Table of Contents
- 1 What are the protective caps on chromosomes?
- 2 What are chromosomes protected by?
- 3 Where are telomeres found?
- 4 What is telomerase in DNA replication?
- 5 What are telomeres and their function?
- 6 Why do chromosomes have telomeres?
- 7 What causes the overhang at the leading strand end of the chromosome?
- 8 Where is the last RNA primer located on the chromosome?
What are the protective caps on chromosomes?
When we think of the DNA that makes up our chromosomes, we usually focus on our genes. But at the end of every chromosome in our body lies a long chain of repetitive DNA called a telomere, which acts as a protective cap.
What are chromosomes protected by?
Carol Greider and Elizabeth Blackburn identified telomerase, the enzyme that makes telomere DNA. These discoveries explained how the ends of the chromosomes are protected by the telomeres and that they are built by telomerase. If the telomeres are shortened, cells age.
Does chromosome protect DNA?
Telomeric Chromatin and Chromosome Chromatin upon DNA Damage Besides the shelterin complex, telomeres have a condensed chromatin structure as an additional protection against DNA damage. Genomic nucleosomes consist of core histones H2A, H2B, H3, and H4 that form the histone octamer which is wrapped by ~147 bp DNA.
What is the term for the chromosome cap and how does it change in response to aging?
Telomeres are protective caps at the ends of chromosomes that become shorter with each cell division. For two people of the same chronological age, the person with shorter telomeres has an increased risk of developing age-related diseases such as Alzheimer’s or cancer, and even a shorter life expectancy.
Where are telomeres found?
chromosomes
Telomeres are found at the ends of chromosomes; they provide the answer to two problems of chromosome management.
What is telomerase in DNA replication?
Telomerase adds complementary RNA bases to the 3′ end of the DNA strand. Once the 3′ end of the lagging strand template is sufficiently elongated, DNA polymerase adds the complementary nucleotides to the ends of the chromosomes; thus, the ends of the chromosomes are replicated.
How chromosomes are protected by telomeres and the enzyme telomerase?
Blackburn and Szostak found that chromosomes without telomeres are protects them from degradation. Greider and Blackburn identified the enzyme that helps telomeres to protect the chromosomes – telomerase. The RNA is complementary to the telomere sequence, which allows the telomeres to be copied efficiently.
What happens in G2 G2?
Gap 2 Phase The last part of interphase is called the G2 phase. The cell has grown, DNA has been replicated, and now the cell is almost ready to divide. This last stage is all about prepping the cell for mitosis or meiosis. During G2, the cell has to grow some more and produce any molecules it still needs to divide.
What are telomeres and their function?
Telomeres are DNA-protein structures that form protective caps at the end of eukaryotic chromosomes. They constitute the safeguards of chromosome degradation and are responsible for maintaining genomic integrity.
Why do chromosomes have telomeres?
Telomeres are repetitive nucleotide sequences at each end of chromosomes. Their function is to protect the ends of the chromosomes from deterioration or fusion to other chromosomes during cell division. With every cell division, telomeres shorten. This blocks further cell division and induces senescence.
What is the protective cap of DNA on the tip of chromosomes?
The telomere is the protective cap of DNA on the tip of chromosomes. You lose a small amount of these telomeres each time the cell divides. Eventually the telomeres be lost as you age.
How are telomeres used to protect the chromosomes?
Telomeres act as caps that protect the internal regions of the chromosomes, and they’re worn down a small amount in each round of DNA replication. In this article, we’ll take a closer look at why telomeres are needed, why they shorten during DNA replication, and how the enzyme telomerase can be used to extend them.
What causes the overhang at the leading strand end of the chromosome?
The overhang at the lagging strand end of the chromosome is due to incomplete end replication (see figure above). The overhang at the leading strand end of the chromosome is actually generated by enzymes that cut away part of the DNA.
Where is the last RNA primer located on the chromosome?
In human cells, the last RNA primer of the lagging strand may be positioned as much as to nucleotides away from the chromosome end. Thus, the single-stranded overhangs produced by incomplete end replication in humans are fairly long, and the chromosome shortens significantly with each round of cell division.