What is a telomeric DNA sequence?

Telomeres are sections of DNA? found at the ends of each of our chromosomes?. They consist of the same sequence of bases?repeated over and over. In humans the telomere sequence is TTAGGG. This sequence is usually repeated about 3,000 times and can reach up to 15,000 base pairs? in length.

How is telomeric DNA replicated?

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.

Are telomeres on 3 or 5?

Telomeres consist of hundreds or thousands of repeats of the same short DNA sequence, which varies between organisms but is 5′-TTAGGG-3′ in humans and other mammals. Telomeres need to be protected from a cell’s DNA repair systems because they have single-stranded overhangs, which “look like” damaged DNA.

Where is telomeric DNA located?

The telomere is a nucleoprotein complex located at the ends of eukaryotic chromosomes. It is essential for maintaining the integrity of the genome. It is not a linear structure and, for much of the cell cycle, telomeric DNA is maintained in a loop structure, which serves to protect the vulnerable ends of chromosomes.

How is a telomere made?

Telomeres are made up of repeated segments of DNA that consist of the sequence 5′-TTAGGG-3′ (in which T, A, and G are the bases thymine, adenine, and guanine, respectively). Some human cells contain as many as 1,500 to 2,000 repeats of this sequence at each end of each chromosome.

In which direction does DNA replication take place?

5′-to-3′ direction
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.

What is the purpose of the 3 ‘- to 5 exonuclease activity of DNA polymerase?

The 3′–>5′ exonuclease activity intrinsic to several DNA polymerases plays a primary role in genetic stability; it acts as a first line of defense in correcting DNA polymerase errors. A mismatched basepair at the primer terminus is the preferred substrate for the exonuclease activity over a correct basepair.

Is telomerase on the leading strand?

The telomerase enzyme contains a catalytic part and a built-in RNA template. It attaches to the end of the chromosome, and complementary bases to the RNA template are added on the 3′ end of the DNA strand.

Is the leading strand always 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.

How is telomeric DNA synthesized?

Synthesis of Telomeric DNA: Synthesis of the telomeric repeating sequences has been well understood in Tetrahymena. In this species an enzymes called telomerase was discovered in 1987 by Greider and Blackburn; this enzyme synthesize the telomeric DNA.

What is telomere structure and synthesis?

Contact Us Return to Content Structure and Synthesis of Telomere Article Shared by ADVERTISEMENTS: In this article we will discuss about the structure and synthesis of telomere. Structure of Telomere: Molecular genetic studies have shown that the telomere consists of several short sequences which are tandemly repeated (Table 8.8).

Why do Eukaryotic telomeres have a single stranded DNA overhang?

Eukaryotic telomeres normally terminate with 3′ single-stranded-DNA overhang, which is essential for telomere maintenance and capping. Multiple proteins binding single- and double-stranded telomere DNA have been identified. These function in both telomere maintenance and capping.

What is the purpose of the telomeric loop?

This loop is analogous to a knot, which stabilizes the telomere, and prevents the telomere ends from being recognized as breakpoints by the DNA repair machinery. Should non-homologous end joining occur at the telomeric ends, chromosomal fusion would result.