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Related Concept Videos

Telomeres and Telomerase02:41

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In eukaryotic DNA replication, a single-stranded DNA fragment remains at the end of a chromosome after the removal of the final primer. This section of DNA cannot be replicated in the same manner as the rest of the strand because there is no 3’ end to which the newly synthesized DNA can attach. This non-replicated fragment results in gradual loss of the chromosomal DNA during each cell duplication. Additionally, it can induce a DNA damage response by enzymes that recognize single-stranded...
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In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high fidelity before cell division, so there are many proteins that fulfill specialized roles in the replication process. Replication occurs in three phases: initiation, elongation, and termination, and ends with two complete sets of chromosomes in the nucleus.
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Replicative cell senescence is a property of cells that allows them to divide a finite number of times throughout the organism's lifespan while preventing excessive proliferation. Replicative senescence is associated with the gradual loss of the telomere — short, repetitive DNA sequences found at the end of the chromosomes. Telomeres are bound by a group of proteins to form a protective cap on the ends of chromosomes. Embryonic stem cells express telomerase — an enzyme that adds...
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Transcription elongation is a dynamic process that alters depending upon the sequence heterogeneity of the DNA being transcribed. Hence, it is not surprising that the elongation complex's composition also varies along the way while transcribing a gene.
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After a large-single-celled zygote is produced via fertilization, the process of cleavage occurs while zygotes travel through the uterine tube. Cleavage is a mitotic cell division that does not result in growth. With each round of successive cell division, daughter cells get increasingly smaller.
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Meiosis is a carefully orchestrated set of cell divisions, the goal of which—in humans—is to produce haploid sperm or eggs, each containing half the number of chromosomes present in somatic cells elsewhere in the body. Meiosis I is the first such division, and involves several key steps, among them: condensation of replicated chromosomes in diploid cells; the pairing of homologous chromosomes and their exchange of information; and finally, the separation of homologous chromosomes by...
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Telomere Elongation During Pre-Implantation Embryo Development.

Hyuk-Joon Jeon1, Mia T Levine2, Michael A Lampson3

  • 1Department of Biology and Penn Center for Genome Integrity, University of Pennsylvania, Philadelphia, PA, USA.

Advances in Anatomy, Embryology, and Cell Biology
|July 19, 2024
PubMed
Summary
This summary is machine-generated.

Mammals primarily use telomerase for telomere elongation. However, an alternative lengthening pathway (ALT) is active in some cancers and early embryonic development, utilizing homologous recombination to rapidly increase telomere length.

Keywords:
ALTPreimplantation developmentTelomere

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Area of Science:

  • Molecular Biology
  • Genetics
  • Developmental Biology

Background:

  • Telomeres protect chromosome ends and shorten with each cell division.
  • Telomere length is maintained by telomerase or the alternative lengthening pathway (ALT).
  • Early embryonic development involves rapid telomere elongation.

Purpose of the Study:

  • To explore the mechanisms of telomere elongation in mammals.
  • To investigate the role of the alternative lengthening (ALT) pathway in early embryonic development.
  • To understand how maternal and paternal telomere asymmetries influence embryonic telomere regulation.

Main Methods:

  • Review of existing literature on telomere biology.
  • Discussion of models for telomere regulation in zygotes.
  • Identification of key differences in maternal and paternal telomeres.

Main Results:

  • Telomere elongation occurs via telomerase or the ALT pathway.
  • The ALT pathway is crucial for rapid telomere lengthening in pre-implantation embryos.
  • Maternal and paternal telomeres in zygotes exhibit distinct genetic and epigenetic features, including length and chromatin structure.

Conclusions:

  • Asymmetries in zygotic telomeres likely play a role in regulating telomere length during early embryonic cell cycles.
  • Further research is needed to elucidate the precise mechanisms of ALT pathway activation and telomere regulation in embryos.