Category: Lab Notes

Endoreduplication is a specialised cell‑cycle variant in which cells repeatedly replicate their DNA without mitosis, producing polyploid nuclei. Driven by Cyclin E, CDK2, APC/C–Cdh1 and E2F7/8, this process enhances cell size, biosynthetic capacity and stress tolerance in plants, insects and mammalian tissues.

Asymmetric cell division produces daughter cells with different sizes, molecular compositions or developmental fates. Guided by polarity complexes, spindle orientation and unequal segregation of determinants such as Numb and Prospero, this process maintains stem‑cell pools, drives tissue development and prevents uncontrolled proliferation. Its disruption contributes to degenerative disease and cancer.

Cell‑cycle checkpoints act as surveillance systems that monitor DNA integrity, replication completeness and spindle attachment. The G1, G2 and spindle checkpoints prevent cells with damage or misaligned chromosomes from dividing, ensuring accurate genome transmission and protecting against genomic instability and cancer.

Cell‑cycle genes coordinate the progression of G1, S, G2, and M phases through cyclins, CDKs, checkpoints, and replication machinery. Their precise regulation ensures accurate DNA duplication, faithful chromosome segregation, and controlled cell proliferation. Understanding these genes is essential for explaining genomic stability and the molecular basis of cancer.

The G1/S transition is the critical checkpoint where a cell commits to DNA replication. It integrates cyclin–CDK activity, Rb phosphorylation, and E2F activation to ensure accurate S‑phase entry. Proper regulation protects genomic stability and prevents uncontrolled proliferation.

Meroblastic cleavage is a partial embryonic division restricted to the blastodisc of yolk‑rich eggs. It produces a blastoderm that sits atop the yolk and establishes early developmental polarity.

Holoblastic cleavage is a complete embryonic division that produces progressively smaller blastomeres. It occurs in embryos with low to moderate yolk and establishes the foundation for blastula formation and early developmental patterning.

Embryonic cleavage cycles transform a single‑celled zygote into a multicellular embryo through rapid, synchronous divisions. This article explains cleavage patterns, maternal control, and the mid‑blastula transition.

Binary fission is a rapid and efficient form of asexual reproduction in prokaryotes. It involves DNA replication, chromosome segregation, and septum formation, resulting in two identical daughter cells.

The SCF complex is a modular E3 ubiquitin ligase that targets cell‑cycle regulators for degradation. Its precise control of protein stability ensures accurate progression through the G₁–S transition and maintains genomic stability.

The SCF (Skp1-Cullin-F-box) complex is a major E3 ubiquitin ligase that controls cell‑cycle progression by degrading key regulatory proteins. Learn how Skp1, Cullin‑1, and F‑box proteins maintain genomic stability and drive the G₁–S transition.

The S phase is the period of the cell cycle in which DNA is replicated, producing identical copies of the genome for distribution to daughter cells. It is tightly regulated to maintain accuracy and prevent genomic instability.

Cancer is a multifaceted disease caused by the uncontrolled growth of abnormal cells. It develops through genetic and epigenetic alterations, environmental exposures, and interactions within the tumour microenvironment. Understanding these processes is essential for improving prevention, diagnosis, and treatment.

Genomic instability describes the increased tendency of cells to accumulate genetic alterations due to failures in DNA repair, replication fidelity, and chromosome segregation. It plays a central role in cancer development, ageing, and hereditary disorders.