primase is absent, DNA polymerase cannot initiate the process of replication because it can only add nucleotides to the growing chain.
Why are Okazaki fragments called Okazaki fragments?
In 1968, Okazaki discovered the way in which the lagging strand of DNA is replicated via fragments, now called Okazaki fragments. When samples were taken from the bottom of the test tube, it was found that half were heavy and half were light, proving that half of the DNA was complete and half was in fragments.
Which enzyme adds the primer to the DNA strand?
What happens if transcription goes wrong?
Mutations that happen during Transcription and Translation What happens if there is a mistake (mutation) in the DNA code? Possibly proteins won’t be made or are made improperly. If the mutations occur in the gametes, the offspring’s DNA will be affected positively, negatively, or neutrally.
What enzyme proofreads and repairs DNA?
What are the 3 types of mutations?
There are three types of DNA Mutations: base substitutions, deletions and insertions. Single base substitutions are called point mutations, recall the point mutation Glu —–> Val which causes sickle-cell disease. Point mutations are the most common type of mutation and there are two types.
What are the 5 types of mutations?
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- Missense mutation. Credit: U.S. National Library of Medicine.
- Nonsense mutation. Credit: U.S. National Library of Medicine.
- Insertion mutation. Credit: U.S. National Library of Medicine.
- Deletion mutation.
- Duplication mutation.
- Frameshift mutation.
- Repeat expansion mutation.
What is the difference between a silent mutation and a missense mutation?
A silent mutation is a mutation in which a single nucleotide base is changed, but that change does not effect the amino acid sequence. A missense mutation is a point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid.
What is the difference between a silent mutation and a neutral mutation?
Silent mutation is a mutation that does not change the amino acids sequence of the encoded protein. Neutral mutation, on the other hand, is a mutation that has no observable effect on the organism’s fitness.